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 ruler
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Forum Question Setting out Herringbone Pattern - Feb 27th 2002
I've been reading about setting out the 45 degree pattern for block paving, using the string line and having the pattern running the length of the drive for best appearance.

I would like to do this but the trouble I have is that I have a big drive (nearly 100 square metres in all ) and it is isn't square or rectanglar. It starts narrow at the entrance and then widens like a V and has a slight slope up to the house (ideal for drainage). Here comes the tricky bit for me, the house is off set at an angle to the length of the driveway and if I worked off the house as a base line guide the pattern would run transverse across the length. What I have got is a 10 metre length of edging to the right hand side of the drive which could be used as a base line for the pattern to work off. This extends from the entrance but doesn't extend right up to the house, it falls some 10 feet short. Should I run the pattern off this edge and use the string line as a guide to take the pattern up to the house? The other thing is where should I start off,at the entrance, half way along the edging? Something tells me I ought to look to work away from the house down the drive but with the awkward angles I am frightened of the pattern looking skewiff.

Maybe I ought to be looking at another pattern.

Can you help please?

forum answer Tony McCormack - Feb 27th 2002
Choosing a base line to work from is something that has to be done on a job-by-job basis. It's a doddle when your house is square to the drive and that's square to the road, but when you have a less orthodox setting, such as you describe, there are two possible resolutions that seem to work in the vast majority of cases; choose to work from a line of sight that presents the best view of the pavement when approached from the entrance or select a base line that aligns with the house itself.

Now, if you decide to go with the house option, then it's simply a matter of selecting the longest edge as a base line and extrapolating that as required. With an entrance aligned driveway, again the longest edge is used. However, when you have a drive entrance that is not parallel, as you describe, you have a further complication - do you align with the right hand edge, the left-hand edge, the centreline, or perpendicular with the public footpath/roadway?

Without being familiar with your layout, it's not really possible for me to say which would work best for you, but what you could do is sketch a rough layout of the driveway and the house on a sheet of A4 paper and then cut out the outline of the driveway. Lay this sheet over another sheet of A4 on which is printed a herringbone pattern, and rotate until you find an alignment that, to your eye, looks most pleasing. To help you out a bit, I've uploaded a gif file that you can grab and that should print out as an A4 sheet at 1:100.

Having said all that, I still reckon one of the two options mentioned above is likely to turn out best.

Switching to another pattern will not make choice of alignment any easier, as all patterns are based on rectangles, so the same problem crops up whatever you choose. However, as mentioned on the Block paving section, a herringbone pattern gives full pattern interlock, and so is much, much, much better for driveways.

HTH

 ruler
Forum Question Alignment of Stretcher Bond - Rob - Feb 27th 2002
We are laying block paving over the entire area in front of our house. The front of the house and both side boundaries are all square relative to each other however the road in front of the house and the front wall are not parallel to the house or square to the left and right boundaries. As one looks at the house we are laying a stretcher bond that runs from left to right. If the block courses are laid such that they are parallel to the front wall/road then they strike the house at a slight angle and visa versa. I appreciate that this is an aesthetic choice however which would be normal practise, should the courses be laid parallel to the front wall/road or to the house?

Thanks

Rob

forum answer Tony McCormack - Feb 27th 2002
Hi Rob,

with a stretcher bond, it will look best laid square to the house thereby striking the threshold with the public highway at an angle. If you do it t'other road round, it looks bloody wierd when you come out of the house, as one of my neighbours who "knows it all" has since discovered.  wink

And why stretcher bond? A herringbone is best for driveways, as you get a full interlock.

Rob
Feb 27th 2002
Thanks for your reply. I strongly suspected that this was the case. Our block pavers are trying to persuade us otherwise (having already laid about 30 sq. mtrs. of blocks parallel to the road). In retrospect perhaps we should have gone with a herringbone pattern however the blocks we now have are Marshall's Tegular traditional in three different sizes and so I presume herringbone would now be impossible. Thanks again.
Tony McCormack
Feb 27th 2002
Tegula/Drivesett can be laid in a herringbone pattern, but it actually looks best laid stretcher bond, so at least your gang got that bit right. smile

I assumed you were using keyblock or similar, which is best in a herringbone. If you're not happy with the pattern they've laid to date, get them to redo it - you have to live with that paving for a long, long time, and it's easier to lift and put it right at this stage than wait for them to cover the entire driveway, cut it in and compact.

 ruler
Forum Question Cleaning my drive and sealing surface - Matt - Feb 28th 2002
I'm considering the cleaning and restoring of my block paved driveway, It's been down for 5 years and has several unsightly areas of moss and staining which makes the whole thing look tardy. I have been looking around for a mild chemical cleaner or acetone to aid in the process as I will be pressure washing the entire area as well in hope of a good result. Can you recommend any such products that maybe of some help? Also I was considering sealing the drive after re kilning to avoid any further staining and moss growth, Is there any particular sealant you could advise use of?....as ever Tony thanks for the continuing help your site provides.....matt
forum answer Tony McCormack - Feb 28th 2002
Hi again,

you don't really need any chemical cleaner; in most cases, simply power washing will return the paving to it's best, but, if you have bad staining, a degreaser such as Jizer or plain wash-up liquid will do as good as anything. Acetone is useless, unless you've spilled paint or nail varnish!

