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Yippydadada 10-17-2011 12:48 PM

Supporting Concrete Slab from Underneath?
The previous homeowner of our house converted the two car garage into living space. As in most garages, the garage floor is set down inside the foundation walls (~14 inches) resulting in the typical walk down from the normal living space onto the garage floor. In order to wall off the two garage doors the previous owner seems to have built a pho-foundation wall directly on top of the existing garage slab (just in the area of the two garage doors). And in order to level out the new converted living space floor with the original living space floor, large floor trusses were hung from the front "foundation" wall (where the garage doors had been) and the back foundation wall to form the new living space floor. So basically a portion of the new living area floor is now supported by this pho-foundation wall (while the rest is supported by true foundation walls) on top of the garage slab. The problem is that due to settling and probably water erosion a large portion of the slab has nothing underneath it (I can take an 8 foot stick and freely swing in back and forth underneath the slab) including the two pho-foundation areas (that were the garage doors). There is no indication that the slab has actually moved and there are no cracks (but the portion that is supporting the wall and floor is completely floating somehow). My questions are, how big of a deal is this? What is the easiest way to fix this (I need this to be a DIY job)? The obvious answer is to hire someone to pump new cement underneath the entire slab. But as a DIY option is it possible to basically build a "foundation" wall (with concrete blocks and cement) underneath the supporting portion of the slab? Thanks

jcrack_corn 10-17-2011 02:04 PM




you probably need to have grout/cement pumped. there may be other soil issues and plumbing issues.

its not a DIY job...maybe a pho-DIY job.

which means you need a pro (not a pho-pro)

joed 10-17-2011 02:08 PM

Mike Holmes just fixed a basement floor with a special type of foam pumped under the hollow floor to fill the voids on the Holmes Inspection I watched.

Ron6519 10-17-2011 03:44 PM


Originally Posted by joed (Post 750631)
Mike Holmes just fixed a basement floor with a special type of foam pumped under the hollow floor to fill the voids on the Holmes Inspection I watched.

Was it real foam or pho phoam?

woodworkbykirk 10-17-2011 05:25 PM

dont believe everything you see on tv... the big thing to realize with holmes is that hes working with an unlimited budget for a few reasons, he has all kinda of corporate backing and he gets to use quite a few new products that arent that well known about because these companys are donating their product to give it more exposure

stadry 10-18-2011 04:24 AM

would venture a guess you have the traditional 2 chances of doing this as a diy project,,, will even bet holmes didn't do the actual work but subb'd it out,,, understand there are some foams being used for structural supportive sub-sealing but we still prefer our own methods - grout, soil grouting, & expansive sub-sealing - these aren't diy jobs - 1st, no one rents the necessary equipment & 2nd, experience / expertise doesn't come on a cd :no:

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