Concrete Questions

[Beefbuzz]

I've been researching for months and there is soooo much conflicting information that I am now doing circles. I think I have it mostly figured out but I still have some outstanding things in my mind and I want to be armed with enough info to make sure my contractor does it correctly.

1. Does the time between pouring footers and pouring the garage slabs matter? For instance, I am ok using blankets and heaters and such for the footers but I want to wait till it is sufficiently warm outside to pour the slabs, probably months apart.

2. I know the key to a good slab is surface prep. What I can't figure out is how do you compact the hell out of it and then dig down the sides to put in the perimeter foam? I plan to put 2" of foam all around the slab and then pex for future radiant use. Also, how deep does the perimeter foam need to be?

3. I plan to epoxy the floor after it is being built. Is there any special prep I should do, like avoid top sealer? The slab is about 2k sq/ft and I assume I need control joints, can I fill those with deck-o-seal or sonolastic and still have the epoxy stick to the joints?

 

[rburke65]

I'd wait for the warmer weather to place the footers. If you can, I'd go down as deep as your frost level. Seal the floor?mno expert here on your future epoxy question. I used a 'cure and seal' on mine to cure it. Better than not sealing at the time. Your call or other experts will chime in. Good luck!

 

[ConCretin]

I can only attribute the absence of responses to your questions to the lack of detail in your post. Pictures or sketches would go a long way towards eliciting helpful advice. With that said, I'll take a run at your questions;

With regard to your first question; there is no downside to placing your footing and slab at different times.

Question number two is not really clear but if you are talking about frost protection, than you need to extend the insulation out far enough to keep the frost from getting underneath the structure.

With regard to question three, my best advice is to install a proper vapor barrier. If you plan on applying an epoxy floor, it's very important.

 

[Beefbuzz]

Thanks for the responses. Let me see if I can add the correct detail. This is the floor stack-up I plan to use to allow for radiant heating:

vapor barrier
2"foam
pex
rebar
concrete
joint sealant to fill in control cuts
polyurea top coating

Here is the latest picture of the garage.

The big garage is ~2k sqft and the smaller on is ~600sqft. You can get an idea of dimensions by looking at this post. http://www.garagejournal.com/forum/showpost.php?p=3260957&postcount=20

Thanks LLwillysfan, you answered my main question about the time between footer and slab placement.

Question two is about how to dig down 2" wide by a couple feet to place the outside perimeter foam for the slab after you place footers and compact the base. I guess I am just not understanding the process. I would think that you would excavate, place the footers, fill it back in and compact, then hand dig the edge to put the perimeter foam in and compact again?? Perhaps I am just being thick headed here but I am a little confused on how to accomplish digging the edge after compaction to put the slab perimeter foam in.
I guess one idea is to put the foam in the inside of the footer forms before you pour the footers, but I want to know the typically accepted way the vertical foam is added before the slab.

Question three was about whether or not anything should be added (or specifically not added) before doing a polyurea coating (I mistakenly said epoxy). I already plan to put a vapor barrier below the foam under the slab.

The second part of question three is: what do I fill the control joints with that the ployurea will stick to?

Thanks!