Concrete deck and slab foundation built as one?
Hello, I’m Cynthia – new member here. I’m wanting some feasibility advice.
Kansas City climate – on the line between zone 4 & 5.
Original house (1898) is built on stone foundation, with basement. This foundation is in pretty good shape, but engineer doesn’t want it to support any more weight.
Wanting to build an addition with a deck along the side of the house that wraps to most of the back. I don’t want a crawlspace & don’t need another basement. Current exterior walls with little insulation, brittle vinyl siding, and windows that don’t open easily – so a well insulated addition that lets in more light and gives us some extra space makes sense compared to retrofitting existing exterior walls. There will be a deck around the addition with stairs down to grade.
Current house sits 4′ above grade. This is what I’m thinking:
Turndown slab foundation/(monolithic slab ?) at 2′ above grade that also extends beyond the addition to be the finish surface of a deck (Concrete deck or raised concrete patio, whatever you want to call it). I would put the insulation above the slab for the part that is the addition. I can’t find any examples online of a deck and foundation poured together.
Here’s my concerns:
1. Moisture that migrates through the slab from the deck area to the addition area
3. Finding a contractor to form/pour the concrete. It is very difficult to find somebody willing to even answer the phone, let alone do something they are unfamiliar with.
We are doing all of the other work except the structural figurings/permit drawings which are being handled by an engineer. Is it possible to do this foundation ourselves or any suggestions for a different design that we could do? I’ve read a few of the articles on here about a concrete free floor, but then we are back to a high maintenance deck.
I’ve attached some pictures. The black outlined is the original house. The red outlined is the addition. The blue outlined is the deck. One diagram is with inset stairs, the other with typical stairs. The lot is fairly level for the first 10′ out from the house, then slopes away in both directions. Planning to regrade (?) The long portion faces west and the back faces north.
Thanks in advance,
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