hi all great site.
i am about to start laying bradstone carpet stones on my driveway.in the bradstone brochure it states you have to have a concrete base of between 100-150mm,then a bed of sharp sand/cement mix 40mm deep ,under the carpet stones.im going to cover an area of 60m2.
i was wondering if i could get away with laying 100mm of type1,vibrate it down,then the sand/cement mix 40mm on top of that.i dont know why they want a concrete base ,when i dont think you need it for monoblock.can anyone advice
laying carpet stones
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84-1093879891
The reason why the folk at Bradstone recommend laying the Carpet Stones on a concrete base is the old "stiff on stiff" rule of thumb, ie, if you're using a stiff bedding, which would be the case with a sand/cement bed and mortared joints, then the base should be stiff, also. The thinking is that, if you use a rigid bed/jointing on a flexible sub-base, then any slight movement in the sub-base will result in cracking of the bedding/jointing.
Monoblock, or block paving as it's called south of Hadrian's Wall, is a flexinble paving. The bedding and the jointing are unbound, that is, no cement, and so the blocks can be laid on a standard sub-base.
The problem with the Carpet Stones is the joint width - they're too wide to rely on an unbound jointing material, such as sand, so you're more or less obliged to use a mortar (or a polymeric sand), which, because of the small unit size of the individual "stones" means that a bound bedding is required, which, in turn, requires a bound base. However, you could get around this on a patio with foot traffic only be laying the Carpet Stones onto a 75-100mm thick bed of concrete laid over a sub-base. That would be strong enough to take pedestrians in low numbers, but would not be suitable for a driveway, such as you have, where the only sensible option is to use at least 100mm of concrete as a bed/base, or, as it says in the brochure, lay a concrete base and rely on a 20-30mm layer of mortar to bed the damned things.
Monoblock, or block paving as it's called south of Hadrian's Wall, is a flexinble paving. The bedding and the jointing are unbound, that is, no cement, and so the blocks can be laid on a standard sub-base.
The problem with the Carpet Stones is the joint width - they're too wide to rely on an unbound jointing material, such as sand, so you're more or less obliged to use a mortar (or a polymeric sand), which, because of the small unit size of the individual "stones" means that a bound bedding is required, which, in turn, requires a bound base. However, you could get around this on a patio with foot traffic only be laying the Carpet Stones onto a 75-100mm thick bed of concrete laid over a sub-base. That would be strong enough to take pedestrians in low numbers, but would not be suitable for a driveway, such as you have, where the only sensible option is to use at least 100mm of concrete as a bed/base, or, as it says in the brochure, lay a concrete base and rely on a 20-30mm layer of mortar to bed the damned things.
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102-1093880258
thanks for the advice.
the bedding mixture for these carpet stones is 6 sharp sand to 1 cement,does this mixture still thoroughly harden.when the stones are laid,i am suppsed to brush in a mix of 1 part cement with 3 parts sharp sand.i was under the impression that the mix wouldnt harden thoroughly and would be slightly flexible.
i know laying concrete is the correct way,but the last thing i want is the expense and labour of laying it.is there no mix i could use on these stones that would give me the flexibity required.
the bedding mixture for these carpet stones is 6 sharp sand to 1 cement,does this mixture still thoroughly harden.when the stones are laid,i am suppsed to brush in a mix of 1 part cement with 3 parts sharp sand.i was under the impression that the mix wouldnt harden thoroughly and would be slightly flexible.
i know laying concrete is the correct way,but the last thing i want is the expense and labour of laying it.is there no mix i could use on these stones that would give me the flexibity required.
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84-1093879891
You've lost me there! There are no cement-bound products that are flexible - it's just not possible. Cement is a hard, non-plastic material when cured, and so it can never be flexible, at least, not at the sort of joint width we're considering!
A 6:1 bedding layer will be reasonably hard, somewhere around 15-20 Newtons, I'd estimate, and a 3:1 jointing mix would be even harder/more brittle, at around 30-40 Newtons, so your plan to use a flexible jointing material is a non-starter with any cement-based material. What made you think that a cement-based material would be flexible?
I can't understand why you would want a flexible jointing material, anyway, when you're laying on a rigid bed. Remember what I said in my previous post - "Stiff on Stiff" - if you use a stiff bed, then you should have a stiff joint. If you really want a flexible joint, then you need to look at a bitumen-based sealant, or some other elastomeric compound, such as Nitoseal, but the cost would be astronomical. A rough calculation tells me it would cost more for the Nitoseal to fill the joints of a single mat of Carpet Stones than it would for the mat itself!
Why not contact Bradstone and ask what they suggest? I bet they have only one option, the one in the brochure!
A 6:1 bedding layer will be reasonably hard, somewhere around 15-20 Newtons, I'd estimate, and a 3:1 jointing mix would be even harder/more brittle, at around 30-40 Newtons, so your plan to use a flexible jointing material is a non-starter with any cement-based material. What made you think that a cement-based material would be flexible?
I can't understand why you would want a flexible jointing material, anyway, when you're laying on a rigid bed. Remember what I said in my previous post - "Stiff on Stiff" - if you use a stiff bed, then you should have a stiff joint. If you really want a flexible joint, then you need to look at a bitumen-based sealant, or some other elastomeric compound, such as Nitoseal, but the cost would be astronomical. A rough calculation tells me it would cost more for the Nitoseal to fill the joints of a single mat of Carpet Stones than it would for the mat itself!
Why not contact Bradstone and ask what they suggest? I bet they have only one option, the one in the brochure!
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102-1093880258
contacted bradstone,they said i probably could get away with type 1 as a base,so i tried it and hey presto, it worked,no movement at all.i managed to get a hold of a flexible mortar substance called polymartic.managed to get it from a local builders merchants.its a new product from canada.its like a mortar like susbstance with a pernament plasticiser bound in it.you can dye it the colour of the carpet stones.it great as in its gives lots of movement of the stones,a bit like chewin gum.
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nev
- Posts: 3
- Joined: Mon Jun 02, 2003 9:23 pm
Why would you want your bradstones to move around?
I missed something here anyway, what I want to know is reading this post gave me an idea, I have a concrete drive a bit uneven in places with a join here and there and the odd crack, I assumed I would have to have it all dug up and start again for any improvment to the driveway, but after reading the posts on this topic I wondered, do you think I could lay carpetstones or something similar on the top of my concrete drive?. what you think.
Cheers Nev
I missed something here anyway, what I want to know is reading this post gave me an idea, I have a concrete drive a bit uneven in places with a join here and there and the odd crack, I assumed I would have to have it all dug up and start again for any improvment to the driveway, but after reading the posts on this topic I wondered, do you think I could lay carpetstones or something similar on the top of my concrete drive?. what you think.
Cheers Nev
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84-1093879891
In response to fras - you may think there's no movement of your carpet stones on a DTp1 bed, but there is! It may be minimal, but they will be moving - that's the natuire of the best with an unbound bed.
I'm not sure about this Polymartic stuff. It can't be a flexible mortar, and my guess is that it's just another polymeric sand. You say it contains a "permanent plasticiser", but that doesn't make any sense, as a plasticiser keeps mortar plastic, ie, workable, unset. I'll have to see if I can find out anything about it.
To Nev - have a read of the Paving over an existing base page to see if your idea is feasible.
I'm not sure about this Polymartic stuff. It can't be a flexible mortar, and my guess is that it's just another polymeric sand. You say it contains a "permanent plasticiser", but that doesn't make any sense, as a plasticiser keeps mortar plastic, ie, workable, unset. I'll have to see if I can find out anything about it.
To Nev - have a read of the Paving over an existing base page to see if your idea is feasible.