Many of the so-called 'paving cleaners' contain weak hydrochloric acid plus a detergent and some perfume. The HCl works by eating away at concrete pavings but has no effect on clays. The detergent is ok and the scent/perfume is a waste of time and money. Be VERY, VERY careful if using these, as they can irreversibly alter the colouring of concrete pavings by reacting the HCl with the Iron Oxide of the concrete dyes. Test on a hidden corner first.

Once the drive is clean and has be re-sanded to fill the joints, have a look at Resiblock 22 as a sealant. It ain't cheap, but it's certainly one of the best paving sealants available. More info on the Sealants page.

Dexter
Feb 28th 2002
Why is Resiblock 22 so much better then say Thompsons water seal or the like??
Tony McCormack
Feb 28th 2002
Well, Resiblock themselves can answer that on their website, but, to paraphrase....

  1. - it's been developed especially for use on block pavements rather than a 'jack-of-all-trades' product like Water Seal.
  2. - it's a SPPU rather than an acrylic
  3. - it binds the jointing sand as well as seals the surface.
  4. - it has been extensively tested in the most aggressive of conditions, including airport runways.
  5. - it should have a lifespan greater than an acrylic, possibly twice as long or more.
  6. - it comes in a variety of finishes including gloss, satin or matt, to use paint terminology.
  7. - it's used by the trade for the trade, whereas Water Seal et al is more of a DIY solution.

Have a look at the Resiblock website
 ruler
Forum Question Sub-base for Beamish Cobble driveway - Mark - Feb 28th 2002
I'm looking to extend my driveway to accommodate 2 cars, and I want to block pave with Armstrong cobbles, no problem there I hope?

I have had quotations from 3 companies quoting for a concrete sub base, and cobbles set on a Sand/cement screed. However another co is suggesting I would be best to go for the Geo-textile base Geo-Grid for reinforcement, then Granolithic Screed.

I am somewhat confused and noting the latter is some £400 more expensive, I need convincing this is the best option. Can anyone help?

Many Thanks

forum answer Tony McCormack - Feb 28th 2002
Hi Mark,

the cobbles you refer to are the rounded beach cobbles, aren't they?

These are often laid in a sand/cement matrix, as illustarted on the Duckstones page, but the grano is a better medium, as it's much harder wearing. However, it needs to be carefully batched when mixing to keep it all the same colour when cured.

Just what the geo-membrane is for, I'm not sure, unless you're on really, really crap ground. The spec I would probably opt for is 100-150mm of C20 concrete with 25-75mm of grano screed bonded to the top and the cobbles set into that.

Has the contractor offered an explanation of why the geo-membrane is necessary?

Mark
Feb 28th 2002
Tony, thanks for the info.

just to confirm the "cobbles" are Armstrong "Beamish Cobbles", more of a "round edge" 60mm block,rather than as described in the duckstones section.

The ground is fine, and as suggested everyone else I have spoken to suggests a 150mm concrete base would be ok, it was just this one contractor who suggested that the concrete would crack and that we would get drainage problems.

He suggested this GeoGrid as a way to bond/hold the compacted hardcore together as the best option for longevity and drainage, as for the Geo textile, I'm not convinced myself.

I,m thinking of just going ahead with the Concrete sub base with the Beamish cobbles/blocks set on sand/cement screed 50mm, as has been quoted, saving me 400, is this the best option Tony ?

Many Thanks
Mark

Tony McCormack
Feb 28th 2002
Hi again,

so, they're a block, are they? Just goes to show what a nightmare paving terminology can be! I must update my library with Armstrongs products.

I'm not familiar with this exact product, so let me check it out before making further comment on the best laying method. However, the comments made about geo-membranes doesn't hold water, to coin a phrase.

Geo-grid can be used to stabilise sub-grades and sub-bases, but it tends to be used on large projects that will be subjected to exceptional stresses, or over 'made-up' ground. If a proper sub-base material is used rather than the rather unspecific "hardcore", there should be no need for a geogrid beneath a residential driveway.

And just how it is supposed to help drainage? I've absolutely no idea. A concrete or other cementitious bedding medium will be more or less impermeable, so what use is a geo-membrane at the interface of the bedding and the sub-base? I wonder if he means a drainage composite?

Anyway, I'll take myself off to Armstrong's website to learn more about what passes for cobbles up there in the north-east.  smile

Mark
Feb 28th 2002
Thanks for the info. Appreciate your time and effort. Sounds like the geogrid/ membrane are superfluous to our requirements and obviously more expensive.

Best of luck with Armstrong's website.
Mark.

Tony McCormack
Feb 28th 2002
It's not very good, is it? You'd think they'd at least have pictures of their products!! Still, that's what happens when you pay nerds with no understanding of the building trade to build your website.

I spoke to them on the 'phone and they promise info in the post tomorrow. Mmm. We'll see.

...the next day...

The info, sparse as it is, arrived from Armstrong in this morning's post. The Beamish Cobbles are their attempt at a natural sett-like paving block, similar to the Rialta range from Marshalls or the Ionica from RMC. They are laid in the same way as those two better known ranges, ie, as part of a flexible system, just as described on the block paving page.

