# Sub Base for pavers



## mcgyverdc

I've got a job of 4500/ft2 pavers to do but have a question about the sub base. Whole job will be on 100 ft deep sand base! In other words there is no hard sub base to excavate down to. the sand is very well compacted and undistrubed, damn near an early sandstone feel. it has a gravel driveway on it now and the stone has not disappeared over the past 10-15 years so i'm thinking it should be suitable to support the pavers. BTW drainage is not a problem! I'm thinking of just doing a 1" sand base over the existing sub and laying the pavers. Geo textile between? I don't usually use it but am thinking it may be necessary in this instance. Ideas? thanks


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## Teetorbilt

I'm watching as I have a personal project going, a circular driveway + some walkways. I live on an ancient sand dune.

I see dessicated granite spec.ed frequently but nobody around here seems to know what it is. My current thought is to tamp in about 4" of dry concrete w/wire as a base.


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## Tscarborough

Sand is fine, but it can wash, so make sure you have excellent edge restraints. Teetor, do not under any circumstances use stabilized soil/sand under pavers, it will cause them to fail. Pavers are a flexible pavement and require a flexible base.


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## Teetorbilt

Ts, the exsisting sand is not stable enough and pavers tend to move around. I was thinking of a layer of sand on top of the concrete base, the base is just to disperse the pressure.


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## Tscarborough

You would do better (and cheaper) with a 4-8" layer of road base/crusher run/crushed limestone. Extend it out wider than the driveway 6 inches or so and just a small amount past the edges on the sidewalks, and be sure your restraint is excellent.


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## tgeb

I would agree with Tscarborough. :thumbsup: 

Only I would add geotextile fabric below the stone base to add even more stability.

What part of the country or world are we talking here mcgyver?


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## Teetorbilt

Like #2 road rock? Your recommendation for 'restraint' ?????

I'm thinking a wall 12" deep X 4" wide of reinforced concrete. I only want to do this once.


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## Tscarborough

Segmental concrete pavers work a little (OK, a lot) different than traditional (american) pavements.

Think of a railroad track, not a highway. What you have, basically, is a surface that is interlocked in shear and tension floating upon a flexible base. The idea is to maintain that tension. This is why you need a flexible (though stable) base, and capable edge restraints. Concrete edging is a poor choice for the same reason that an inflexible base is. Under live loads, there will be deflection, and using an inflexible base/edge restraint will turn that deflection into deformation and lead to failure of the surface.

My prefered edging is Paverlock. It has been tested, both by labs and by me, and it works. For your application, I would halve the recommended stake-point distance, and sleep well at night.

The specific name and type of stone for the base rock is different in every part of the country, but it should consist of stone no larger than 3/4", with a consistent mix of gradation down to dust. This allows it to compact to over 90% and still maintain flexibility. The recommmended depth is generally 18" in normal soils, but sand is actually a pretty good base, since it will pack and still drain well.


Remember that this method is still relatively new in the US, but has been used for literally thousands of years in other parts of the world, with some of those thousand+ year old pavements still in daily use.


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## tkle

It's the base that needs to be restrained.Sand flows like water.I put old carpet 4"'s under mine with sand on top.Not something I would try on a customers house,but for my side patio it's holding up well.


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## mcgyverdc

Sorry all, It's in the Northwest, not very worried about frostheaval, very rare. I'm more worried about traffic causing "grooved " regions down the road. i'm sure that the subbase is undisturbed and solid but worried that the watter may cause some settling. Anyone see any problem putting geotextile just under the 1" sand setting base? Would provide some torsional rigidity and prevent the possible contamination of the sand under the geotextile....or do i even need to worry about it. Drainage is definitley not a problem. thanks


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## denick

Just some thoughts on your work question. 

In the work we have done over the years here in the New England area we have found that it is the uniform depth and consistency of the sub bases bearing capacity is what makes or a long life. 

If you have sand everywhere and you level it and compact it, can you go out there with a 4x4 and slam it down on the surface and it sinks into the sand the same depth in all areas? If yes you have a uniform capacity. If not you need to achieve that. 

Here we worry about frost heaving our work in an un uniform way. Yes, it all heaves sometime. As important, is that it relaxes back to the same height uniformly in the spring it has to go up and back down evenly across the work. You don't have that concern but won't sand be at its most unstable when it is saturated and when very dry. You say you don't have a drainage problem. Could you? in the wettest time of year? I would be most concerned about a very dry spell. 
I have never been able to walk on dry sand without it moving freely.

All this said if I were going to do your job and wanted a job with a long life. 
I would follow Tscarborough's advice, 
"The specific name and type of stone for the base rock is different in every part of the country, but it should consist of stone no larger than 3/4", with a consistent mix of gradation down to dust. This allows it to compact to over 90% and still maintain flexibility."

That base material, at least 4" thick when compacted. A stabilization fabric wouldn't be bad but use a real stabilization fabric.


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## mcgyverdc

Thanks, so would you say that a fabric under the 1" paver setting sand, after compaction of the subbase, would help? or no change as long as the edge resraints are very good? Going to finish up my quote tonight and not have to include a lot of excavation which will make them happy. thanks all


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## denick

1" of sand on top of fabric might cause more problems than it's possible advantage.


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## Teetorbilt

I'm getting confused and I'm pretty good at understanding these kinds of problems. Perhaps we should consider the definition of 'sand'. I have many types at my disposal. Very old beach, we call 'sugar sand', it is very fine and akin to glass beads or teeny ball bearings. Old beach is fossilized shell, can run from coarse to fairly fine with rounded edges. Recent beach is fairly fine but still relatively sharp on the edges.

I'll follow up with some pics of what the yard guys have done to a brick pathway that was installed by THE PREVIOUS OWNER. As soon as I can find the camera.


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## Tscarborough

Sugar sand is not a good base for anything. We can get into sieves, but it is not really so critical. Sharp sand is what I consider to be a good base, and is what should be used for leveling and for filling pavers.

In my experience, geotextile is not good under flexible pavements, but it really depends upon which one is used. If you use a product that is intended for use behind a retaining wall as an example, it will provide the torsional strength while not creating a weakness plane in the substrate like a woven or non-woven geotextile will.


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## Tscarborough

Let me also add that my criteria for sidewalks and patios are not even close to what I require for driveways or commercial use.


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## Teetorbilt

Ts, there is only so much that can be accomplished on the web. I am going to go see how it is done here. I see good jobs and bad, I know where to go. Sitting here was the easiest, no offense.


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## Tscarborough

Yep, but I can tell you this about that area, having done one project there at my parents house 200 yards off the beach in Lauderdale:

The sand is fine as it is. Restrain the edges and use a good sub-base and you are GTG.


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## mcgyverdc

Done! will skim off the 2-3" of gravel, compact and level, 1" of sand and lay the pavers, sweep in sand and compact again. forget the fabric thanks


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## xcavator

yes there are companys now recommending sand under thier pavers.


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## ckc

I did a 1500 sq ft paver drive in Ocean city NJ on the beach last year and gug 12" of sand out, wet/compacted, laid fabric, 8" of modified 2A stone, 1/2" sand, then pavers. No movement. I gaurentee work for five years.
I was nervous because I never did a driveway job in a sandy area, I'm from Philly (high clay subsoil). Spke to allot of Jersey guys and they said I'm ok with laying on existing sand..... sorry, did not feel comfortable. Stuck with what I was used to doing.

just my 2 cents


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