For a 30x40 carolina carport enclosed building. This is not red iron building and is relatively “lightweight”. It doesnt require footings.

I am planning to do a 6in concrete slab w/wiremesh.

So today I got 2 estimates to do the dirt work/pad. One of the guys said he would just take out the top 8 inches of existing dirt and backfill and build up with red clay.

The 2nd guy said that a foundation requires digging out much more dirt than that (about 24-36 inches) and backfilling and building up with clay.

Looking for other opinions on the correct path I should go. I want it done right of course, but there is a several thousand $$ difference in the quotes.

Baton Rouge area.

This post was edited on 11/4/21 at 11:27 pm

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Posted by LSUtigerME

Walker, LA

Member since Oct 2012

3794 posts

Posted on 11/5/21 at 6:35 am to JAMAC2001

It really depends on the condition of the existing soil. Either could be correct, or it could require them to muck out even deeper.

In most cases, they will just need to scrape the top soil 6-8”, but on occasion it will require more.

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Posted by JusTrollin

Member since Oct 2016

230 posts

Posted on 11/5/21 at 7:57 am to JAMAC2001

1. If you want it done "right" hire a geotechnical company to perform an analysis and do a report.
2. Standard wire mesh is worthless, either use highway mesh or #4 rebar 12-24" OC depending on what you are using it for.

Where in BR, ground ranges from gumbo to stiff clay depending on location...

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Posted by rjo_lsu

Lafayette, La

Member since Jul 2005

396 posts

Posted on 11/6/21 at 1:12 pm to JAMAC2001

Unfortunately more often than not, getting it done right costs. I highly recommend to add grade beams to stiffen your concrete up. 6ga wire mesh is secondary reinforcement. Use either post-tension foundation system, highway mesh or rebar in top of slab.

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Posted by AUCE05

Member since Dec 2009

42559 posts

Posted on 11/8/21 at 8:38 pm to JAMAC2001

Clay will crack your slab. You need a drainage layer such as stone, GAB, etc How much material they remove will depend on site conditions. You need to remove all topsoil and unsuitable material. Compact the surface receiving your stone with the correct equipment (vibratory smooth drum for sand, kneading for clay). A soils lab can tell you what kind of dirt you have. If you don't hire one, look up the soil map for your property. Whatever you do, don't place concrete directly on clay.

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Posted by diat150

Louisiana

Member since Jun 2005

43514 posts

Posted on 11/9/21 at 6:16 pm to JAMAC2001

Did my own on a 30x30. Pretty much just scraped the top layer of dirt and grass and did a small footing around the outer edges. Backfilled with a little sand. Dont remember if we did 4 or 6 inch, i can look tomorrow. Used wire and I think we did 2-3 expansion joints. Not a single crack besides the expansion joint and its been over 10 years.

Only thing i would have done different is put 1/2 rebar along the outer edges to mount the beams instead of letting them use the bullshite they use.

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