Quite why you're being told to use a concrete sub-base, I'm not sure, unless there are problems with bad ground, but the spec I would suggest is for 100-150mm of DTp1, with a 35-50mm bedding course of grit sand and then the Beamish Cobbles, laid hand-tight in courses.

If you have any specific queries about the blocks themseklves, the guy to speak to is Mark at Armstrong's Paving Block division in Consett. Telephone number is 01207 505655 or email . If you have any other questions about the construction method, you're welcome to post back here.

If you go ahead with the work, I'd like to see pictures of the Beamish Cobbles when they're laid. smile

 ruler
Forum Question Damaged Clay Pavers - Joe - Mar 1st 2002
We had our drive blocked using clay pavers 8 months ago. I have noticed that on a number of the blocks the edges have broken off. This is mostly where the car wheels have drove over them. Is this something I should be concerned about?

Joe

forum answer Tony McCormack - Mar 1st 2002
Hi Joe,

this sounds ominous - are the edges definitely chipped/spalled?

Most clay pavers have chamfered edges which helps prevent spalling of this nature - are your bricks chamfered or square-edged?

The reason why this happens is that the bricks move slightly when trafficked and by pressing too tightly against their neighbours, the pressure is concentrated on the edges, which then 'spall'. This, I stress, should *not* happen on a properly laid clay brick pavement, which suggests to me that there's summat amiss with your driveway.

The most common reason for this sort of behaviour is that the contractor has either used an inadequte sub-base, or has omitted it completely. The sub-base is the load-bearing layer of the pavement, and it is absolutely essential as it ensures the individual bricks are capable of carrying the weight of cars, vans or foot traffic, without being forced into the ground beneath.

Do you recall a sub-base leyer being laid? It should be a layer of crushed stone at least 100mm thick, on which is laid the bedding sand and then the bricks themselves.

Take a close look at your drive in the daylight tomorrow - are the bricks chamfered or square-edged? Are the joints filled with sand right to the top? Is there any sign of 'ruts' forming where the car runs over the paving everyday? If you can provide me with the answers to these questions, I'll be able to give you more of an idea of what is happening.

Joe
Mar 1st 2002
Hi Tony, Thanks for replying

The blocks are chamfered on the very edge. The sub-base used was mill-waste, and it looked quite deep, probably at least 100mm. This was compacted with a wacker plate. As for ruts, yes there is one by the public footpath. It's quite obvious when it's filled with rain. I'm finding more freshly chipped edges each week. Most are 10-15mm across and about 3-5mm deep, although a couple are 10mm deep.

Joe.

Tony McCormack
Mar 1st 2002
Hi again Joe,

I'm not sure what Mill Waste is, as it can mean different things in different parts of the country. Up here in NW England, we call it quarry waste, and it's not always suitable as a sub-base material. With quarry waste, here's no spec governing the proportion of fines to lumps, so you can, theoretically, end up with a load that has no fines or is all fines.

I'm not quite clear on what you mean when you say "Most are 10-15mm across and about 3-5mm deep" - what are? The joints?

It sounds to me as though the sub-base is settling/moving and that is what is causing the bricks to spall. There's no easy solution to this problem, I'm afraid. In some cases, sealing the surface can prevent further movement, but in most cases, the only real fix is to lif the lot, get rid of the rubbish sub-base and start again with genuine DTp1 on a geo-membrane, if necessary.  sulk

 ruler
Forum Question Choosing a Block - Ric Short - Feb 28th 2002
I've just spent the last hour looking through your excellent website, but I've also spent the last few months trying to decide on which type of block paving to use for my new drive. There are so many to choose from and I find it difficult to imagine the finished product. Do you know of any links that have design ideas/plans etc.

Ric Short North Lincolnshire

forum answer Tony McCormack - Feb 28th 2002
Hi Ric,

all the manufacturers publish brochures/catalogues illustrating their products in the best possible light. use the contact details on the Links pages to get in touch with the various manfs and they'll send you a copy of their brochure in the post.

However, choosing block paving from a catalogue is not the best way - what looks superb when just laid and under special lighting, doesn't look quite the same 3 or 5 years down the line, on a wet Wednesday in November. The best way to choose is to look around and see if you can spot a drive or pavement that you like, and then find out which product(s) have been used.

Hopefully, by the end of this month, I'll have a portfolio of different block types from all the big manfs ready to upload, and you will be able to compare and contrast on this site, but I'm still waiting for one or two of the luddite tendency to confirm their agreement in writing.

What sort of blocks interest you? Plain rectangles? Summat a bit fancy? Olde Worlde? Colourful? Tell us your ideas and I'll see if I can narrow down the choice a bit for you.  smile

Ric
Feb 28th 2002
Thanks for your speedy reply to my query about types of blocks etc. I have a red brick house so don't really want red blocks for my drive, I would like some sort of contrast. I'm looking for something a bit special and not your average concrete block. Your website suggests clay pavers are a good choice as they do not fade. Can you suggest anything to fit the bill.

Many thanks, Ric.

Tony McCormack
Feb 28th 2002
There are over 1200 clay pavers in my database, Ric, so I'm sure we could find something. Is there any chance of you emailing me a photo of the house so that I get some idea of what would look best?
Ric
March 1st 2002
Sorry for the delay I've been trying to e-mail a photo of my drive for you and I've failed!!! If it's any help my property is constructed using a very common brick (so I'm told) made by the London Brick Co. The colour of the brick is predominantly red. I'm open to any suggestions whether it's blocks, clay pavers or anything else for that matter.

