DIY Home Improvement, Remodeling & Repair Forum > DIY Home Improvement > Bricks, Masonry and Concrete > Flooring over sloping concrete slab

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Old 07-24-2012, 03:49 PM  
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Default Flooring over sloping concrete slab

I need to level a concrete carport slab that is attached to the house's main foundation and is 5 1/2" below it. The 20' x 24' slab is 4" thick with perimeter footing under it and drops 1.375" over the 24'. The carport was never added and the existing slab has been used as a patio area. I hope to level out the 1.375"
drop with some type of concrete leveling compound and use a good portion of slab area to build a storage and shop area. The slab is at grade level and I was thinking of using treated 2x6 floor joists to raise the floor level up to that of the main house. However, sealing off water seepage between the slab and perimeter joists might be difficult. Maybe a 4" thick concrete perimeter wall 5 1/2" high with venting would be better. Anyone have any thoughts on the best way to accomplish this level flooring problem ? I've also read that some of the leveling compounds are not recommended for a thickness greater than 1". Trying to shim all the joists to level to doesn't seem practical either.

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Old 07-24-2012, 04:30 PM  
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Is mud jacking the slab an option. Maybe not a slab that large but, it could be cut into managable sections.
Or build the base of the new building to accomodate the slope of the slab so that from the sill plate up will be level.

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Old 07-24-2012, 05:34 PM  
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The slab was slightly sloped for water runoff. It has now well settled on two feet of select fill base and raising it even a couple of inches would be problematic and expensive. Getting the sill plate up to level (and even with the house foundation) is what my post was all about. The foundation base ( 2x6 joists) setting on a leveled slab surface was one possible approach. Pre-cutting each joists to accommodate the slope might be another. Shimming each joist every 3 feet might work also. So, what is the best way to build a level foundaton base ?
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Old 07-24-2012, 06:05 PM  
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We had a great discussion about this about a year ago, in this picture see while the foundation will continue under the gararge door but it dosn't continue to full height. So the floor can move up and down with moisture and frost.
Since that time we did just what you are doing. The city wanted the floor removed for crawl space to be dug out and foundation brought up to height. Or we could have an engineer design it.
He had us scribe treated 2x6 so they sat level and set them on treated 1x4 blocks every 16" this was to allow air flow under the structure. The 2x6 across the door opening was also held 3/4" off the concrete.
instead of building the front wall on top of the deck like normal he had us
nail studs to the side of the floor joists and keep them away from the concrete 1 1/2". That way if the floor moved those nails would let go before it lifted the front of the garage.

Last edited by nealtw; 07-24-2012 at 06:27 PM.
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