How to attach, if necessary, a 4″ slab on tamped gravel with a perimeter foundation to the existing house. The job is in Kentucky. The existing house is brick veneer with a basement and the new slab’s height is even with the existing house’s wood floor (on 10″ joists). The length of the addition along the house is 31 feet. The footer and concrete block stemwall of the addition, ( on the three exterior sides ) will be pinned to the existing foundation, but what about the 8″ thickened slab edge along the existing house? This edge carries only its own weight and a 2×4 partition wall. Extend down piers and pin them to the existing concrete? |
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Thicken that edge six inches into the existing foundation, drill and epoxy pins in
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Thicken that edge six inches into the existing foundation
Hunh? Elucidate, por favor.
Arigato.SamT
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Like if he is planing to thicken it down 8" but that will miss contact with the old by 4", then he should dig that edge enough to thicken it another ten inches so he can pin to the old.I did use clumsy language there didn't I
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Gotcha, thicken the new so it drops 6" below the top of the old.
That's what I woulda dun too.SamT
Praise the Corporation, for the Corporations' highest concern is the well being of the public.
Edited 4/26/2007 9:20 am by SamT
Too much constraint with concrete is not good. You need to allow for shrinkage during construction. If the slab cannot shrink away from the existing wall it will crack somewhere. Also, there may be some settlement of the addition, while the existing house is done moving. What is the transition like? If just a door opening, a threshold pinned to one side would allow some movement.
preciate your thoughts.
Thanks for your response. Makes sense. How much movement would be expected up, down or internally in a slab over compacted gravel base and stable soil in relation to the existing house?
There are infinite variables with soil science; there is some good theory and some good empirical data, but for your situation anticipating "some" movement is probably enough. For an unloaded slab the settlement should be very little over a well compacted base. You would want a joint in tile or laminate. Carpet would likely be fine. As far as internal shrinkage...add as little water to the mix as possible when placing the slab. Also, more cement means more plastic shrinkage. For a placement 32' long, you certainly want a center saw-cut. You can preplan the location and put dowels in to prevent differential movement after the cut. Again, keep the mix as stiff as possible. If the ready mix supplier offers superplasticizers and pozzolans (fly ash, silica fume, slag etc.) these will also reduce drying shrinkage. A vapor barrier (required most areas) will help the slab shrink back on itself without engaging the aggregate and cracking.