aj mccormack and son

Sitework - Page 04
The Brew Cabin


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Forum Question Levelling out a floor depression - Rick - Apr 19th 2003
I have a concrete slab on a house that is not flat has a 30-40mm depression, about 6 - 8m², in the centre (ponded when poured by Groundworkers)

I will be laying 50mm of polyurethane then screeding on top as there will be Underfloor heating pipes in screed, I thought that I should try and level out this depression prior to laying insulation. It will allow sheets of insulation to lay flatter and make laying pipes easier. May also have slight improvement on heating response.

This does not need to be structural or even fully bonded. I have had 2 opposite thoughts, the first to make a neat cement grout pour this and allow to self level.

Or 2) lay a 5:1 semi-dry mix, level it out and lay sheets on top when dry.

Any suggestions, which is best solution, or other options?

forum answer Tony McCormack - Apr 21st 2003
You could use floor-levelling compound, although it's a bit pricey, or you could use a simple granolithic mortar skim over the worst affected area. Grano isn't particularly easy to 'feather out', but you could fill the deepest areas with the grano and then use a 4:1 mortar to tidy up the edges. It's not as though it will ever be seen!   smile

Neat cement is nasty stuff. It is so-o-o-o brittle and hard to work that it's not a good idea. Semi-dry would be ok, as long as you get it properly compacted. For small repairs, I would be happy enough to use a semi-dry mortar, but, for 6-8m², I'd be happier with grano, especially for any spots deeper than 6mm. 30-40mm of mortar isn't particularly strong, hardwearing or tough, which is why Grano would be my preferred option.

Apr 21st 2003
Thanks for comments - the hard wearing ability of grano isn't needed though as this will have 50mm insulation and then a screed on top ... so no wear at all.

I did have a comment from a friend to just blind out with sand- but thought that might move about too much before things are screeded.

If I go with semi-dry, would it be worth putting PVA down onto slab first to aid it sticking?

Tony McCormack
Apr 22nd 2003
I wouldn't waste my money on PVA, Rick. If I wanted to bond the topping to the existing oversite, I'd use SBR, as PVA is a bit weak for concrete bonding, but then, I'm not convinced that bonding would be essential in this scenario. It's a basically a 'fill' rather than a structure, and, as long as the 'fill' is solid and not likely to shift, then that's all that's required.

I'd still use grano, though, rather than plain sand and cement mortar.   smile

Apr 23rd 2003
OK - I'm sold I'll use Grano - but having never used this, is it sold in bags - will local Builders Merchants have heard of this?

What mix would I use?

Tony McCormack
Apr 24th 2003
Any decent BM will have it. It's sold in 40 or 50kg bags as 'Grano',Grano Dust, Granolithic  or similar, depending on where you are. There's a mix recipe given on the Mortars page, which will be more than strong enough for your job. A couple of bags should be plenty for what you have to do, I reckon.
May 2nd 2003
I give up, I can't get GRANO - none of local BM's stock it, most had never heard of it.

A distant branch of Jewsons were supposed to have it - but no luck when I got there.

Several BM's advised using 6mm chippings and stone dust (both blue pennant).

So I have some coming tomorrow.

Any advice on a mix for this - should I aim for the same 6:1:2 mix you show for Grano.

Tony McCormack
May 3rd 2003
The 6mm to dust will be fine - same mix, I reckon, Rick.

Maybe there's a market for exporting Grano to the southern regions???   wink

Simeon @ Ronacrete
Jul 8th 2003
I've come across this one quite late into the story but....we make Ronafix, the SBR Tony referred to. It's a white liquid, mix it 1:1 with cement to make a bonding primer. Brush this on to the prep'd substrate, then overlay with a screed (not a grano mix Tony, not needed as will be covered) of - by volume - 1 cement: 2.5 cement : medium grade sharp sand. The liquid is 1:3 Ronafix:water. Add enough liquid to make the screed semi-dry, trowel on the wet or sticky primer, smooth it level, protect with polythene for 24 hours. Walk on it after that time, put the polstyrene board and then continue with your construction after a further 24 hours (all at 20°C).

The above screed mix is OK at >25mm, thinner change to 1:2 cement:sand and change the liquid to 1:1 Ronafix:water. Primer stays the same.

For more info see this PDF document or call us.

Good Luck

Forum Question Laying stone steps - Pauline - Apr 23rd 2003

Does anyone have any ideas about how to shift large stone steps? We are making a set of steps to go from one level to another, a rise of about ten feet, in the garden and have bought some nice old steps, each of which is a metre by 16inches, by 8inch rise. They have been delivered about twenty yards from where we want them (at the other side of the lawn) so need advice on shifting them.

Also how do you get heavy stone into position on wet concrete? Do we need a concrete bed for the steps? We're on heavy clay which is pretty solid.

forum answer Tony McCormack - Apr 24th 2003
What you need is a couple of big, strapping chaps or chappesses, Pauline. Those steps must weigh summat like 200kg a piece, so even two strong persons will have a job on their hands, but it's just about manageable, if they know what they're doing and have experience with hard-landscaping.

To be safe and comply with the Manual Handling Regs, then what you really need is a digger or crane of some sort, perhaps a little mini-digger or a JCB, as that's the safest way to handle these steps, but then, is it feasible to take a machine such as that into your garden?

Bedding the steps - they really do need to be laid on a bed of concrete, as that's the only way to ensure that they are firm, secure and level, and will stay that way.

I suspect that you really need to consider bringing in a professional landscaper or groundworker to help you with these steps, as it's not the sort of job best suited to the average diy-er. One slip, and you could seriously injure yourself, or, god forbid, someone else!

Forum Question Laying out sloping curve - Aidan Dougan - Apr 26th 2003
Hi all,

Love the site, tremendous changes since I first looked couple of years ago. And the forum really gets down to all those details we need to know. Anyway I've built a house and need to get loads of groundwork done, so I'll be hanging around here for a while.

I'm making a drive around my garage to a basement underneath. So there's a curving descending driveway roughly a quarter circle radius 10m. I'd like to get the gradient right. My plan is to mark out the kerblines and divide up each line into say 10 segments with a pole between each. Obviously the outer kerb is longer than the inner so the segments will be bigger. If I then divide my total drop (2.5m) in 10, the level at each pole should be 250mm lower each time. Is that how you would do it? I have a cheap rotary laser which I can see fine at dusk. How would you mark out the radii bearing in mind that the ground is dropping over 2.5m - would you let the tape go to the ground and calculate extra for the drop or try to keep it level by pulling from the top of a hopefully vertical staff?

forum answer Tony McCormack - Apr 27th 2003
This is quite a complex setting-out problem, one that might be assigned to a cocky final-year student, just to see if they really have got the hang of how to do it on site!

