I own a tract house built in southern california built in 1995. There was a builder option to have a 3 car garage (standard 2 car with tandem garage) or a super family room where the extension creating the tandem garage is used as part of the family room instead of garage. My house currently has the 3 car garage and I would like to convert it to the super family room. I pulled the original building plans (which are terrible quality) but I can tell that the current wall separating the tandem garage from the house is not load bearing. I feel like this should be a fairly straight forward conversion but after talking to drafting professionals and contractors they seem to make it out to be a much larger job and have left me with a couple specific questions:

The current garage floor slopes from back to front (as expected) 1 3/4 inches to 4 inches. I am wondering what the proper way to level this flooring is so I can conform with building codes?

Does this require a structural engineer (as has been suggested by a couple drafting professionals)? I thought it would just require additional concrete with some bonding agent...

(Updated 5/18/18) I had one architect+engineer tell me that the city is going to require the slab be replaced because it was not constructed with a moisture/vapor barrier under it. Does this sound right to anyone?

Another suggestion made by someone who used to be in construction was to use 2x4's on their side to frame out a floor and shim up to level. Thought I would throw that out there as a possible suggestion and see what people think.

Here are some images so you can get a better idea of the space and slope: Rear of garage

Living space foundation height

Garage overview

  • Did you ever get this resolved? If so, please give a check-mark to the answer or write up your own answer explaining what you did to get it fixed and give yourself a check mark. That will help others with this kind of problem know that this has a resolution and is a good place to look for their answer. – FreeMan Aug 4 '20 at 18:06

I would check Cali codes, but here in WA you can do all of those things you asked about without a permit. It would be considered a remodel and only certain things like some electrical work would require a permit. I personally would frame in the garage door area and use the self leveling product you can buy from the local home improvement store that mixes with water. Works well on concrete. I have used it to level and seal over my old basement floor that consisted of thin asbestos tiles over concrete. Have you talked to a local contractor? Ask friends/family for a trusted remodel contractor that will give you an honest assessment would be advice before doing anything.

  • I'll have to look closer at the CA building codes but they are really hard to read. I have spoken with the city of course they seem to think it needs to be permitted. I think any time you are adding square footage to the living space you need a permit. – german129 May 18 '18 at 16:58
  • Up to 4" of leveling compound would be horribly expensive, I have leveled with 1/8" or turkey grit concrete that works well especially with fiberglass in the mix for additional strength but a floor covering will be needed because the fiberglass tends to have sharp spots after finishing. I have also made wood framed flooring both methods have pros and cons. – Ed Beal May 18 '18 at 18:31
  • @EdBeal do you know if wood framed flooring would be allowed permit wise over the existing garage foundation? Assuming the current foundation isnt an issue, then my next concern is if 2x4 with the 4inch side flat would be allowed since I only have 2 inches roughly to work with at the back of the garage. – german129 May 19 '18 at 23:47
  • I have used wood To level a couple of garages and installed decking on top. Since the wood will be on the slab you could even use furring strips at the back or rip some 2x's to level the floor. – Ed Beal May 21 '18 at 19:15
  • As @EdBeal mentioned, self-levelling would be incredibly expensive, plus it would have to be done in multiple phases, as the most versatile product can probably do up to 1.5" at a time, max. So you'd have to mix and pour 3 times. – FrK Apr 6 '20 at 18:31

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