slab on grade - Contractor Talk - Professional Construction and Remodeling Forum

mjaafreh2008 · 02-15-2009, 01:26 PM

hi evry one , i was wondering what is the need of the base course layer which need to be excuted under the slab on grade , and if i used a single size crushed stone instead of nutural filling material , is it right to use base course on top of it ,,,?

neolitic · 02-15-2009, 01:40 PM

Quote:

Originally Posted by mjaafreh2008

hi evry one , i was wondering what is the need of the base course layer which need to be excuted under the slab on grade , and if i used a single size crushed stone instead of nutural filling material , is it right to use base course on top of it ,,,?

Around here pea gravel would be
the most common fill under a
residential slab.
Don' know what is available,
where ever you are.

AutumnWood Inc. · 02-16-2009, 12:13 AM

A Civil engineer needs to know what to use for a base material/slab....

and there trade is building....

skyhook · 02-16-2009, 12:41 AM

Quote:

Originally Posted by mjaafreh2008

hi evry one , i was wondering what is the need of the base course layer which need to be excuted under the slab on grade , and if i used a single size crushed stone instead of nutural filling material , is it right to use base course on top of it ,,,?

Pea gravel or aggregate would give the slab a cushion to move on in the event of an earthquake and also give the concrete a more uniform substrate to make it stronger. Separating the slab from highly expansive soil such as clay.

strightclaw · 02-16-2009, 01:15 PM

Generally speaking anything from Sand to # 57 stone is used under the Slab as a Vapor Barrier this is almost always covered with plastic something like 4mill ploy.If your outside such as a sidewalk or driveway no need for this just set the grade an go to it.

D.A.S.Anthony · 02-16-2009, 01:23 PM

Quote:

Originally Posted by mjaafreh2008

hi evry one , i was wondering what is the need of the base course layer which need to be excuted under the slab on grade , and if i used a single size crushed stone instead of nutural filling material , is it right to use base course on top of it ,,,?

If you truly are in the middle east I haen't a clue what to use. I can't even begin to imagine the unsetttling sand or earth that you are trying to build on over there.

thom · 02-16-2009, 01:34 PM

Here in Albuquerque almost all homes are slab-on-grade.

We are in a desert, there is little organic matter in the soil, and things are very dry.

We grade, tamp, and pour. Generally, if fill is needed, local fill is just fine. We don't install vapor barriers.

skyhook · 02-16-2009, 01:45 PM

Minimum vapor barrier in SoCal is 6 mil.

72chevy4x4 · 02-16-2009, 07:12 PM

question about vapor barrier in basement pours, what's the likelyhood the plastic will get torn during the pour-either with tools, rebar or by puncturing it on the stone (probably not if you're using pea gravel)?

Has anyone ever tamped the gravel then laid foam board down, then poured concrete for a basement floor? It would make a thermal barrier, but not sure about the gravel to foam board being a good surface to pour upon.

Chris Johnson · 02-16-2009, 07:38 PM

Quote:

Originally Posted by skyhook

Minimum vapor barrier in SoCal is 6 mil.

We just did one and engineer spec'd Stego-Wrap 15 mil.

SLSTech · 02-16-2009, 08:35 PM

Quote:

Originally Posted by 72chevy4x4

question about vapor barrier in basement pours, what's the likelyhood the plastic will get torn during the pour-either with tools, rebar or by puncturing it on the stone (probably not if you're using pea gravel)?

Has anyone ever tamped the gravel then laid foam board down, then poured concrete for a basement floor? It would make a thermal barrier, but not sure about the gravel to foam board being a good surface to pour upon.

About a 100% - go vapor barrier / plastic, taped, then foam board