I am about to get my driveway full slabbed using normal concrete slabs like below (i will be using rectangle slabs as opposed to square).


The builders that came to give me an estimate said it would be best if cement was placed under the slabs so they stay together. I was just wondering if this was common practice? Is it better to have concrete as opposed to just sand or even soil?

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    (BTW, cement is not the same as concrete...) I'd be worried that the slabs would tip relative to each other, so the drive would get more and more bumpy. Concrete would support the joints so that they'd stay flush. – Daniel Griscom Apr 28 '16 at 15:38
  • Why would you pay to have a concrete slab poured, then cover it with concrete tiles? – isherwood Apr 28 '16 at 15:51
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    Aside from mechanical issues, one thing you need to be concerned with is that, unless you pour concrete under these blocks, within a few years you will have aggressive weeds growing through every gap between blocks. If it were only a walkway, packing gaps with mortar might have mitigated the problem (though not solved it completely), but, with vehicle traffic, I don't think that mortar joints would hold up for long. – Eugene Smith Apr 28 '16 at 18:11
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    That's not going to do anything. Individual pads under your slabs won't be any more stable than the slabs themselves. A properly-prepared sand/gravel base is the right solution. – isherwood Apr 28 '16 at 18:24
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    You like this look, or you already have tiles on hand? If you just like the look, go with stamped concrete; notice how at least two of those tiles are cracked. Movement isn't as much as a concern as the substrate being able to support them. – Mazura Apr 28 '16 at 18:26

You do not want to just place the concrete tiles on native ground soil. A proper installation would be to dig out the native soil down to a solid base. Then lay in a layer of crushed rock to aid in water drainage. Directly under the concrete tiles would be some sand that makes it possible to level and even out the tile installation.

With the correct materials that are properly packed in and if the water drainage from the area is implemented correctly an installation should stand up well without adding concrete under the tiles. But keep in mind that they will move around if there is winter frost action, an unstable base soil, very large vehicles driving over them or if there is a regular flow of water over and between the tiles down into the base materials. This movement can be mitigated by placing concrete under the tiles but there is a tendency to make this layer fairly thin and this can still crack and allow tile movements.

My recommendation, if you want a driveway that will stand up to these stresses, would be to not use these tiles at all. Instead put down the crushed rock base and sand as a base. Then place in heavy duty wire mesh AND rebar in both directions in a manner that it ends up in the concrete as opposed to laying on the sand. Pour concrete to a good thickness (using 2x6 forms is far better than using 2x4 forms). Once the concrete is poured and being finished there are any number of techniques that can be used to make it look less like a slab. The simplest would be to surface groove it to look similar to the tiles. Other techniques include embedding brick borders, pebble surface finish, or even brick like patterning rolled into the surface. The latter is often done with the concrete dyed a reddish color.

  • Stamped concrete, plus one. – Mazura Apr 28 '16 at 18:26

Both sand and soil will not hold up long as water flows through the cracks the slabs will sink when driven over. At a minimum 3-4" of crushed quarry rock heavy compacted. Concrete under the edges to tie them together would be much better at least 2" thick in my opinion.

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