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Concrete slab to foundation work

8K views 3 replies 3 participants last post by  walkman 
#1 ·
I am considering expanding the laundry room of my home by about 2' by 6'. The 2' area would be pushing the room outside the current perimeter of the house. The room sits on a slab. I am guessing I have to extend the slab out for this project so my questions are - for a 2 * 6 slab butted up to the existing slab do I;
1.) need to build a "footing under the new slab?" and if so, some details
2.) how thick should the new slab be?
3.) how do I attach it to the existing slab ?
4.) do I need a cement slab or can I form something out of 2 by's and attach this to the current slab?
Ultimately I will build 3 walls on the new slab and tie it into the current wall and I'm concerned about the slab sinking in time and ruining all the other work.

Thanks for your thoughts.
 
#2 ·
Steps:

1. Talk to your local code enforcement official, you probably need a permit, plus they will be able to tell you the local requirements for depth of footing, thickness of concrete, required reinforcing if any, connection requirements to the existing slab, preparation work for the subgrade, required anchor bolts, and required details for the walls.

2. If you still have questions, there are many on this forum who can assist with specific issues.
 
#3 ·
Thanks but still need some answers

Thanks Daniel,
Unfortunately, my community code people are not that helpful. They want a permit and expect work to code but will not tell the code or provide direction - they expect you to know - sounds like the intent is to discourage the dyi'er. I will certainly try and comply but the main question exists - what is needed to extend a floor out like I suggested?
 
#4 ·
Your building dept is probably not being helpful because your questions are too basic and they don't want to design the addition for you.

Have you thought about getting an architect for the addition? Besides the foundation you are going to deal with issues of wall structures and how to tie to your existing structure, as well as issues with tying into your existing roof.

An architect will make the addition look much better and show the construction details you're asking about.

An experienced design/build contractor may be able to do the same thing and you could potentially work with him to allow you to do some of the work.

Back to your question: Yes, you will need a properly size footer, or monolithic slab. You will tie it to existing slab by epoxying dowels to connect the two slabs. No, you can't build out with 2x and expect to have it last or pass inspection.


P.S. You are starting a very expensive process for such a small gain in space. If you are going to all this expense you probably ought to design a bigger gain in footprint.
 
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