# Self leveling concrete - garage conversion



## thegogetter222 (May 29, 2012)

Gents,
I am in the middle of planning a large garage conversion to living space.  2/3 of the garage is parking space and 1/3 office space.  The 2/3 part is split in half with declining slabs ending in floor drains.  Can I use self leveling concrete to bring this section of the floor to level? I'd have to cap the drains but shouldn't be an issue and if this is an option I believe I could do it with a few dozen bags of Quikrete self leveling concrete.  Thoughts?


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## mudmixer (May 29, 2012)

How thick would be range of thicknesses for the topping?

What is going over the topping?

Dick


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## BridgeMan (May 30, 2012)

You will have a disaster, trying to use this product for leveling an entire length of garage floor. Read the (fine print) instructions that come with the Quikrete self-leveling product--it will start to set in 20 minutes, meaning the first bag batched will be hard enough to stand on while you're barely batching the fourth or fifth bag.  Also, I think I remember the instructions stating that the maximum thickness should be no more than 1", when I used a bag of it a few years ago.  I suspect your garage floor will need a thickness of 4" or 5" at the thick end to make it level.  Your estimate of needing only a few dozen bags is also incorrect--without knowing the dimensions of your placement, a good guess is that considerably more than 100 bags would be required.


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## thegogetter222 (May 30, 2012)

ok, fair enough.  The center is no deeper than 4" from grade and the area I'm talking about is approx. 8'x8' each side.  Do you think this would be cheaper buying concrete from a service and having it pumped and trialed?  Any cost assumptions?


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## BridgeMan (May 30, 2012)

Ready-mix concrete won't be cheaper, but one heck of a lot less grunt work.  Material cost for 100 bags of Quikrete 5000 will be about $550.  Going with delivered concrete, you'll be paying a small load charge if only needing just under 2 C.Y. (8' x 8' x 2 x 0.35' /27).  You can avoid that by having something else formed up to pour at the same time, to make up the difference--sidewalk, driveway widening, patio addition, etc.  Around here, 6-sack mud is going for $120 a yard, 4 yard minimum.  A ground pump with operator will cost you another $500 or so, meaning your total will be close to $1200 if you throw in some mesh/dobies/expansion felt/curing compound. 

Your local material sources and pump rental could be more or less.  Just give them a call for some free quotes.


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## thegogetter222 (May 31, 2012)

Thank you Bridge, very much appreciated.  I have a meeting with one out of the 3 contractors that I contacted tomorrow evening.  He was the only one that accepted the opportunity to bid.  Unfortunately, that is very common around here.

Again, thank you very much.


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## thegogetter222 (Jun 4, 2012)

Ok, I met with probably the most reputable concrete contractor in town and to my surprise the guy was VERY COOL.  He basically said I had 3 options... Option 1. was to cut the concrete out and replace it.  Option 2 was to use concrete to level it but he said within a few years the bond between the old concrete and new concrete could start to disintegrate and slowly lose structural integrity.  He then suggested Option 3. that I simply use plywood and level it the best I could in preparation for flooring.

So he walked away with no skin in the game but an honest suggestion on a simple and cost effective solution.  Awesome : )

Also note, my decline is only 1.5 from flush grade.


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## nealtw (Jun 4, 2012)

Some other things to think about. In new construction you have 6 to 8 inches of concrete showing on the outside of the house to keep water or moisture away from the wood structure. You always have a curb wall between garage and living space also to control moisture as this curb is always waterproofed. On new constructed 2" foam is placed against the foundation from the floor level down or on the flat below the outside to feet of the floor. The foundation across the opening of the garage is not often brought up to the level of the floor so that floor moves up and down with the moisture content of the soil below.
So if you accept that the floor will be cold and may be subject to movement and moisture. The floor should not have any wood products and the bottom plates of the walls should be treated and the studs should be made slip joints like they use on log homes.
If this is going to be a perminent installation. the driveway should be cut back a couple feet the floor should be removed and the foundation at the opening should be extended up to level. Add foam around the outside and vapour barrier and pour new concrete.


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## thegogetter222 (Jun 4, 2012)

well, damn...


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## nealtw (Jun 4, 2012)

I have done myself, just thought you should have everything before you make a decision on what you want to do.


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## thegogetter222 (Jun 5, 2012)

gotcha, thanks again.  My plan is to fill both drains with concrete and level off the grade with treated plywood using tap screws to keep it in place.  I'll eventually lay the whole floor with 6mil sheeting and lay my locking laminate on top of the barrier.  Install trim around the edges where needed.

Next point of review is the proper way to enclose the garage door openings.  One will be completely enclosed and the other used a the new main entrance.