To be honest, I can't tell you exactly how it would be done on your particular project, as I don''t have enough information at present, and I'd much rather actually see the site than guess at what it might be like, but I'll talk you through the basics and then you'll have to adapt it to your site or kidnap a passing surveyor! wink

Firstly, the setting out of the radius. For this, you need the origin, but, if that's not available, then you can use a 'chord' method, as explained on the "Obstructed Arcs" page of the Setting Out section. The simplest method is to set out the points on the arcs and then use a vertical staff to transfer the "plane position" to ground position. The points established by swing an arc from the origin, or from a subtended chord, are assumed to be on a flat plane. However, the ground slopes so dramatically on this site that the position of the arc points needs to be dropped below the level of the plane, so you need to ensure you can set out these points 'plumb' (true vertical) from the assumed plane - confused? You will be!!

So, for setting out the arcs (internal and external radii), assume a 2 dimensional flat plane (forward/back + right/left) and then rely on plumb lines (or a vertical spirit level) to transfer position into the third dimension (up/down).

Next comes the problem of establishing the paving level at each required point on the arcs. Let's assume that you've now established the alignment of the arcs and have driven in a number of road pins at regular intervals, and, on this project, I reckon a suitable interval would be 2-3 metres.

The profile for the finished paving will not be what is called a "flat bone", that is a straight line of sight from the top of the access road to the garage floor (the orange line on the sketch), but should be a sine curve (the purple line) which allows a smooth transition to and from the garage and the access road.

steep arc

It is mathematically possible to calculate the level at any point on the arc, but it's much simpler to rely on common sense and 'sighting-in' on site. Once the arcs are established for position, fasten a taut string line from point to point to point and adjust the level of the string at each point to create the profile so that it looks like a smooth sine curve. This will take a good bit of fiddling about - set the level at each point, move around to view it from several angles, adjust it as required, view it again, adjust it again....and so on and so forth until you have a profile that looks about right. When you come to put in the kerbs, you will need to follow the string line as an approximate guide, and then adjust the level of the kerbs once the whole arc has been laid to give what is called a 'sweet' curve. The rule is that, if it looks right, it is right. smile

It's also important to consider what is going to happen to the surface water on this pavement. You need some form of drainage to prevent the garage becoming flooded. You could lay a linear drain across the garage threshold, or a gully at, say, 1 metre away from the grage threhold and 75mm lower than the garage floor, but you must have some method installed before you lay the paving.

Aidan Dougan
Apr 28th 2003
OK Tony, Appreciate the reply.

First as you say, setting out the arcs from the origin. I can set an origin OK and put in a steel pin to attach my big tape. Then I keep it level and mark the start of the first curve at the top of the slope with a peg. After a few more pegs, I'm going to be up on the step ladder dropping a plumb line on a patch of sand to make a mark. Too much wind today for that I think! I've never seen any surveyors up on ladders. Do they use some kind of laser or ultrasonic ranging equipment?

Anyway I can definitely do that part with the steps. Then the levels. The reason I know I need to do this right is as you say, the look. My digger man made a rough shape of the slope and it is useable, but it doesn't look right. (I'll have to get myself a wee digital camera so's I can post some pics - Seems to be essential for the various forums (fora?) I'm reading)

I know you said make a sine curve, but wouldn't that make the grade steeper in the middle. For this length of slope, about 20m in the middle, I was thinking of a "flat bone" as you call it, with some sloping off at top and bottom. I think it will be hard enough to set out a flat bone with unequal side lengths, never mind a sine curve. Maybe If I set out the flat bone and get it shaped to roughly that setting, I could tidy it up with my shovel and rake and a few bucketfuls of screenings.

Regards - Aidan (Digger) Dougan

Tony McCormack
Apr 29th 2003
Aidan asked,
Do they use some kind of laser or ultrasonic ranging equipment?

Almost - they might use a dead fancy theodolite or grandly titled "Earth Station" that can define angles in 3 planes as well as distance, but, if it were me, I'd be using a long staff and spirit level. After all, if it's there or thereabouts, then it's right, as it's a simple kerb line and, if it's grossly out of place, it would soon become pretty apparent!   smile

Seems to be essential for the various forums (fora?) I'm reading

Forumses!   wink

And finally, yes, a sine curve does make it steeper in the middle of the curve, but it's not a lot. However, it does obviate the problem of grounding that would happen if you relied solely on a flat bone from the top of the access road to the garage floor. What you describe, "a 20m flat bone with some sloping off at top and bottom", is just another way of describing a sine curve!   wink

Aidan Dougan
Apr 29th 2003
Thanks Tony,
Thats me sorted on the theoreticals for now. Time to get measuring and digging.
Forum Question Pergola Construction - Melanie Wright - Apr 28th 2003

We are considering building a pergola in the not to distant future and need to get a few things straight before we start planning.

On the "pergola" page your plans suggest a minimal length of 2700mm to create a bay of 1830mm.

  • How have you arrived at this calculation?
  • What side rail overhang has this allowed?
  • Why is there a notch cut out of the side rail?

Apologies if the answers are obvious the grey matter isn't quite understanding.

forum answer Tony McCormack - Apr 29th 2003
I've got to catch the train in an hour, Melanie. Can you hang on until Thursday when I'll have time to go through the technical drawings for that pergola?

It must be 5 years since I did that drawing and I can't recall all the detail, and I'll have to un-archive the original CAD plans!

I've stuck a Post-it on my screen to remind me to check the detail when I get back from my travels.   smile

Melanie Wright
Apr 29th 2003
No problem, we are only at the early stages and are in no rush.

I have another question I omitted from my first post if you wouldn't mind. The top of the posts appear to run level with the top of the crossbeams. Is this the case? If so wouldn't leaving 100-150mm of the post projecting above the top of the side rails (page 4) leave a 25-75mm post projection over the top of the crossbeam (using a cross beam of 100mm depth with a 25mm notch cut out).

