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Garage Slab Height

rom12398's picture

Question relating to location/depth of garage floor slab in home renovation I'm having done for my house:


Conctrator poured footers/foundations for the entire house, including garage. Contractor then framed out entire house, including garage, leaving cutouts for garage doors. They poured the garage slab after framing was complete. They poured the slab above the foundation, so that the edges of the slab sit ~4" up the framing wall (they put some sort of vapor/moisture barrier to contain the conrete keeping it out of the walls). I was originally concerned with this from an aesthetic viewpoint, being that our driveway will have to be raised from below foundation to 4" above foundation at the openings, but have becoming more concerned that this install is wrong from the getgo and may cause bigger problems down the road. 

Thoughts? Thanks in advance. 


WTF? (post #216194, reply #1 of 9)

I've never see nor heard of what you describe. I can think of a lot of reasons why it is wrong, but no good reason for doing it this way. What's on the plans? Pictures?

In picture, siding comes down (post #216194, reply #3 of 9)

In picture, siding comes down to roughly bottom of sill plate, you can see how garage entrance/slab sits ~4-5" above that. Plans look correct, don't know why actual is different than original. Am seeing contractor today will see how they respond. 

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Foundation height should be (post #216194, reply #4 of 9)

Foundation height should be at least 6" above finish grade, except at the garage. 

At the garage, top of foundation is stepped down below finish grade to allow for thickness of garage floor. 

Sill plate and siding at grade level is wrong.  Invitation for major moisture issues.

What is the foundation height on the rest of the house?

The level of the siding (post #216194, reply #5 of 9)

The level of the siding doesnt show the level of the foundation.  You would need pictures from the insdie to show the slab in relation to the wall framing.  The siding can be raised or lowered if need.

From the drawings... (post #216194, reply #6 of 9)

...... the slab should have been on top of the footings and the walls on top of the slab. I always pour the slab at the same time as the footings. What was done is not acceptable. Good luck. Fixing it now is a [CUTE LITTLE PUPPY].

Placing the walls on top of (post #216194, reply #8 of 9)

Placing the walls on top of the slab is certainly not the only appropriate way to build garage walls and it likely isnt even the most common way.

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I've never seen it done that (post #216194, reply #2 of 9)

I've never seen it done that way but I've only been at it 50 years. It sounds really stupid to me. So now your bottom plates  sit below the slab?  Sounds like nothing but trouble to me. I wouldn't pay for it, I'd fire the contractor and fine one that knew what they were doing.

Florida Licensed Building Contractor, 50 years experience in commercial remodeling, new homes, home remodeling and repairs and all types building maintenance.

Rot (post #216194, reply #7 of 9)

Every wood framed wall I've ever encountered that had concrete poured above the bottom plate had rot problems.  The walls need to be ont op of the concrete, not the concrete poured into and around them. 

You're trying to fix problems, not create them like this will do.  Reject it and tell the GC now so they can get moving on a fix.  

an't imagine why anyone would (post #216194, reply #9 of 9)

an't imagine why anyone would do that!  Hose out your garage and let the water flow over the edge of the garage floor and DOWN into your wood wall.  WOW.

And how is anyone supposed to pour your driveway even with the garage floor and not BURY your siding!!!!!!!

The builder appears to have followed the MORONIC plan as drawn, but should ahve stopped everything and questioned why the drawing was drawn that way.

Where did the drawing come from?