Thanks again guys


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## nealtw (Jun 5, 2012)

There will always be a chance of water under the floor, I would leave the drains open under the floor. How are you going to stop wind driven rain from entering under the wall at the front? When building a wall under the original header, there is a chance that a moving floor can lift the header. Cut the studs an inch to short and add a block to the side of them to make them long enough. This will give the wall a crush factor so any damage in the future will be kept in this area and not above.


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## thegogetter222 (Jun 5, 2012)

Thanks Neal, are you talking specifically under the garage door framing when you recommend a "crush factor"?  The rest of the garage is already framed and insulated.  There has been times where water has backed up significantly through the drains and into the garage... so sealing them is in my best interest.  I'll need to make the water barrier around the garage door framing my area of focus for this concern.

Thoughts?


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## nealtw (Jun 5, 2012)

Directly under the door is where water could get under the slab and freeze, I wouldn't be to concerned about the rest. If water has backed up in those drains, concrete may not be the best plug, perhaps you could makeshift some fitting that could be glued in.


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## BridgeMan (Jun 9, 2012)

If this is going to be a living space, I don't think freezing should ever be much of an issue--you will be adding a source of heat, yes?  And simply plug the drains by filling with contiguous concrete when you pour the floor-leveling concrete, while making an effort (regrading the exterior surface drainage, adding bentonite subgrade cover, or whatever) to eliminate the source of the drains back-flooding as well.


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## nealtw (Jun 10, 2012)

I have to dissagree with Bridgeman here. There is no protection in a garage floor against water entering below the slab, adding heat to the room dose not help the area under the wall at the front which will be insulated. There is a reason frost protection standards are in effect for foundations.


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## BridgeMan (Jun 11, 2012)

nealtw said:


> I have to dissagree with Bridgeman here. There is no protection in a garage floor against water entering below the slab, adding heat to the room dose not help the area under the wall at the front which will be insulated. There is a reason frost protection standards are in effect for foundations.



So tell us, nealtw, do you really think the OP's garage has no footings?  I strongly suspect that is not the case.  Unless Canadians build homes with attached garages differently than in the U.S.--that is, ending the footings at the junction of the house and garage?  And then, provided it has perimeter footings (continuous across where the main door used to be), what makes it any different than the thousands (millions?) of homes built on concrete slabs with perimeter footings?  Do they all have wet floors?  

The 4 that I lived in (25 years in NM) never had floor water problems.  Guess I was just lucky.


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## nealtw (Jun 11, 2012)

Bridgeman: The foundation wall that joins the two side of the garage seldem if ever is poured full height to the floor, often it is feet below the floor, perhaps that's different in different places, do you want to throw out a gareentee? I would bet that if he drilled thru the floor at the area of that wall, he would find sand at about 6" deep.


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## BridgeMan (Jun 11, 2012)

Maybe it's a regional thing.  I've inspected more than a few homes with cracked (and several that were cracked and heaving) garage floors.  Apparently built as you described, with no footing or stemwall projection to support the floor once its base material settles.  However, a conscientious builder will make the footings and stemwalls continuous, in compliance with the IRC.  Section R403 of that Code states that "all exterior walls shall be supported by continuous, solid  . . .concrete footings . . . " (with no provision for ending the footings at door locations, which would make them intermittent or discontinuous).   Of the 3 residential foundations I've designed for high-end homes in central Colorado, the local AHJ required that garage stemwalls/footings be complete perimeter structures (no breaks at the main or any other door).  I'm surprised that's not the case in Canada, where deep frost could do a lot of floor damage in unheated garages that happen to have moist subgrades.


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## nealtw (Jun 11, 2012)

Well continues wall yes, to height of floor not so much. Evan if the wall is there right under the the floor of the garage, as you are aware that joint is not water proof, of evan water resistant. Now with a driveway level or close to the level of the floor and a crack between driveway and floor. Can you really say water can't cause a problem down the road.
The reason the wall isn't brought to full height is that there some feet of fill inside the garage below that floor and no matter how much compaction is done some settlement is often found and if the front is sitting on the wall other problems are created. 
When the wall is directly under that floor we are required to put in rebar attaching the floor to all the walls of the garage but not enough rebar to build a suspended slab so guess what happens when the soil settles.
Check your code on a garage conversion like this it will call for work on the foundation wall and ask yourself what problems they are trying to solve, just incase.


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## BridgeMan (Jun 13, 2012)

And none of the joints between slab floor foundations and their stemwalls are water-tight, either.  The point being?


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## nealtw (Jun 13, 2012)

The driveway level with the floor with a crack between them would be likely place for water to enter. I didn't say it would I said it could and should be concidered and that's all.


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