Ric

Tony McCormack
March 1st 2002
If you decide on the clays, I'd suggest choosing 2 contrasting colours, say a red multi and a blue, and then creating a design that gives a unique look to your driveway. For something really special, the Fisher Paving from Marshalls might be worth taking a look at.

However, if you want to choose a concrete block, there are some intriguing pavers from Charcon incorporating recycled blue or green glass. For a different look, try hunting down the Fanfare or Agora from RMC, or the Penta or Tallis ranges from TopPave.

If it's olde worlde, then Marshalls' Drivesett is a leader, along with Priory from RMC or Antique from TopPave.

Have you got your hands on any brochures, yet?

Chris Wood
October 8th 2002
I'm having similar problems in choosing a suitable block type for my drive (55 sq m).

My wife doesn't like the supermarket car-park look of standard brick paviors (or the way they fade), and wants something a bit different. We'd probably prefer those rumbled blocks, but they are expensive regardless of the manufacturer - possibly more than I'm willing to pay.

You've said previously to go out and find a real drive that you like the look of,rather than the ones in the brochures. The trouble is that I've never seen one in real life that I've liked particularly - they never look as good as those in the glossy pictures!

So you can see I don't know what to choose. Ideally I like something slightly cobbled or rumbled looking, doesn't fade and won't cost a fortune. I know that you're probably trying to remain agnostic towards the manufacturers, but I need help - can you suggest something?

Chris Wood

Tony McCormack
October 13th 2002
Sorry for the delay in replying, but I've been away for a few days.

For colour fastness, you need to choose a clay paver, but these are often slightly more expensive than a concrete. Where you can get a standard 200x100 concrete block for around a tenner per square metre, clays are often start around 12 quid, although there are some 'bargains' out there, if you want to hunt around.

With clays being a 'natural' product that is kiln-fired, they have a more organic, less manufactured look than many concrete pavers, although the cheapest format remains the 2:1 ratio brick shape. Other formats are available, but you're going up the price scale if you move away from the standard format.

Follow some of the links given in the Clay Pavings section of the Links pages and you'll be able to get a few catalogues/brochures that will further bewilder you with choice. smile

 ruler
Forum Question Best paving for a driveway - Robert Nixon - 28 February 2002
Help please anyone been in my position? Up to today I had planned later this spring to get my drive enlarged to Total 45sq Metre, to enable my son who has returned home get his car and mine + 12ft Caravan of the street (basically a backward L shape 11M x 4.5M

Until today was convinced that Block paving 200mm x 100mmx 50/65mm, But my next door neighbour was having his concrete fence posts and panels fitted, By the contractor who I was recommended by my Nephew who is a garden Centre manager to do my drive and my neighbours now says York stone flags would make a better durable drive to my neighbour he needs his drive for similar purpose to mine,

Our land is mainly peat and moves with the seasons What advice could you give re cost durability etc

forum answer Tony McCormack - 28 February 2002
Hi,

structurally, there's nowt to choose between yorkstone paving and block paving for a residential driveway, assuming top quality materials are used. A properly laid yorkstone drive will give you at least 25 years of service, as will a properly laid block paved driveway.

Maintenance-wise, they are both similar in that they need cleaning and weeding once a year to keep them in prime condition, although you can minimise this wth the use of a quality sealant.

But cost-wise is another matter. Best quality reclaimed yorkstone will set you back around 35-40 quid per m² just to buy the flags, whereas you can have rectangular block paving completely installed for that sort of price, or a few quid more. New Yorkstone is even more pricey, but there are cheap imports now on the market at around 20-35 quid per m². There is, however, some concern about the quality of the real 'bargain' priced stone, though - see other threads.

Another consideration is that yorkstone is known to 'walk' overnight. Because it has such a good resale value, the drive bandits are always on the lookout for a nice yorkstone driveway that they can load onto their wagon while you're on holiday or away with the caravan. Block paving is much less likely to be stolen.

At the end of the day, it depends on your personal taste, your budget and what sort of property you have. In my opinion, there is no better paving for residential driveways than block paving. It's relatively cheap, it's easily maintained, it's attractive, it's easy to repair. There are indeed some properties where Yorkstone looks better, but for 9 drives out of 10, block paving is a better choice.

I wonder if this contractor is pushing you towards yorkstone because there's more profit in that for them than there is in block paving? Why not get them to price both options and we'll have a look at their specifications, if you wish.

 ruler
Forum Question Clay pavers to garage - Chris - 28 February 2002
|I have been asked to do a paving job that requires about 12m² of 50mm clay pavers to be laid in front of a garage. Two paving strips will run up to meet this area from the street. These strips provide plenty of room for an old M.G to be taken out on the occasional weekend. A builder has poured the concrete base for the strips and area at the front of the garage. My problem is that this new paving has to blend in with existing paving (60m²) which is all butt jointed herringbone pattern on crushed rock and sand. Can I screed a 20mm bed of sand /cement blend over the concrete base and lay the 50mm pavers on this, and then run a compacting plate over the top? I can't leave a gap between the pavers as this will not blend in with the existing paving.

Have you got any tips?