Thanks again

p.s On touring many a garden centre I noticed that on a lot of the pergolas built there, the side bars have been slotted into the uprights, having cut out a notch in the tops rather than attaching to the sides as you suggest. Is there a reason you don't favour this option or is it just another way of doing it?

My partner would like to pass on his thanks to you for increasing Jewson's business and parting him from Sky Sports on the weekends. Every since I discovered your website he says he has been a permanent feature in the back garden!!!
I couldn't be happier. Keep up the good work. smile

Apr 29th 2003
Hi all,

Melanie hope you don't mind me using your thread. I too am at this pergola stage (while I search for the patio!!). Now I'm sure the plan on this site is one of many and what you end up with depends on ones taste, but after searching online, I was wondering what was behind the double cross beams in this plan?? Is it just taste?

From looking at the picture, I get the impression that these cross beams seem to be sitting high above the side rails, but again, its probably down to taste.

Cheers - Mike

Tony McCormack
May 2nd 2003
OK, I'm back in the chair now, so I'll work my way through all these Qs....

On the "pergola" page your plans suggest a minimal length of 2700mm to create a bay of 1830mm.
How have you arrived at this calculation?

It is a 'suggested' figure to create overlap between adjacent bays. If you take a side rail that would be used at the end of a run, then you have 150mm for the taper, 50mm of space, 100mm for the post, 1800mm for the bay itself, 100mm for the next post and that all adds up to 2100mm, so there's a 600mm projection into the second bay, if a side rail of 2700mm is used.

What side rail overhang has this allowed?

150 + 50mm = 200mm, as described above.

Why is there a notch cut out of the side rail?

I don't know, and I can't see why I've done that. It's not like that in the full 3D CAD drawing but that flat, 2D representation of the 'components' definitely shows an unnecessary notch. I'll amend that drawing asap.

The top of the posts appear to run level with the top of the crossbeams. Is this the case?


If so wouldn't leaving 100-150mm of the post projecting above the top of the side rails (page 4) leave a 25-75mm post projection over the top of the crossbeam (using a cross beam of 100mm depth with a 25mm notch cut out).

I'm not sure what you mean by "Page 4" - it's all one page to me, as I don't print out the webpages I write (why would I???) but I think I've found the bit to which you refer....from the full CAD drawing, it seems I have allowed for the "extra over" projection so that it can be sawn off flush with the cross member at the exact level rather than predetermine just how much is 'sticking up' and then finding the side rails are 'higher' than the top of the posts (not that it would matter, as who the hell ever sees the top of a pergola 2.2m up in the air??? ) Maybe I need to clarify that point while I'm fixing the drawings on that page.

On touring many a garden centre i noticed that on a lot of the pergolas built there, the side bars have been slotted into the uprights, having cut out a notch in the tops rather than  attaching to the sides as you suggest.
Is there a reason you don't favour this option or is it just another way of doing it?

S'just another way! Pergolas ain't really my thing - I'm much happier laying setts or flags or block paving, but I've knocked up a few pergolas (pergoli??) in my time and this is a basic design I used on a number of projects befdore I was knackered. I'm sure there must be alternative methods of construction that have been designed by a chippie rather than a flagger and are, consequently, better thought out or more pleasing to the eye, but that simple design has worked for me, and, if I can do it, then anyone can!   smile

And then Mike chipped in with....

I was wondering what was behind the double cross beams in this plan?? Is it just taste?

Basically, yes. That's what folk seemed to like, so that's what I drew.

I should, perhaps, point out that I don't have a pergola in my own garden, so don't quiz me too much on what counts as 'taste' when it comes to garden ornamentation. I have clematis and honeysuckle clinging on to a length of old hosepipe suspended from a couple of 3m high wooden posts - that's real class!   wink

May 3rd 2003

tongue in cheek... Can we have a picture of that!!! wink

Cheers - Mike

Tony McCormack
May 3rd 2003
Seeing as there's a break in the rain and my favouritest clematis ("Freda" - a shade-tolerant variety with lovely candy-pink flowers) is at its best just now, it would be my pleasure to oblige....

clematis freda

...the hosepipe can be seen towards the upper right hand corner, behind the Phyllostachys nigra. smile

If you want to see more pictures of my little patch of heaven, have a look at my Garden website.

May 6th 2003
This is depressing,

Am I asking too much for a Builder's Provider to supply tanalised timber with the dimensions 100mmx100mm (4"x4" in the old language)?? I've rang around a couple of places and all they go to is 4x3. This country is so limited in some respects, first the patio and now the pergola. what next I ask ya...

rant over...


Tony McCormack
May 7th 2003
What is it they say about County Clare? Not enough lumber to hang a man; not enough water to drown a man, and not enough soil to bury a man - think yourself lucky you're not that far west, Mike!   wink

What about getting two lengths of 4x2 and doubling it? I'm surprised there's no 100x100, though. It's a common enough size for construction work. I'll bet you can get it in Dublin.

May 8th 2003
Progress update,

Tony, you'd be surprise to know that I found the posts not in Dublin rather Wicklow. I'll probably go with your website design, but I have a few questions:

  1. As the pergola will be a lean two against the house, I need to secure the cross members. Is the easiest option to secure a 4x2 side rail to the house?
  2. As the pergola is just two bays, is there anything wrong with using a continuous side rail spanning the entire length. the 4x2 come in 4.8m lengths.
  3. Because the pergola isnt big, would I need the braces. What support do they add? Also what is the purpose of the spaces? for appearance, or support?
  4. Because a doorway will pass under the pergola is the 1830mm bay length important, can I adjust (+/- 200mm) to meet my needs?
  5. One of the posts needs to go down in the driveway that I havent taken up. How best to dig the hole, ie how to get the first block up, can I drill into the block?

That's all I can think of at the moment,

Thanks - Mike

Tony McCormack
May 9th 2003
I should have guessed Wicklow. One of my family has a joinery business based just outside Ashford.

So, to answer your questions very quickly (as it's after midnight and I'm shattered)....

  1. - Yes - there's a drawing sowhere showing a wall plate.....aaaah! There it is, on the <spit> Decking page.
  2. - No - Keep it simple. smile
  3. - The braces are purely decorative, even in the full version of that pergola. Scrap them if you don't like them.
  4. - Adjust away!
  5. - To see how to get up the first block, have a look at the Repair & Maintenance page.

