New footings under existing foundation walls
I have a 1917 bungalow (27' x 36', one story w/ finished attic). Recently started remodeling unfinished basement with future plans to add 6' addition to first floor kitchen and second floor addition. Doing these as three independent phases so that we can recuperate (mentally and financially) in between phases. Also, the current economy does not support the second floor addition. Do not anticipate doing the second floor addition until maybe 5 years down the road. And this is the source of my angst.
We spent almost 2 years think about the remodel and working with designer and engineer. We have well developed plans with full engineering. Engineering is based on current codes, but I fear codes will change before I begin the second floor addition (5 years down the road).
I cut into the basement slab on labor day weekend as prep work for pouring the new point load and shear wall footings that the engineer spec'ed. Opening the slab reviled no footings under perimeter foundation walls (pour 1917 portland cement walls). I spoke with the engineer and he was not expecting footings and put all new loads on point footings (2'-6" x 2'-6" x 12" thick w/ #4 rebar). So he was not concerned.
I'm concerned about changing code requirements that may come into play after I close up the basement slab. I'm thinking about pouring new footings under the existing walls. I already removed 20' of degraded slab along one wall and 12' along adjacent wall. When I do the kitchen addition, I will have another 20' of foundation open from the exterior, at which time I could add the remaining new footings to complete the perimeter of the second floor addition.
I would pour footings in 5' to 6' alternating sections and do two pours. During first pour I will embed rebar into the footing and leave sticking out, to be embed into adjacent footing during second pour.
How wide of a footing? Foundation wall is 6" plus. Plans for finished basement spec a 6" stud wall on interior for insulation and drywall. I'm thinking footing should extend 6" on both sides of foundation and stud wall making a 24" wide by 12" deep footing.
What concrete mix should I use? I will have a cement company mix and deliver, but what do I order? Should the cement mix be slightly expansive? Is it possible to get a cement mix that expands slightly?
Am I completely crazy and going totally overkill? I like doing things right the first time and want to avoid future headaches. Thoughts??
btw - the soil is clayey sand and well drained. The house is complete level and shows no signs of differential settling.
steve in portland, or