Thanks for a terrific site!

forum answer Tony McCormack - 28 February 2002
I'm glad you like the site, Chris!  smile

What you are proposing is to lay clay pavers as a rigid pavement to your two strips, and attempt to make it look not too dis-similar to the existing flexible paving. Normally, your methodology would be frowned upon, as rigid paving should really have mortared joints, but, for the scale of the job in hand, I think you might just get away with it.

The outer edges of the two strips need to be bedded on a class 1 mortar (assuming there is not enough depth for a concrete bed) and then haunched as per usual, leaving the inner 'body', which will be pretty narrow. I'd actually be tempted to lay these blocks on clean (ie, no cement) grit sand, but you could use a weak, semi-dry mix if you prefer, say 10:1, with *no added water*. Screed and lay the blocks as for flexible paving, and then compact with the wacker plate.

If you use a wet mortar to bed the blocks, the wacker plate will pump the mortar up and out via the joints, making a right bloody mess of the paving in the process. Using a semi-dry mix, or clean grit sand, and then brushing in jointing sand before compaction will help avoid that happening. The mortar-bedded and properly haunched edge courses will hold the paving in place, so they neeed to be laid at least 48 hours (at this time of year) before the wackering takes place.

Does that help?

 ruler
Forum Question Sand Coverage per Tonne - Dave Leishman
Hi
First I'd like to say what a great website - it's given me the confidence to plan and attempt block paving knowing that there's a good source of reference to fall back on! Keep up the good work!

I'm planning to block pave my driveway eventually, but I thought I'd start with the patio (20m²) and then garden paths first - where it's not quite so visible! I've noted the DTp1 coverage/tonne rates and prices that you quote but I can't find any for sharp sand. Can you give me an idea of the sort of coverage per tonne at 50mm compacted depth? Thanks...

forum answer Tony McCormack
Hi Dave,

the coverage rate for sand is given in the Pop-Up Calculator on the Screeding page, but you should find that, depending on moisture content, it's around 10m² per tonne at 50mm deep

 ruler
Forum Question Block Paving on a slope
I have a driveway which has a slope of approx 1 in 8. I am considering block paving over the existing concrete which is in good condition. I am wondering if this is feasible. If so could the 'flexible' method of construction be used (ie grit on top of the concrete) or would the blocks be better laid in mortar (rigid method).

How effective are block paving sealants in restricting moss growth etc in the joints?

Congratulations on a superb web site!

forum answer Tony McCormack
I assume you've read the notes on laying blocks over an existing concrete base, Roger. bearing in mind the comments about cutting out for thresholds, how much of the ex conc would remain?

This is one of those jobs that's best decided on a case-by-case basis. Flexible construction is by far the easiest method for DIY'ers, as rigid can be messy and time-consuming, and you have to use clay pavers. So, unless there's good reason, I'd go for flexible.

How feasible would it be to jack-hammer out all the existing concrete?

 ruler
Forum Question Dolomite for sub-base - Malcolm
Hi
I am getting some estimates for a block paved driveway along with our neighbour. She has had one quoting for dolomite for the sub base. I am not a builder but as far as I am aware this is something like crushed limestone. How does this compare to "DTp1" or "50mm Crusher run". Is it just another name used for the same material? Just want to get my facts right in advance.

This driveway will be replacing a tarmac drive which has been down since the house was built 12 years ago. Overall it is basically sound apart from a long crack running parallel from one edge and the surface is now getting pitted and grotty looking. Also, it appears to have settled down about 0.5" relative to a drain in the centre. From what I read, I belive it is possible to retain this sub base. This may be dolomite. When the house was being built I remember the site foreman talking about a delivery of the stuff for drives and pathways.

forum answer Tony McCormack
Hi Malcolm,

dolomite is just another rock type and should be fine as a sub-base material. It may actually be classed as a DTp1, depending on its source. Whereabouts are you? Most of the dolomite is found/used in the east and SE.

As for the existing sub-base, after 12 years it's probably settled as much as it is going to settle. A bit of re-grading to the top 25mm or so, and re-compacting should be all that's needed.

Malcolm Hi Tony
I am in the North East, Newcastle/Sunderland area. I've heard quite a few people talk about putting down the "Dolomite layer". So if the dolomite contains all sizes "down to dust", or I find out its the stuff they use on public roads, it could be DTp1 or as good as?
Tony McCormack I thought you might be somewhere around there, as the biggest source of dolomite is them hills near Middlesborough (I can't recall the name now!!)

It probably is a DTp1. At worst, it would be a DTp2, but it should be fine for your driveway. DTp1 is the stuff they use on public roads - it refers to a distribution of grain sizes and rock hardness, not to a specific rock type. So, f'rinstance, over here in the NW, we get a DTp1 that's gritsone from the Pennines, limestone from the Peak District, hardstone from N.Wales or even a granite shipped into Liverpool from some island they are quarrying of the W coast of Scotland. All very different rock types but all qualifying as a DTp1.

As long as there is the right balance of fines and lumps, it will be ideal.  smile

Malcolm Cleveland hills?

Thanks Tony. At least I won't tell a contractor his dolomite is rubbish, rather confirm that it has the right mix of sizes.

Just out of interest, what is DTp2? Is that the 50mm crusher run stuff?