How's that? Can I go to bed now?? wink

Forum Question I want a dropped crossing - Liam Booth - May 3rd 2003
Hi, how do I go about getting the kerbs outside my house dropped to accomodate for a wider drive.

Thanks - Liam Booth

forum answer Tony McCormack - May 5th 2003
You must ask the Highways Department at your local council, as the kerb, the footpath and the road itself are considered to be their 'property' and they are responsible for any and all works in the public highway. You cannot carry out this work without their consent - if you do, they can compel you to reinstate the highway to its original condition at your own cost and you may be prosecuted.

They'll tell you if it's possible (there are some situations, such as proximity to a junction etc, that render a dropped access crossing undesirable) and they'll tell you how much it will cost for their DLO boys to come around, sup tea and dawdle over the installation.

Some LAs allow you to select your own contractor. This may be a contractor from an 'Approved List' maintained by the council, or any contractor that has the requisite insurance (around 5 million quids), the correct Streetworks Accreditation, and the wherewithal to carry out the work in a professional manner.

Prices vary throughout the country but an average figure woulk be in the region of 500-1,000 quid, or more if there is a lot of footpath to be reinforced.

Forum Question Railway sleepers raised beds - Jamie - May 12th 2003
Help! I am planning on making a raised beds out of railway sleppers - managed to source my sleepers and getting ready to do the work.

Basic shape of the beds is a 5.2m by 5.2m square with one corner cut off to allow a path! Additionally there is a natural slop of approx. 0.6m which bridges the bed. I want to raise the lower area by around 0.75m with the opposite (higher) location only needing a single sleeper.

I found your guide very useful BUT I have a little query. Your guide (and others) talk of the sleepers being laid flat on their broadest edge. I want to lay them flat but on their thinnest edge - i.e. using three sleepers to create a 0.75m high raise.

I was hoping that by linking the down slope sleepers with the side sleepers this would provide the strength to overcome any toppling. Any thoughts?

I was going to use a chainsaw to cut the ends of the sleepers in half so that abutting lengths can be overlapped and pinned together. I was then going to try to use both your suggested methods of joining to attach the sleepers - i.e. drill through (top down) in order to drive a steel rod through all sleppers AND later increase the strength using the steel straps both vertically and horizontally (at the corners). Hopefully with all that I can lay then on their sides rather than on their backs?

Other query was about the concrete foundation. Is there a real need to set the sleepers in concrete? I was planning on simply resting them on the ground (perhaps a slight ditch. I was then going to drive the steel bars down into the ground through the bottom sleeper.

I would really appreciate advice on materials to be used and general approach. Could I screw each sleeper together as well as using the steel rods? If so what diameter to drill at and what diameter screw? Best place to source 20mm mild steel rodding? Is there a difference between this and rebar or are we talking about the same stuff?

General confidence to tell me it should work and I am not going to destroy everything!!

forum answer Tony McCormack - May 13th 2003
You can lay thge sleepers on edge, if you wish. As long as the restraints and ties are strong enough to contain the weight of the contained earth when it's soppping wet, they way you actually lay the sleepers isn't all that important.

If you do as planned, and both pin the sleepers vertically (Good luck drilling through 250mm of sleeper wood, by the way!) and then use steel straps to fasten the front face sleepers to the edge timbers, then that should be ok, but make sure your use rustproof screws at least 75mm in length.

You could omit the concrete foundation, but I think it's a mistake to do so, as it's much easier to settle the base sleepers onto a bed of concrete than to get them firmly bedded onto earth, and then you know that the concrete will hold them firm and help spread the loading, as well as providing a good key for the vertical bars.

As mentioned above, I always used 75mm, 100mm orr 150mm screws with sleepers, depending on what we were doing with them. A pilot hole approximately 4mm diameter was used to guide the screw into the timber. 20mm threaded bar can be bought at most decent BMs and it's not the same as rebar - although you could use rebar to form the vertical bars, as the thread isn't vitally important.

May 13th 2003
Ah - so drilling through 250mm of railway sleeper is going to be tricky then - Was going to try this with a electric Bosch thing - presume this would be foolish? So I guess I would have to hire a more beefy drill?

I am reluctant to got for the flat side down as that will involve buying another 5 sleepers and the project manager (aka wife) is reluctant to release the additional capital!!

Incidentally - What dia should the hole be to drive the 20mm threaded bar? Also in order to get the bar to get through to the concrete base before it goes off I need to do the entire job in a day. Might need a few extra hands then!!

Thanks for the advice - This site is a godsend when it comes to my more bulky garden diy projects. It's a tree house/drinking platform next so I'll be sure to be back in touch for that!!

Tony McCormack
May 13th 2003
To drill trough a 250mm sleeper, you need a decent drill. We have a Bosch 850 summat or other that manages quite well, if you can lift the damned thing up! The drill bit is a nightmare, though, as it's not easy to find a 300mm long 20mm dia wood-chomper. (20mm hole for 20mm threaded bar, obviously!)

When it comes to anchoring the sleepers, if you don't think you could do it all in a day, you could set the base sleepers on the concrete bed, drill through and set the vertical bars, and then leave the rest for another day, as long as you can fairly accurately drill the requisite holes in the right place, and you have a glamorous assistant to help you jiggle the upper-course sleepers onto the protruding bars.

Combined tree-house and drinking platform - Mmm.. that sounds like a really good idea!   smile

Forum Question Concreting around a pond - Peterplay - May 14th 2003
Hi Tony,
I appreciate you don't deal with ponds but my query simply concerns a concrete collar(10"x10") around the perimeter of a pond, before fitting a plastic liner.

I am mixing by hand and will be unable to finish in one day. Would the steel rod method be suitable for jointing the sections please? Pond perimeter 40 feet rectangular.


forum answer Tony McCormack - May 14th 2003
Yep - sounds ok to me, but don't come crying if all your Koi end up floating!   wink

Make sure your starter bars are left protruding by 200mm at least, and leave the surface of the first pour relatively rough so that you get a better 'key', but angle it so that it doesn't hold water during the lay-off.

If it's more than a couple of weeks between pours, you might need to etch the surface of the first pour to ensure good adhesion and get rid of any laitence, but that's the sort of trouble we would normally go to for motorway bridges, not garden ponds!   smile

Good luck!

May 15th 2003
Many thanks Tony, I will have a crack at that.

