Looking for some expert advice …
About to begin a rebuild of a waterfront home. Tearing down existing structure to the slab (on grade), enlarging footprint on 3 sides of the slab.
Rather than just pouring the new slab areas for the additions, we plan to cut a trench in the existing slab (for plumbing/septic drains), and then pour 4″ on top of the existing slab. We need the extra 4″ of elevation because of zoning/flood management rules in the waterfront area. So, we’ll end up with an 8″ slab where we have poured over the old, and new 4″ slab areas for the additions.
The existing slab is about 40 years old. No settlement cracking in any walls, no telegraphing of cracks in flooring. Slab seems to be in excellent shape.
Should we attempt to bond the new slab to the old? Or should the new slab float independent of the old, with some sort of separation membrane? Would we be better off REMOVING the old slab completely?
Thanks in advance for all input.
Replies
My guess is no. You are going to disturb the soil around this slab & no amount of fill and compacting will equal 40 years of gravity.
I'll also guess cracks over any cuts you make in the existing slab.
Now wait for Gabe and you'll have the real answer.
Joe H
enlarging footprint on 3 sides of the slab.
You will never get the surrounding soil to the exact compaction of that under the existing slab.
IMHO, remove the existing and compact the entire footprint.
SamT
"Law reflects, but in no sense determines the moral worth of a society.... The better the society, the less law there will be. In Heaven, there will be no law, and the lion will lie down with the lamb.... The worse the society, the more law there will be. In Hell, there will be nothing but law, and due process will be meticulously observed."
Grant Gilmore, The Ages of American Law (New Haven: Yale University Press, 1977), pp. 110-111.
From 32866.117
Don't even consider leaving the old slab. Build up the grade with quality granular material and compact till you get 100% and then build on top of it.
Gabe