Ok guys I have a 24 square garage with a concrete floor app 20 years old. I plan to pour a 12X20 apron soon here. I would like to have in floor heat coils (pex tubing) in the garage. I have talked to a couple of concrete guys and they have told me that I can pour concrete 2" thick over my current slab with no issues. My thinking (plan) is to pour the apron and an additional 2" of concrete all at once. So what say you concrete guys? Keith
Pin the apron; did they mention any bar or screen with that to hold the PEX in position? 2" seems a bit skinny for our stuff. Might be OK from grammas' car but what about 2000 lbs on a jack stand? ws
Insulation under a heated slab would be preferred. But if you're using natural gas to heat, it's the most efficient, so heating cost might be less of a factor. I'll bet your planned method has been done before, the Garage Journal forum would be a great place to ask: https://www.garagejournal.com/forum/index.php
Yes I plan on drilling and pinning it together. Yes rerod or screen mesh will be used. I haven't figured out exactly how I am going to secure the pex yet, but I'm thinking maybe zip tie it to some mesh. I did see some rolls of foil insulation for concrete for radiant heat. Thought I'd put that down on top of my existing concrete 1st. My big concern is will this hold together or crack up and break into pieces? Keith
Shred a bunch of fiber glass cloth and mix it with the concrete, Especially if only doing 2 inches, which is not very thick for rebar. About a 1 foot square cloth shredded will work .
A 2" cap over existing slab is pretty thin. Rebar is usually imbedded a minimum of 2" from the surface, and also 2" above the base it is poured on. So it might be better to use the mesh that is #10 wire on 6'' centers each way. The sheets are easier to keep positioned in the slab than the rolls. But might have to get them delivered as they are 6' or 8' x 20'. If your existing slab has some pretty bad cracks, they will probably transfer through the cap slab. You can get a product called Fiber Mesh from your concrete supplier added to the redi-mix concrete when they deliver. You should be able to pour it all at once, but probably should put a control joint where the apron meets the slab as it will definitely crack there with different thicknesses. A control joint will let it "crack" in a straight line at the door instead of taking off across your floor area. As mentioned above, dowel or pin the apron to the slab. Thicken the edge of the apron to take the impact of vehicles hitting it every time they go on or off of it. Install 1/2" rebar around the perimeter and 2' centers each way. With adding heating tubes and mesh to tie it to etc, along with being poured on top of another slab, I would recommend going 3". This isn't a one man job to do in one pour, and I wouldn't try to mix it yourself. It takes way too long so you end up with a lot of cold joint problems. Plus by the time you buy portland cement, and the sand/gravel mix, you don't save much money and usually get an inferior product compared to redi-mix from your local concrete supplier. And those bags from Home Depot would cost you a fortune!
Existing slab is in good condition, no cracks or anything, but it was poured with a half concocted drain (that doesn't work) in the center and it all slopes into the middle. I would rather have a nice level smooth floor. I would also like to add radiant floor heat so I can heat this building easier/cheaper. The floor is always ice cold in the winter and sucks the heat right up. When I do a job of this magnitude I get/hire help. I can do all the prep work myself easy enough. This job will require approximately 6 yards of concrete which I will get from local concrete company here. The idea was brought up to me earlier to use the fiberglass concrete, thus eliminating the need for any rebar or mesh. I would still add rebar to the apron portion of the slab. Keith
Yeah, the prep work is simple enough. Except maybe the heating tubes, I haven't dealt with much of that. I have used the Fiber Mesh. I feel it adds to the over all integrity of the slab, but doesn't take the place of the 6-6, 10-10 mesh. I have torn out slabs with the fiber glass and it doesn't compare to tearing out one with mesh. Nice plus for you having no cracks in the existing slab. With mesh the new slab should have a better chance on top of the other one and hopefully stay in one piece. I would just be concerned about pouring it at 2". It will get some strength from the one below it, but doesn't really bond to it.
Make sure to keep indoor slab higher than the apron and put a slight angle where the garage door meets the floor to keep water out... As mike says do not forgo the wire..... I like to use both...
I wonder about cutting a groove in the existing slab for the pex? Then the 2-3" of concrete on top would not be weakened by the tubing.
We are doing a radiant slab over our existing concrete floor 26' X 36' -4" pour fiber reinforced. Meeting with my heating contractor later this week. I will be doing all the set up and having a local company pour and polish the floor. I'll post the anchoring/stands system for the pex the contractor wants me to use, when I have the info.
If it were mine I would use higher PSI concrete, meaning more bags of cement are used when mixing a yard of concrete. Also pour it "dry" or a high slump rate. That also make concrete stronger but harder to work. Google 6 bag concrete and read up on variables that increase or decrease strength. Good luck with your project. Jim
I like spending other people’s money : tear out the old concrete, put in an ACO trench drain in about 6’ or so from the overhead door, use XPS or Crete-Heat for the slab insulation, run your Pex, and use 4” of 4k fibre reinforced concrete. The foil stuff doesn’t work very well. If you are planning on a lift, leave appropriately-sized voids in the Pex for the lift anchors. 5’x5’ for each column is a good idea, so you have a little wiggle room.
Like Redmanf1 said, slope the floor in front of the garage door toward the apron so water that hits the door and in front of it runs away. I forgot to mention that. Torqued455 probably gave the best advice, also the most work. Probably not a whole lot more expensive though, and ultimately a better end result. And if adding a lift later, you might want to make the slab thicker where the posts set.
Well sorry to say I am not going to remove the old concrete. Before I did that I will just leave it as is and pour just an apron. This project has already escalated tremendously. I definitely agree with the sloping from the door out. This garage only has an 8' ceiling, so no room for a hoist. I have a 36'x48' shop with 12'6" ceiling and a hoist already. The idea of the over pour is to eliminate the slope to the center drain (which doesn't work anymore) and level the floor up. To add radiant heat and raise the floor a little bit to eliminate the minor flooding we get most every spring. This garage floor doesn't get a ton of weight put on it. It's used for storage and woodworking etc.. Keith
That opens up your flooring options since you don't need to support a vehicles weight.... You could add the radiant heat and use wood flooring, maybe even tile or a synthetic.
