Reallu necessary for hardcore under concrete for paving?

replaylite

Hi,

I am laying a concrete slab for paving flags soon. I am considering laying 4 inches of just concrete on fairly compacted soil. What do you boardsies think is it a bad idea. Do I really need something like sand or gravel under it or is it fine the way it is?

There won't be any great amount of weight and there will be paving flags on top so smal cracks wont be that visible

Xcellor

Soil tends to move with rain / cold / heat. Just because its compacted now ands seems firm does not necessarily mean its good enough to support heavy concrete. Personally I would put some hard core of some description... I mean any old rubble etc will suffice.

Of course you can risk it. Perhaps it won't make a difference in your case.

antiskeptic

replaylite wrote: »

Hi,

I am laying a concrete slab for paving flags soon. I am considering laying 4 inches of just concrete on fairly compacted soil. What do you boardsies think is it a bad idea. Do I really need something like sand or gravel under it or is it fine the way it is?

There won't be any great amount of weight and there will be paving flags on top so smal cracks wont be that visible

Nip along to chadwicks and buy yourself some steel reinforcing mesh. After cutting it to suit the shape of your path (allowing for a 4" overlap where sections of mesh meet) simply press it down into your slab when poured. Let the mesh rest an inch or so from the bottom (with perhaps a wooden block here and there laid under the mesh to stop it sinking completely to the bottom) and your slab will be fine

Messy but effective.

Martron

dont buy mesh...... in fact skip the concrete slab altogether and just put down the 804 and then a layer of sand then your flags.

replaylite

I don' plan to go with the sand as I will likely be excavating around the path at a later point and if I use sand the slabs will move so It will have to be concrete I'm afraid!

Martron

The 804 ( hardcore ) will provide your base.

the sand is used to blind the 804 and give you a layer of softer material(50mm or so) so you can level your slabs better.

if you dig around the slab you risk underming it anyway . its easier to recompact stone rather than backfilling under a slab.

gsxr1

concrete is not used for laying flags. It is usually dug up for flags.

804. sand, wacker and a level. yur only man

As yur man Martron said

dunsandin

tis if you want em to stay layed.