Tony McCormack Cleveland Hills! That's 'em! It's a few years since I last had a trudge around those parts! smile

With regard to DTp2, it has a slightly different 'grading envelope' to DTp1. I can't find the spec just at the mo', but if memory serves me well, it has more 'dust' than DTp1. It's a minor diff, and not one that would make a masive difference to a residential driveway, but, seeing as it's the same price (to within pennies!) as DTp1, you might as well have the best stuff!

50mm crusher run is a very loose term that would probably be classed as a "Selected Fill Type 1 (SF1)". There's no grading envelope for 50mm C/run - it's all, more or less, passed through a 50mm sieve, so, theoretically, you can end up with all lumps or all fines, but, generally, it's a rough mix of lumps and fines.

Aren't you glad you asked! wink

 ruler
Forum Question Relaying pavers to improve drainage - Dianne
Hi, I am finishing off the job started 20 years ago by a former owner. The problem is that they laid the pavers with little if any drainage and they use a basket weave pattern where all bricks have a gap of half an inch separating them. I would like to know how I can:
1 - relay to improve drainage
2 - relay to remove the gap between the bricks

Has any one got some simple methods of achieving the task.

Thanks, Dianne

forum answer Tony McCormack
Hi Dianne,

assuming you can get your hands on extra bricks to complete the project, I would take the lot up and re-lay from scratch. You need to lay the pavers with a fall, so that they drain towards a gully or other drainage point, and I'm not too keen on the wide gap between adjacent pavers - they should be laid hand-tight to their neighbours with a gap not exceeding 6mm.

Lift the lot and set aside somewhere out of the way. Re-grade your bedding layer, adding fresh bedding sand if necessary, to create the requisite falls and crossfalls, and then re-lay your pavers. As you're eliminating a gap, you'll probably find yourself short of pavers, which is why I mentioned being able to get hold of extra stocks. If you can't get an exact match, you may be able to use the new bricks to create a soldier edging and then rely on the old bricks to pave the body of the pavement.

Does that help?

 ruler
Forum Question Laying block paving in wet conditions - David
Hello Tony,

We are having block paving laid on our driveway. The contractors have got as far as laying the sand and put some of the blocks in place. Then we have had about 2/3 weeks of rain, during which they have not been able to proceed.

My question is, how dry does the sand have to be before they can continue and finish the project? If the sand is damp, is there any danger of movement after the job has been finished?

Best regards

forum answer Tony McCormack
Hi

the sand has to have some moisture content, usually 3-10%, so it doesn't need to be bone dry before laying. A suitable grit sand will drain itself within an hour of the rain ceasing - if it's retaining water longer than that, then either it's the wrong type of sand or the sub-base isn't draining.

 ruler
Forum Question Marshalls Clay Cobbles - Brian Vickers
We have a patio laid with Marshals clay cobbles, which I will have to say looks good however it is presenting us with a number of problems all related to the size of gap that has to be filled by the sand. By the nature of the cobbles the gaps for the sand are quite wide

I was told by the contractor that these would quickly silt up and the sand become quite rigid. This is to a certain extent true, but it easily dislodged by roof overhangs, even garden furniture will concentrate the drips and erode the sand. It also makes a great home for ants that cause further damage. When I raised this as an issue with the contractor, he sealed the patio, which helped to a certain extent but by now has completely disappeared. How can I keep the sand in the gaps? (Apart from the aesthetics, the loose sand ends up in our nearby swimming pool)

The patio now needs cleaning, power washing is out of the question, even using a stiff broom will dislodge the sand and also the dirty water is going to satin the sand, any suggestions here.

Finally the cobbles adjoin concrete paving slab surrounded pool. The intention was at a later stage to extend the cobbles around the pool, they have now proved completely unsuitable for that, so I have a hard edge of nice Red clay cobbles lying against rather scruffy concrete paving slabs. It looks really ugly. The problem is compounded by the fact that the slabs. Any suggestions?.

Thanks for any help

forum answer Tony McCormack
The clay cobbles shouldn't really have exceptionally wide joints. I have them for my garden paths, and the vast majority of joints are 3mm or thereabouts. There are odd spots where the joints might be, say, 10mm, but these really are odd spots here and there, not what you might call extended joints.

The sand does seal itself, but even so, ants will still mine it, and rain or regular dripping will scour the surface. The only remedy is either to use a quality sealant or to use a joint stabilising liquid, such as the Keybond by Marshalls, or a polymeric jointing sand, such as GeoFix. I've not much faith in either when there's a lot of scour or dripping, so I always recommend a sealant in these situations.

I'm not too sure what you're driving at with your final paragraph. There seems to be half a sentence missing - can you clarify?

Brian Vickers Thanks for the prompt and useful reply.

Is there a particular sealant that you would recommend?. I have also heard of in the past an epoxy(?) and sand based jointing compound (Geofix seems to ring a bell) have you any experience of this?

Sorry about the last para what I meant to say was "Finally the cobbles adjoin concrete paving slab surrounded pool. The intention was at a later stage to extend the cobbles around the pool, they have now proved completely unsuitable for that, so I have a hard edge of nice Red clay cobbles lying against rather scruffy concrete paving slabs. It looks really ugly. The problem is compounded by the fact that the slabs are laid over reinforced concrete. Any suggestions would be gratefully received."