Won't whinge if my Koi croak - that's up to me to get the water quality right and the Koi will look after themselves. smile

Forum Question Long Access Road - Simeon C - May 26th 2003
I am looking for help, I have a small holding in Scotland which is "far from the madding crowd". This gives me an access road that I have joint maintenance responsibility for that is approximately 500m long. While this is not exactly a road it does irregularly see quite heavy vehicles (tractors and lorries). The existing surface has suffered subsidence to form wheel ruts in the order of 5-10cm. The middle of the track is banked up with loose hardcore (20mm) and since the track is on a hill suffers from erosion of the fine material due to the water flow down each rut (lots of rain in Ayrshire!). Where the track is less steep deep pot-holes have formed. I have seen the example rates per square metre given on your site and quite frankly I nearly choked (3m x 500m x £45 odds = too much).

Is there anything more cost effective I can do, I am not a cheapskate and I am happy to pay for a good job but contracting out for sums this large scare me. If I just get some loads of planings, spread them and give them a quick roll, what sort of performance would I hope to get out of this compromised surface

forum answer Tony McCormack - May 27th 2003
The price of 45 quid per square metre sounds like a price for block paving, which is probably over-specifying for your needs, Simeon. The two simplest options would be to re-grade and regulate with a suitable crushed stone, or to surface with a base course macadam.

Re-grade and regulate involves levelling out what you have and adding to it with a decent quality granular material, such as DTp1. I have a strong mistrust of planings as they tend not to bind and soon allow the potholes and ruts to re-appear. However, they are very cheap and ok for ocassional traffic.

For the blacktop option, you have the reassurance of a surface that should last at least 10 years and won't be washed away or rutted. The existing surface can be re-graded and used as a sub-base, and then a 70mm layer of base laid over the top, for helluva lot less than 45 quid per metre! There's no need for a wearing course on an access track, as you're more interested in serviceability rather than aesthetics.

Invite a couple of contractors around to give you a price. That will give you a clearer indication of what's available at what cost, and then you can decide which is best for you.   smile

Simeon C
May 27th 2003
Tony - Thanks for the quick response, I have learnt loads already from your site (you should probably charge for this!)

I suppose asking a contractor is the best bet.  I must admit I was trying to make up my mind before speaking to a contractor to avoid sounding too green. How much can I expect to pay for a compacted Type 1 solution per M sq? My road is fairly sound despite its erosion. The 'hump' in middle is quite firm underneath the loose stuff that has gathered on top. Should I leave this surface in place in preference to grading the surface and risking more settlement? Alternately is this just a useful source of hardcore to be evenly distributed across the path?

Tony McCormack
May 28th 2003
I'm reluctant to give prices for work such as this, as I'm not familiar with the site, the access or local trading conditions. but a layer of DTp1 laid, levelled and compacted shouldn't cost more than around a fiver per square metre.

If you're re-grading, it's best to level out everything that's there just now, including the hump, and then top it off with new material. Trying to keep the hump in place results in two strips of new material with a central ridge, which can cause a repeat of the pot-holing and erosion problems.

Simeon C
May 28th 2003
That is fine, I understand that it would be asking a lot for you to price a job on the basis of my few uneducated words. I shall opt to get quotes on the basis of a re-grade so that the sub-base is flat followed by the compacted type 1.

When I get comparable quotes from contractors then it should then be clear. Thanks again for your help.

Forum Question Working out the area - Cott66 - Jun 6th 2003
How do you work out square metres of somewere to pave?
forum answer Tony McCormack - Jun 7th 2003
It depends on the shape of the area. If it's a rectangle, then it's simply length multiplied by width. Circles can be determined by using Pi.r², and regular triangles by using half the base times the height, but most jobs require a bit of each.

The easiest way is to plot out the job on a sheet of graph paper, break it down into a series of rectangles and triangles as far as possible and use that to calculate the total area. Of course, if you have a dead fancy CAD system like mine, you simply define an area by clicking on a series of points, and the computer calculates the area for you.   smile

Jun 7th 2003
Pity you dont have a calutator on your site to do it. hint hint. cheers
Tony McCormack
Jun 7th 2003
But you couldn't have a simple calculator, as there's no way of being able to work out all the possible variables without it becoming a CAD program rather than a simple calculator.

If it was simply a matter of calculating rectangles, that would be easy to do as a website calculator, but anything beyond that requires sophisticated input to determine points on the perimeter of the area to be paved, and then relies on complex mathematical analysis to breakdown the enclosed area into a series of geometric shapes. I'm a flagger, not a bloody computer programmer!!   wink

Jun 7th 2003
A simple one would do for people like me who just want rectangles and are a bit thick..ha ha.
Forum Question Concrete Large Shed Base - A Fuller - Jun 11th 2003

What a great site, I was able to copy and paste and edit into my own specification - to excavate and build a 15.5metre x 3 metre x 100mm concrete base for a large shed (actually a garage to be used as a shed)! I become an expert ovenight!

Anyway, I sent the spec to a builder who has done small jobs for me and he came up with a price before seeing the site of £600 to £700, I expect that will be plus VAT.

That actually sounded quite fair to me as I think to do it myself -

  • 3 tons ballast = £150
  • 10 bags cement = £70
  • mixer hire = £20
  • vibrator hire = £20
  • damp proof = £20
  • shuttering timber = £30
...have I missed anything, maybe a small skip for non top soil rubbish (I would re-distribute topsoil)?

So that is at least £310 to do it myself, without a mini digger, add a digger and that is closer to £480.

So the labour part doesn't sound too much, to me.

Have I got something wrong? Do you think the builder's price is fair?

Also, I put into the specification that the front 0.5 metres, which is outside in front of the doors should have a fall of 25mm, the main idea is to help rain move away, from the doors, and also as it is a garden shed, for storing lawn mower, bikes, and a boat, help the entrance 'smooth' in from the lawn making it easier to get into.

25mm was a guess, do you think that is enough or too much?

I also specified a fibreboard joint at the start of the fall, is this OK? And I also specified another joint half way across the inside, hence making 2 main slabs 3m metres x 2.6 metre, I know this is probably not necessary having read this web site, so should I take that out of the specification?

Many thanks

forum answer Tony McCormack - Jun 14th 2003
Your figures seem fair enough. 50 quid for a ton of 'ballast' seems a bit pricey to me, sat here in the aggregate rich North-West of England, where I would expect to pay nearer 20 quid per tonne.

