New garage time!
- Thread starter fatjay
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Wobblin-Goblin
Gold Member
That's a pretty neat method for elevating rebar.
BTW, I'm late to this thread, but whoever told you to keep the pex within 1-1.5" of the top of the concrete doesn't know what they're talking about. It should be that much from the bottom.
BTW, I'm late to this thread, but whoever told you to keep the pex within 1-1.5" of the top of the concrete doesn't know what they're talking about. It should be that much from the bottom.
dodge man
Super Star Member
I also have problems with the pet being that close to the top of the slab. If it’s to shallow the concrete could be weak and crack. I would take a long hard look at that plan.
EddieWalker
Epic Contributor
Interesting idea on using PVC pipe for chairs. I would have waited for chairs. I hope you are not creating weak areas by using the pipe which will stop the concrete from being as strong there compared to the rest of the slab. Are you going to tie the rebar together after you install the wire?
deezler
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Since you didn't lay the PEX yet, I'll chime in: Don't put it within the top 2 inches of the slab.
Concrete is pretty thermally conductive (more than water, even). No matter where the PEX is in the slab, the concrete will conduct heat throughout its entire mass to achieve a nearly uniform temp. Yes, with the PEX at the very top of the slab you might get heat into the building a touch sooner on startup, but then you will still pump heat into the entire concrete mass. But putting the pex at the top puts it very much at risk! You know that you need to cut control joints in your slab to control the cracking, right? You should cut these joints 1/4 of the slab thickness. This would intersect with your PEX plan. You may also want to anchor things into the slab later (risky, but if you know how deep the PEX is, you can get away with it).
In my 30x36 pole barn with 4-6" slab, I put my rebar on 2" chairs and tied the pex directly to the BOTTOM of the the rebar. I don't even really understand using mesh, btw. Solid rebar on a 1-2' spacing accomplishes all the slab control you need, mesh doesn't do much above that. But I did add fiber to my concrete mix (cheap!).
Nice improvising on the chairs, btw! I think that will work nicely. I bought mine off amazon, they were readily available as of 3 years ago anyway. Also my rebar ties.
Concrete is pretty thermally conductive (more than water, even). No matter where the PEX is in the slab, the concrete will conduct heat throughout its entire mass to achieve a nearly uniform temp. Yes, with the PEX at the very top of the slab you might get heat into the building a touch sooner on startup, but then you will still pump heat into the entire concrete mass. But putting the pex at the top puts it very much at risk! You know that you need to cut control joints in your slab to control the cracking, right? You should cut these joints 1/4 of the slab thickness. This would intersect with your PEX plan. You may also want to anchor things into the slab later (risky, but if you know how deep the PEX is, you can get away with it).
In my 30x36 pole barn with 4-6" slab, I put my rebar on 2" chairs and tied the pex directly to the BOTTOM of the the rebar. I don't even really understand using mesh, btw. Solid rebar on a 1-2' spacing accomplishes all the slab control you need, mesh doesn't do much above that. But I did add fiber to my concrete mix (cheap!).
Nice improvising on the chairs, btw! I think that will work nicely. I bought mine off amazon, they were readily available as of 3 years ago anyway. Also my rebar ties.
MossRoad
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If you use rebar wire and tie it at each rebar intersection, you can put the PVC chairs under the upper rebars instead of the lower rebars, like in the picture. What that'll do is lower the entire rebar grid by the diameter of whatever it is. So you'd gain 3/8" or 1/2" or whatever it is above the rebar grid, thus lowering your hot water heat grid by that amount down into the concrete.
Definitely some interesting points. I got most of my information here: How to install PEX Tubing in a concrete slab
Couple youtube videos as well. I can understand warm stone logic, and the weak cement arguement. I'm going to have to think on this a bit.
dodge man
Super Star Member
The reason I wouldn’t want the pet that shallow is minimum cover for the concrete. Say you want 2” of cover, which might be ok but say it gets pushed up a little during the pour. Then the concrete is too thin above it.
Mesh? I’m retired but I worked for a civil engineering firm for years. We still speced it but it does end up getting pushed down. On the other hand a good rebar mat tied correctly on chairs can be walked on and is really solid.
My garage is 28’x30’, no footers but a rat wall around the edge. No rebar but mesh, 6” thick. It has a few hair line cracks you can barely see. Its not that critical of a design unless you are putting heavy stuff in there. I’d just hate to see yours not last because the pet ends up to shallow.
Mesh? I’m retired but I worked for a civil engineering firm for years. We still speced it but it does end up getting pushed down. On the other hand a good rebar mat tied correctly on chairs can be walked on and is really solid.
My garage is 28’x30’, no footers but a rat wall around the edge. No rebar but mesh, 6” thick. It has a few hair line cracks you can barely see. Its not that critical of a design unless you are putting heavy stuff in there. I’d just hate to see yours not last because the pet ends up to shallow.
dodge man
Super Star Member
Duplicate this rebar mat and it will hold up you building. This is for a wind turbine.