Tony McCormack I have a client on the outskirts of Liverpool who was recommended to use GeoFix on his cobbles by the previous contractor, and he's had nowt but trouble from the moment the cheque cleared. Whether it's because the prep and placement of the GeoFix wasn't done properly, or whether it was a bad batch, or even whether it was not genuine GeoFix (some naughty contractors 'dilute' it with extra sand), I cannot say for sure, but the lot is coming out next month and is being replaced.

As for extending the clay cobbles around the pool, I'd try out the sand joint with sealant - Resiblock will give you a free sample that you can try, enough for you to judge its effectiveness. As I say, try it out, and if that works (it should!!) then you could extend the clay cobbles all around as you originally proposed.

However, if you want other ideas, I'd need to see pics, so I have some idea of what we are dealing with. You can email jpgs to , if you wish.

Barry Wise words on the Geofix.

We've used it twice, and I will never use it again.

Within a couple of months, cracks appeared and the surface discoloured badly. Note that nobody could have followed the instructions more carefully than I did.

The stuff is useless - virtually zero adhesion, very little strength, allows water to filter into the base and discolours. I'm amazed they get away with selling it, as it doesn't do what it claims. It is also expensive.

Barry.

Tony MCormack I was speaking with Mr Geofix just before xmas and he told me he had done a deal to bring over the "Sandlock" product from the US. It's supposed to be better, but then, they would say that, wouldn't they!

He was to send me more info, but he never did, and I haven't seen or heard from him since. That's not really the best way to get your products used within the trade.

Does anyone[ have any success stories with Geofix?

John What size joints did you use Geofix in, Barry?

I have used Geofix before on various pavings but not on cobbles.

I find it excellent on joints at 6mm especially on coloured flags.quick and easy to use.

Feb (the manufacturers) sent me brochures on work that it has been used on upwards of 1500 and 2000m²

Maybe you had a bad batch Barry. Feb's literature states load strenghts for the product and it comes out seemingly stronger than mortar,

I can only go what they say it could be a sales pitch but it looks pretty impressive.

John

Tony McCormack I've taken some pics today of some desperately bad Geofix, used to joint around reclaimed setts. I'll be building them into a page at some point, but, having seen the mess it's made of what was a bloody expensive job, I'd be very reluctant to recommend it's use on any joints wider than 4-6mm.
John Hi Tony
I agree - I wouldnt use on any joint over 6mm. I wouldnt try it on Heritage or anything similar

John

 ruler
Forum Question Weight capacity - Len Bryant
What is the weight capacity of a standard block paved drive constructed by an approved contractor?

Does parking a single axle caravan, overall weight 1500Kg - hence 750Kg per wheel, on block paving require any special construction?

forum answer Tony McCormack
Hi Len,

it depends on how you define "approved". There is no official 'approved' status for block paving contractors, but some of us in the industry are trying to do something about that.

Anyway, assuming you have a 'standard' driveway laid by a reputable contractor using quality products, it can easily take the weight of a family car, a Tranny van or a caravan.

The strength of a driveway really depends on what the existing ground is like, but, assuming you're on anything half decent, a standard 100mm sub-base with a 35-50mm bedding layer and then a 50 or 60mm block should suffice for a caravan hard-standing

If you have any concerns about the existing ground, you could beef up the sub-base to 150mm and use a geo-membrane between the sub-grade and the sub-base layers.

 ruler
Forum Question Bills of Quantities - John at Aintree Paving
Hi Tony

In your Excel spreadsheet for pricing 30m² of block paving you estimate for 8 tonnes of MOT.

To get a compacted layer to 100mm do you not think 8 ton is excessive.Or do I read the spreadsheet wrong

John

forum answer Tony McCormack
Hi John,

Good to see you again. smile

8T may seem a lot at first glance, but here's the calculation in detail.

The density for DTp1 is 1.98 T/m³, so.....

30m² x 100mm = 3 m³ @ 1.98T/m³ = 5.94T

However, the calculation allows for spread around the perimeter of, IIRC, 500mm, so we have 22m of perimeter (5x6m = 5+6+5+6) which gives 11m² extra sub-base....

11m² x 100mm = 1.1 m³ @ 1.98 m²/T = 2.18T

hence, 5.94 + 2.18 = 8.12T

If you reduce or eliminate the spread, you save quite a bit of stone.

John Cheers Tony

Theres no catching you out, is there?

John

 ruler
Forum Question Old base material (can it be used) - Brian
I have plans to lay a block paving drive , I currently have a tarmac drive about 40 years old, exploratory digging shows that it has a base made up of what appeare to be old brick chippings. Can this be left in place or should it be removed? The tarmac seems to be splitting from it leaving a clean base.
forum answer Tony McCormack
Hi Brian,

I should think it will be fine. If it's been carrying that bitmac drive for 40-odd years, then there's absolutely no point in ripping it out and replacing it with something new. You know it's not going to settle or move - not after all this time!

You may have to re-grade it to accomodate the different levels of the block paving. Most old bitmac drives are 75mm thick, whereas you need around 100mm to accomodate the bedding and the blocks, so scraping off the top 25mm or so and re-compacting is a likely task.

Also, if there are any serious voids in the old sub-base, it's well worth getting in a couple of tonnes or so of extra bedding sand (coarse grit sand), scattering that over the surface and wackering it in to fill any holes before placing the bedding layer.