I'm not sure, though, how you've come up with a mere 3 tonnes of aggregates, when you need 4.6 m³ of concrete (15.5x3x0.1) - my calculations suggest you need around 8.5 tonnes of 'ballast' and 1.5 tonnes of cement

The advantage of letting the builder do all the work is that you can sit back and sup a cool beer while they do all the work, safe in the knowledge that they have years of experince that they bring to the job for free.

The fall at the front of the slab is fine. 25mm over half a metre is plenty, but you could increase it to, say 50mm, if you wanted to be extra sure.

As for the construction joints, I really wouldn't bother. Get the builder to order concrete with added fibres, and that will be enough to resist any tensional cracking on this sort of job. If you're planning on using a brick-built structure, or if there'll be any heavy machinery installed in the 'shed', then you might want to consider using rebar, but, for everyday use, poly-fibres will be adequate.

A Fuller
Jun 16th 2003
The builder suggested installing a wire mesh (re-bar) and said it will not cost any extra.

Sounds like he knows what he is doing and is being fair.

As for the 3 tonnes ballast, I forgot to multiply by the 3 metres width! (giving 9 tonnes), that would have been good.

I am even more convinced to let someone else do the work, moving 10 tons of stuff down my garden would definately wear me out!


Forum Question Garage Footings - Brian W - Jun 14th 2003
My current garage is 36ft long which three quarters I have demolished, I was surprised that the concrete base was only 4" thick and the walls (blocks with brick piers) were built on the edges of this base.

I now wish to build a garage approx 21ft long but a foot wider, obviously I want to dig out the footings and do it right.

Again the walls will be in blocks with internal brick piers, my guess is the walls will be 10ft high and a flat roof (probably corrogated sheets).

How wide and how deep should I dig the footings? The ground is a very heavy clay. (in inches please)

forum answer Tony McCormack - Jun 14th 2003
I don't do inches, Brian. This is the 21st century and we in the civils side of the building trade have been metric for over 30 years.   smile

Your slab should be designed by a structural engineer. I can give recommendations and suggestions, but I will not give a specification without seeing full drawings of the planned structure.

A typical 'raft' for this type of project would have 150mm thick keeled toes at the edges, roughly 450mm wide, with a minimum 100mm thick slab. All this would be built over a prepared sub-base with a damp proof membrane, and use fibre-reinforced concrete with a compressive strength of not less than 20N/mm² - that's just a suggestion, of course!   smile

Brian W
Jun 14th 2003
Thanx but it doesn't help much frown

The garage is 6.5 mtrs long by 3.33mtrs wide what I need to know is how big should these footings be to support the walls? Estimate will do just a rough guide so I can get rid of a skip or two.

Tony McCormack
Jun 15th 2003
For a single skin wall - 300mm wide, and for a double skin wall (225mm brickwork) then a 450-600mm wide footing will be required.
Brian W
Jun 15th 2003
Its a single Skin (Block) wall, so far I have dug the footings 260mm wide x 360mm deep (flipping hard graft this weather I can tell yer).
Tony McCormack
Jun 18th 2003
For a single skin construction, the usual recommendation is 100mm spread either side, which is where the figure of 300mm comes from. The depth depends on when/if you reach a decent clay on which to pour the footing, but the top of the footing should always be at least 150mm below ground level, just for frost cover.

For a garage, I would suggest that you really do need to dig down to a decent sub-grade and then pour your footing. That may be 600mm or more down, but there's no point pouring a foundation on suspect ground.

Brian W
Jun 19th 2003
I have dug down (through heavy clay) and the ground is so hard now I cannot cut through it with a cutting spade. So I was going to leave them at that depth but perhaps widen them a touch.
Tony McCormack
Jun 19th 2003
As you're already 360mm deep, if you pour a 150mm thick footing, then you'll still have 180mm of frost cover, so you should be ok.   smile
Forum Question Installing a sub-surface sprinkler system - 10drc - Jun 16th 2003
I have an existing interlock driveway and need to setup a few sprinkler heads for a 5ft greenway between the two existing interlock driveways.

What is the best method to tunnel underneath the current drive (18') to allow for lines to be run to accomidate the supply lines for the sprinkler heads I wish to add. I really don't want to lift the pavers but wanted to get an idea what in recommended in this situation.

Please advise

Thanks - 10drc

forum answer Tony McCormack - Jun 18th 2003
There are a few "No-Dig" systems that can create a tunnel for you, but the cost may be prohibitive. Most companies offering such a service have a minimum charge of around 800 quid - is installing a sprinkler really worth that sort of money?

You should be able to find contact details for "No Dig" contractors in the Drainage section of your local Yellow Pages.

Other points to consider - will you need frost cover for the water pipes? If laid at a shallow depth, they could freeze, expand and burst if we get another cold winter. A domestic water supply is always laid at a depth of 900mm for this reason.

Lifting and relaying pavers is actually very easy and, if you plan to DIY, then it should be possible to lift a strip of pavers, dig the trench, lay the pipe and  then reinstate the pavings in just a day.

If it were me, I'd install a duct, at least 100mm diameter, and use that to feed through the water service pipes. The advantage of using a duct system is that you can feed through power cables or any other pipes/cables as you need, without having to touch the driveway again.   smile

Forum Question Raising a DPC - Rob Stedman - Jun 20th 2003
I'm considering whats involved in laying a patio at the back of my house. Thanks for the info on your site - it certainly helps. I'm a novice and have a lot to learn!

I think the DPC in the house wall at the rear needs some attention - currently its only 70mm above the ground level and the rear garden slopes upwards aways from the house. I think the patio area needs digging out to increase the DPC height and allow drainage away from the house.

A neighbour suggested that I could avoid having to dig out this area by building low (I guess 200mm or so) wooden formers at the base of the house walls and pouring in 'a good strong concrete mix'. Then remove the formers leaving a concrete cladding around the lower walls.

Is this an acceptible practice? I've not heard of this before or found anything about this one your site (or others). Or is there another way (short of actually putting in a new DPC which sounds expensive).

Thanks for any advice - Rob

forum answer Tony McCormack - Jun 20th 2003
It's not an acceptable practice to my knowledge, but then, a lot of what architects come up with is beyond my ken and it wouldn't surprise me to find that this notion of casting a concrete plinth against a building had been shown in theory to act as an effective dpc. However, I'd save my energy and my money and not get involved with an experimental numpty idea.

