Concrete Questions

Warmer the better for the pour, but your supplier can fix you up with the proper mix even in freezing weather.

Mine is 4", poured 25 years ago. We've had a 18,000# dozer in and out of it for many years and never had a problem. We use old snowmobile tracks to keep the cleats from digging up the surface.

I'd take a serious look at putting the PEX in even if you cant afford to hook it up till later.
The PEX has its good points and bad. If the heat hasnt been on for a while, and its cold out, it'll take a day or so to heat all that concrete before you start to heat the room. However there's nothing better in the middle of winter than having a nice warm concrete floor to work on.

The guy who helped me had a concrete business and said it was the only way to go. 24ft x 32ft span and we cut in 4 expansion joints. No cracks after 5 years and we get a fair amount of temperature swings.

One thing I did that I have always been happy about is I put in a floor drain. I can wash cars and hose the floor down and it cleans up fine. I even run my boat in there and just let the water run down the drain. Up to you where it goes after it"s in the drain but I just ran a 4" PVC line out the side and let the water seep in to the ground.

I have compacted sand under my floor. West Michigan is pretty sandy so it"s never a big deal to get. Overall the soil drains well here as you would expect.

The others are right about putting in whatever you think you may need in the future. One thing I like to do is run a 1.5" pipe under the concrete anytime that I pour in case I ever need to fish a wire or something under it.

Beyond that, your concrete supplier should probably be able to provide an admixture to the mix design to prevent freezing. Concrete creates heat when curing, definitely pour early in the morning, it's the best time when cold out as daytime temperatures rise and you have natural light, use woven wire mesh 6" x 6", make sure it's centered in the slab thickness, not on the sub base or ground, pull up on it with a hook, end of a rake or other hand tool while pouring. #4 bars can be used around the perimeter or where you may have higher stress points, like at the entrance etc. Make sure your sub base is firmly compacted and not frozen when pouring, after finishing, you can use thermal blankets to cover the slab to prevent freezing, talk to the supplier about the temperatures you are working in, right now around here, it's 30's-40's, not a problem to pour without any admixtures. 6" thickness would be better for dealing with heavier weights, but properly reinforced with woven wire mesh and or deformed metal bars (rebar), using a 4000 psi mix design at 4" may do the job, but you need to make sure it's well reinforced, I'd prefer 6" 3000 - 4000 psi mix design with substantial reinforcing if live loads from tractors or heavier equipment will be placed on it, for just cars or smaller equipment it may not be necessary, if its a smaller sized slab, and you need a few extra yards for additional thickness, money well spent there.

I used to beef up sidewalk slabs on job sites, when I knew construction traffic would be a factor after it's poured, to avoid fracturing and or failure, especially heading into cold weather with a completion date in that time frame whereas it would be impossible to re-pour it if it was damaged.

I suggest you consider a few things. (1) Put in a drain. And gently slope the floor towards it. (2) Make it 5" thick instead of four (guards against thin areas due to undulation in the sub-base. (3) Mix the gravel with about 25% sand before compaction ( increases compaction). (4) Use a plastizer in the concrete mix (increases flexibility and reduces chance for expansion/contraction cracks.) (5)Use as thick a concrete mix (this is called slump) as the finishers can handle. (6) Consider insulating the floor from the ground (at least the outside of the footing down to footing depth). This will usually pay back in savings in heating AND A/C costs. (7) Buy the concrete from a well known, respected supplier. It is real easy for them to sell you a lessor quality product than you contract for. (8) Make the footing depth and width widder and deeper than the maximum recommended for you area (by at least 10% to 15%) (9) Increase the thickness of the concrete(and rebar support) to 8" or so, in the area six to eight feet in front of any overhead door(s) you may be driving heavy equipment over (this prevents sudden, heavy loads on the perimeter from cracking the concrete. (10) Decide on the final finish you desire BEFORE you start the pour and make sure the finisher(s) know what you want. I prefer a slick finish on a shop floor so you can paint it. Really makes it easier to keep clean. Many prefer a brush or broom finish. Look around town and find what you want BEFORE you start (could affect the sack mix ratio). (11) Do the pour in moderate ambient temperature (say in the spring or early fall). After the pour - stay off with anything heavy untill it has cured some. (12) If it's a large pour, place expansion joints appropiatly. A large pour WILL crack somewhere (by sawing or building in the joints you control where the cracks are). (13) If it is a small pour the 6" welded wire, used with the plastizer, will be adequate for support. If it is a large pour with expansion joints - then by all means use rebar, wire tied on 24" to 30" centers.

Remember - What you wind up with is what you will have to live with, forever. A few extra $$$$$ now can sure make life easier in the future. I have probably left some things out and others can add, agree, or disagree. Good luck ! bob f.

HOPE THIS HELPS STEWART