Hope it goes well for you - keep us informed of how you're doing.

 ruler
Forum Question Block paving on absolutely soaking clay - Barry
We are currently laying a small area (30 or so metres) of block paving in front of a shop.

Having dug out to 250mm, it had been our intention to follow our normal procedure of putting down a thin hardcore bed, 125mm of scalpings, 60mm of sand and then 60mm blocks. All, of course, compacted with the heaviest roller we have.

But, what with the weather of the last few weeks, the soil - a heavy clay - is absolutely saturated. The drive will be used for parking light vehicles (probably cars only).

Should we leave everything to dry out before putting down the sub-base, or am I worrying too much ? Does anybody have any other comments?

Thanks,
Barry.

forum answer Tony McCormack
Hi Barry,

sounds like a job that could use either a short length of land drain beneath the sub base or a drainage composite. I'd definitely consider using a geo-membrane, something like Terram 1000, as that will keep the sub-base separate from all that clay.

Skim off any sloppy clay/mud on the surface, get the geo-membrane down and the sub-base in as fast as poss before the rain returns. Once it's in and compacted, it will help prevent the sub-grade degrading any further and you should have no further trouble - touch chipboard! smile

Why 60mm of sand? Is that before you compact and screed it?

Barry Thanks for your help - it's very much appreciated.

I've ordered a roll of Terram 1000 from Sheffield Insulations down in Tonbridge (they do a "mini-roll" of 4.5m x 11m, which is fine for this job) and will throw it down as soon as I can.

Yes - that is the depth of my sand bed before compaction and screeding.

Thanks again,
Barry.

 ruler
Forum Question Tegula circle - John at Aintree Paving
I have been asked to lay a drivesett circle raised 3" above patio level.

I note the circle has a diameter of 2.5m.

In setting out the kerbs first I presume the back of the kerb (Marshalls kKS kerb) has to be 1.25m radius from the centre of the circle. Does this have to be exact all the way around the circle or will I have play in the circle.

When laying the last ring I do not want to squeeze any in or have to cut any.

Can I lay outer ring first around the kerbs first and work in? I have laid one of these before but it was on the flat and straightforward, not on a raised level.

Does this make sense

John

forum answer Tony McCormack
It's not a good idea to assume the Tegula circle will be exactly 2500mm dia, John. If you get all the joints at 4mm instead of 3mm, you can be 12mm out by the time you get to the outer ring.

This is how I'd do it....

Establish centre, then set kerbs on semi-dry mix at 1.3m radius (2600mm dia) and place haunching concrete to back, but don't compact solid.

Screed bedding layer for circle, allowing for fall from centre to edges (25mm is about right), then lay the circle starting with the centre stone monstrosity and work your way out. When you get to last ring of blocks, bed them on extra haunching concrete and push up the kerbs to suit, so that the backs of the kerbs are tight against the edge of the blocks, which should be approx 3mm higher.

Use a rubber mallet to knock down the outer ring blocks to the correct level, which will compact the haunching concrete at the same time, and then, when everything's in place, haunch the front of the kerbs to prevent them being kicked out, or lay more blocks.

Leave it for a couple of days before wackering, to give the concrete a chance to set.

 ruler
Forum Question Block paving a patio - Greg
Hi Tony,

I am planning to lay a block paved patio but have a few questions:

The surface will only be subject to fairly light loads (i.e. people, patio furniture but no cars) Is it still necessary to have a 100mm sub base and a 50mm bedding layer, or can one/both be reduced?

Also the soil is fairly clay-rich, but given the light loading is a geo-textile cover overkill?

Finally, the garden slopes very slightly away from the house, so I'll have to lay a concrete kerb base where the paving borders the lawn, but do I need to put such a base under the edges of the paving that butt up to the house wall?

Hope you can help,

Greg

p.s. Website is great!

forum answer Tony McCormack
Hi Greg,

yes - you still need a sub-base and a bedding layer, even though it's only a patio. If you have really firm and stable ground, you could get away with 75mm of sub-base, but any less than that isn't really a sub-base: it's just a fill layer, with no inherent strength.

The strength of a sub-base comes from having a minimum thickness, 75-100mm, of a certain mixture of stone and fines. It is the load bearing layer of the block pavement and it's a false economy to skimp. The biggest single cause of sunken paving is inadequate or missing sub-base.

You don't need a geo-membrane. They're handy on bad ground, but for a lightweight application such as this, they are, as you say, overkill.

And as for the bedding layer, you need enough to 'cushion' the blocks, enough to allow them to bed in, but not too much so that there's a risk of settlement. The minimum recommended thickness is 35mm, but that relies on your sub-base being accurate to not more than +/- 10mm.

It's not worth spoiling the ship for a ha'porth of tar. It's a lot easier to do a bit of extra digging, and use a few barrows of extra sub-base at this stage than face having to lift and relay next spring.

You don't absolutely need concrete under the blocks adjacent to the house. We do it that way so that, when we screed off using those blocks as a level guide, they won't be dislodged. The house wall will act as the restraining edge.

For your kerbs, though, they must be on concrete and haunched with same. If you're draining towards the kerb and hoping to allow surface water to find it's way through onto the garden, you may need to leave an open joint in the kerb line every 500mm or so.

How's that?

ruler

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