There are three other options that may interest you. The first is the simplest, which is to install a dry channel arrangement against the wall(s), as shown on the Dealing with DPCs page. This reduces the amount of excavation required from yourself and is a straightforward, effective solution.

Alternatively, Option B involves reducing the level of the patio so that you create a gap of at least 150mm between the paving surface and the dpc. Obviously, this involves a good bit more digging and waste disposal, but, depending on the exact layout you have there, and the way you'd like the finished patio to look, it could be a viable option.

Finally, there's the 'full monty' option, which involves getting a DPC specialist around to inject a new dpc and then you'd be able to re-use the existing levels, as you like, safe in the knowledge that your house is fully damp-proofed and your bank account is empty.

If it were me - it'd be Option 1 and in the pub by dinner time!   smile

Forum Question Vertical sleepers for patio retainer - Brian W - Jul 8th 2003
Hi Tony

I am planning on using railway sleepers on end to support a patio over a 30" lift. Is is advisable to use membrane and drainage as per a retaining wall or will the gaps between sleepers provide sufficient drainage. Do you advise the use of a backfill that will allow drainage e.g. shingle or crushed stone.

Thanks in anticipation

Brian Whitehead

forum answer Tony McCormack - Jul 9th 2003
I'd use a membrane to prevent the fines in the bedding and/or the sub-base layers being washed through, causing settlement of the patio in the longer term, but I don't think any sub-base draiange system is necessary, from what you say.

Any good sub-base material should be satisfactory, as they allow reasonably free passage of groundwater. I'd be wary about using a limestone, as that could cause leaching of soluble calcium carbonate through the sleepers, which might begin to look unsightly after a few years, but any other inert material would be fine.

Forum Question Concrete Fence Posts - Rick - Jul 10th 2003
I have to put in a lot of fencing, a planning condition. To save having to redo this in the future I'm intending using concrete H posts and gravel boards and fix wooden fencing (build on site) between. (aprox 48 posts + ends and corner post)

The question is on practical points of putting them in the ground. One guy on site has just done this, he digs the holes then puts 4" or so of concrete in the bottom with a couple of rebar off-cuts sticking vertically up. Then at a later date, after concrete has set, he stands in the post, then using a line from first and last post, accurately marks off the post and then cuts off the excess few inches with a disc cutter, after which he then concretes in place.

Is this normal? Seems a lot of work but he advises this is the professional way to do it.

Second question is is there a simple way /technique to keep them upright while concrete sets as these are 8' posts? I can see that a lot of 4"x2" would be needed to hold a post upright. I don't have loads of 4"x2" so it would mean only 2 or 3 posts at a time - very slow.

forum answer Tony McCormack - Jul 11th 2003
Fencing contractors have their own ways of working, but the method you outline worries me slightly.

Putting a spadeful of concrete in the base of the hole is fine and something we've always done to ensure the post doesn't 'settle', however unlikely it may seem when you consider all the surround concrete. However, sticking in a couple of rebar off-cuts (for those who don't know, rebar is steel reinforcing bars, usually 12-25mm in diameter) is, IMHO, going over the top, and I'd be concerned that the rebar wouldn't always have the minimum 50mm of concrete cover that's needed to protect it from aggressive groundwater. If, for some reason, there's insufficient cover of the rebar, then it will start to rust, which results in a volume expansion, leading to concrete cracking. It may be that the rebar penetrates the concrete pad and is in direct contact with the ground beneath, or it my 'fall over' during backfilling and again be exposed to groundwater which could, possibly, lead to rusting and subsequent cracking of the concrete.

I have a similar-themed problem with the cutting-down of the concrete posts. These post contain a token gesture of 6mm mild steel rebar and if they are sliced and the steel exposed to the atmosphere, then we have the problem of rusting and concrete cracking once again. If the sliced end was fed into the hole and then completely encased in concrete, that would be acceptable, but having the sliced end at the top, as it were, is a bit naughty.

Most of the fencing contractors with whom I've worked rely on digging an over-deep hole, placing a shovelfull or two of concrete at the bottom to enable the whole post to sit at just the right level, and then, as soon as alignment is confirmed, backfill with concrete immediately, so that there is no construction joint between the pad concrete at the base of the hole and the surround concrete.

When it comes to bracing the posts for the first 24 hours or so while the concrete hardens, you can use almost anything - no need to use 4x2 specifically. If the gravel boards are fitted as the posts are placed, then they tend to ensure verticality and alignment on the posts in the longitudinal section (along the fence line) so all you need to worry about is the transverse section (across the fenceline) and any two sticks lashed either side of the post and held fairly firmly by the ground will do.

On larger jobs, we've used 2m lengths of rebar at 46-60 degrees to the posts, with one end driven into the ground and then a cable tie or steel tie-wire to lash t'other end to the post. A day later, we go along and strike the bracing, throw it on the back of the wagon and use it again on countless other jobs.

You could use 2x2, pipe-spacers or any other bits and bats you have lying about. As long as they are reasonably firm and strong enough to support a post in a light breeze, that's all that matters.

Jul 11th 2003
Thanks - the guy on the site measures the posts - as mentioned, and then cuts that amount off the bottom. It is embedded in concrete - the off cuts of rebar are used to give strength between the initial base concrete and the backfill which is some days later.

I did ask why and he is doing it this way as he does not want post 'sinking' in time which he has witnessed when posts are packed up with brick or tile prior to back filling.

Nov 15th 2003
Just as an addition to this thread, I use roofing baton as a support for newly positioned 4" or 3" uprights.

Position the uprights on a bed of 4 - 6" muck, then back fill as soon as you have the right levels with a lean mix. Tamp down as you go (obviously a two man job) and make sure you haunch the top so the rain will simply run off.

Cheap as the proverbial using roofing baton.


Nov 21st 2003
Hmmm. I'd be wary of chopping off the tops of the posts. The reinforcing rods DO rust and I've seen posts with rusty streaks running down the sides and the concrete 'exploded' at the top.

Why not dig deep holes to the right depth (get 2' - 3' in the ground) and then use a very dry mix ? That way, you generally don't even need to have supports while the concrete is setting...

Works for me!


Tony McCormack
Nov 23rd 2003
I mentioned the problem with sawing down concrete posts in my earlier answer in this thread. It's best avoided, but, if it has to be done, it's better to sit the sawn end in the hole, encased in concrete and therefore protected from the atmosphere, rather than have it at the top, exposed to the elements.

