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Due to undersized foundation (5" wide x 12" deep concrete wall with no extra footing), low exterior grade to siding clearance, and little to no crawlspace access, and a bad floor that needs replacing anyway, a contractor friend suggested that we temporarily support/level the sills/walls (2.5" square tubing with 4"x4" bearing plates between existing sill and existing stem wall 23" oc on exterior bearing walls, and 3/4" all thread to concrete block on interior partition walls, remove the floor joists, and float in a 5.5 inch slab. It is about a 20' by 25' single story wood frame area, 4 layers of exterior wood siding so LOTs of temporary shear in place, with some extra bracing to prevent kick in/out. Concrete slab to be floated into place in Mono pour connected to and capping existing footing. See the picture for details. The reason for leaving the existing to make it easier to temp support the structure. We think we have enough steel in the design to support the cap part of the slab? Northern Cal, so we are not in a zone where freeze/thaw is an issue, and in 60-years the existing undersized has settled only 1/2" in one corner due to poor downspout management which is being fixed.

Does this approach (working around and over the existing footing in this manner), seem adequate, or should I be focusing on an approach that totally removes the existing footing?

Proposed Slab

  • Good information posted on the idea and plan but what is the question? Your location (where in the world) will also be asked so edit your question and add the question and location. – Ed Beal Jan 13 '17 at 1:58
  • Updated - Does this approach (working around and over the existing footing in this manner), seem adequate, or should I be focusing on an approach that totally removes the existing footing? – GBow Jan 13 '17 at 3:45
  • Please explain how proposed idea addresses "low exterior grade to siding clearance" given the walls are not raised and the grade is not lowered. – James Olson Jan 13 '17 at 13:35
  • Keeping the existing footing will make the job much easier and cost less than trying to support the house while installing the new footing / slab. There needs to be 6" from the ground level to the siding (or that is code in my area). In the 70's I was involved with several updates similar to this in Sonoma county Ca. The biggest thing I can think of is the anchors to the walls we used to just use "J" bolts but I think the code has changed and different anchors may be required but I haven't worked down there for many years. over all I believe it looks like a good plan. – Ed Beal Jan 13 '17 at 14:11
  • The siding currently extends down over the joists and blocking which puts it almost in ground contact. After the pour it will be trimmed off at plate level giving it the 6 to 8 inches it needs. – GBow Jan 13 '17 at 17:31

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