A dry or semi-dry mix is standard for fencing erection. I know some folks like to make a meal of it and use a 75mm slump concrete, or put the hose onto the hole once it's backfilled with the dry/semi-dry mix, but there really is no need. There's usually sufficient moisture in the concrete and the surrounding ground to initiate hydration/curing, and it's not as though you need a concrete that's rock hard - as long as it's firm, and holds the post steady, that's all that's required.

Forum Question Concrete specifications - Tony B - Jul 11th 2003
I'm pricing a concrete raft floor for a stable block that's causing a few problems as the spec requires RC40 concrete.

I can order RC40 ready-mix but would like to know what it is to see if it's cheaper to knockup on site. I've searched on Google and while there are plenty of references there don't seem to be any specifications.

Any info or pointers gratefully received.

Love the site - loads of real info

forum answer Tony McCormack - Jul 14th 2003
It's not the sort of mix I would want to knock-up on-site, not for a raft! A couple of barrowfuls, perhaps, but owt more than a cubic metre I would buy-in without thinking about it twice.

You probably know for yourself all the problems that happen with large volumes of concrete knocked-up on site - no two batches are the same: they've either got variable cement content or variable water content, but the end result is a patchy concrete and a saving of around 5 quid a cube.

If you buy from a Ready-mix plant, preferably one of the QSRMC accredited plants, then you get consistency of material, easy placing (squirting it in from the back of the wagon), the opportunity to incorporate useful additives, such as crack-reducing fibres, retarders, etc, and, most importantly of all, a guaranteed quality. Then, if owt does go wrong with the concrete, it's not going to damage your pocket as the Ready-mix supplier would be responsible (assuming you hadn't ballsed-up the placement or addded extra water, etc).

An RC40 mix is identical to the C40 mix detailed on the Concrete Mixes page but with added reinforcement. Do yourself a favour and buy-in Ready mix!

Tony B
Jul 17th 2003
Thanks for the reply, I've costred it both ways and the ready-mix is much cheaper with the benefits you've outlined - fingers crossed we get the job now.


Forum Question Levelling a steeply sloping garden - Jim Calbert- Jul 12th 2003
I moved into a brand new house about 5 months ago. When my wife and I first viewed the property we were put off by the rear garden as it sloped up and to the rear corner. We were offered such a good deal on the house that we ended up buying it. Now we're ready to make it a level garden. The lowest point is right up against the rear of the house where there is a small patio. To the side and rear there is a (shared boundary) 6' high wooden fence that I fear might be undermined if I start digging around near it. I know I'll need a retaining wall in the rear corner that will start at the lowest point about midway from the house to the rear fence. We've had a few small-time professional landscapers have a look at it for an estimate and my questions are:
  1. If I start it myself, how far out from the fence should I start digging to ensure it won't be undermined?
  2. In order to get a good estimate should the landscapers be using any special tools like one of those surveyor things on a tripod to figure out how much dirt will be needed to be removed and the hight of the retaining wall? Or should I just rely on them "eyeballing" it?
  3. Do you thing drainage will be a problem?
My garden would be much lower than all the other gardens that border it. Could doing this make mine a swamp?
forum answer Tony McCormack - Jul 14th 2003
  1. - keep at least a metre away from the fence, preferably 2 metres, However, if you're installing temporary shoring as the dig progresses, you can get to within half-a-metre.
  2. - Theodolite is the word you're looking for, or an automatic level at least! Whether your contractor chooses to use one is their decision but you need to determine whether the price they state is a firm quotation regardless of the actual volume that has to be shifted, or whether it's one of those estimates that have a way of doubling once the work is underway.
  3. - The drainage probably will be an issue and I'd look at installing a land drain or composite panel at the rear of the retainer wall to deal with the inevitable inflow from the higher ground. Any contractor that doesn't mention this is probably best avoided.
Jim Calbert
Jul 15th 2003
What would temporary shoring look like? Something like posts driven deep into the ground before-hand?
Tony McCormack
Jul 18th 2003
Posts and sheets of plywood would be one way of effecting a temporary shoring system, as long as the depth of excavation isn't too deep. The posts would need bracing to prevent them being forced back by the weight of earth they're holding-up. If you've more than a metre or so to go down, then I'd consider using temporary steel piles which are not all that expensive to hire but do need to be driven into place with a big digger (such as a JCB), and then extracted with the same at the end of the job.
Forum Question Concrete over concrete - SCMG - Jul 19th 2003
Can you give me some advise please?

I have an outside concrete area approx 6 inches thick 10m x 10m. The finish is a very rough finish. Ideally I want to concrete over, build a gentle slope for drainage, and have a smooth finish.

Am I able to reconcrete over, old concrete, and do I need a compound over the old concrete first?

Many Thanks - Chris Glass

forum answer Tony McCormack - Jul 21st 2003
You could use a granolithic topping to give you a relatively smooth surface that's hard-wearing and capable of carrying vehicles. The grano (as it is called for short) would need to be at least 25mm thick and, ideally should be bonded to the old concrete with SBR or similar.

The old concrete needs to be 'etched' which involves washing it down with hydrochloric acid to ensure you have a clean, laitence-free surface. Then, the surface should be primed with SBR and the grano screeded over the lot before the SBR dries. All these complicated sounding building materials are readily available from a decent Builders' Merchant, and possibly from Travis Bloody Perkins, too!  ;)

The grano mix is described on the Mortars page and details on the coverage rate for SBR and Acid Etching Fluid is given on the containers (from memory, it's around 4m² per litre, so you'd need at least 25 litres)

Forum Question Which mortar? - 99a - Jul 24th 2003
Why lay bricks with morter soft sand and slabs with sharp sand? Can you lay slabs on to a concrete mix ?
forum answer Tony McCormack - Jul 28th 2003
Building sand (aka 'soft' sand) has a higher clay content making is more 'workable' when used as a mortar. Sharp sand has less clay and is therefore better draining, and less susceptible to being washed away, which is useful for pavements that are subjected to regular inundation.

You can lay flags/slabs on concrete, if you wish.

Forum Question Fence post spacing - Mr X - Aug 5th 2003
How far apart should the posts on closeboard fencing be, please?
forum answer Tony McCormack - Aug 6th 2003
1.8-2.0 metres.   smile

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