Slab insulation..

[xwild]

Have had my 30x64 built for 2 years now. Finally realized I'm not going to get around to doing the floor on my own, so I'm contracting it out to a local concrete contractor. They don't do radiant though - they leave that up to either a plumber, or owner.

I'm going to have a 6" slab with fiber. Not planning on any rebar or mesh.

My thought for insulation is 2" Formular250 vertical from top of slab down 2 feet on all 4 sides. Then either Crete-Heat or Amvic Ampex under the slab, depending on what I can get for a decent price. Leaning toward Crete-Heat. I know it's not as cheap as tieing to mesh, but my back and my time is worth the cash.

Then use Radiantec for all my plumbing needs.

Thoughts?

 

[Basketcase]

just finished my pour last week (after 2yrs like you). I used the Amvic Ampex for my 2700sqft shop. You won't regret it for the pex if you can afford it. I actually got mine as "seconds" direct from the manufacturer here in Toronto and got it for roughly half price. I did a 6" slab with 1/2" rebar (had a bunch from a job site that was throwing it out, bonus of working in the trades). I did 2" SM board around the perimeter for the thermal break. See if I can post some pics.

 

[Basketcase]

 

[Jking24]

I used formular 250 under aswell as on the perimeter then attached tubing to 3/8 rebar. All components and tubing came from radiantec

 

[xwild]

just finished my pour last week (after 2yrs like you). I used the Amvic Ampex for my 2700sqft shop. You won't regret it for the pex if you can afford it. I actually got mine as "seconds" direct from the manufacturer here in Toronto and got it for roughly half price. I did a 6" slab with 1/2" rebar (had a bunch from a job site that was throwing it out, bonus of working in the trades). I did 2" SM board around the perimeter for the thermal break. See if I can post some pics.

Thanks! Gorgeous shop! And I see the dog is already claiming it's spot.

Lucky getting it for 1/2 price. I'm just hoping I can get it for a reasonable price. There's a few distributors of the Ampex nearby, and I have a trailer to haul it.

It looks like the Ampex actually has a bit of a hook built into the overlap? As opposed to the Crete-Heat which appears to be just a shiplap?

 

[xwild]

I used formular 250 under aswell as on the perimeter then attached tubing to 3/8 rebar. All components and tubing came from radiantec

Did you use them for your layout as well? How were they to deal with?

 

[Jking24]

Did you use them for your layout as well? How were they to deal with?

Tubing and rebar were on the same centers so Tubing was ziptied to rebar. Worked fine. I should have used more ties i was unaware that the Tubing floating in the concrete was a thing but a couple of ties got knocked around and we had a small area were the tube floated up. The finishers caught it and were able to fix it before it was too late. The other method above were never suggested to me so i wasn't aware the even existed. I didn't like the idea of the ribbing stapled to the foam. I'm not a engineer but i felt like you'll get the most out of your system if your Tubing is completely encapsulated in the media in witch it is to heat. My slab is 5" so we used pieces of cinder block in place of rebar chairs. This put the rebar a little over a inch off the bottom and the Tubing roughly in the middle of the slab. Time will tell if this was the right choice. The heat is not on yet but the slab is almost two years old now and still looks great

 

[GeddyT]

I did exactly as Jking24. I used 1-1/2" dobies to lift a #4 (1/2") rebar grid up off the bottom. Zip-tied 1/2" PEX that I got from Amazon to the rebar grid. 2" foamular250 perimeter to the footing (so below the frost line) as a thermal break and 2" foamular250 underslab.

I liked the idea of lifting the tubing higher up into the slab for faster heating. With a 6" slab, the tubing is pretty much right in the middle. The downside is that I had to be very careful to map out the location of the tubing for any future anchor drilling. Even with a very detailed map, I was absolutely sweating it when bolting down the air compressor. For a lift (that I may or may not ever get around to), I just left two pretty decent sized squares in the right spots with no tubing at all to worry about.

Those pre-formed sheets mentioned above are pretty slick, but were well out of my budget. Tying PEX to the rebar grid really didn't take much time, but my shop is also a lot smaller. And my rebar grid existed, and you're going with fiber. If you've got the money, I don't see any problem at all with your plan. Good luck!

 

[Don1357]

Up here there is a ton of 4' by 2' cement backed 2" foam. Ages ago the roof of buildings were covered on this stuff so every time a building comes down a ton of the stuff enters the market. I managed to get them at $3 a sheet.

• Cement guy and dirt guy were two different people.
• Dirt guy came in and digged, filled, and formed to specifications to accommodate the slab and edge with the extra 2 1/2" sheet of insulation.
• Cement guy came in and installed the perimeter forms.
• I came in and installed the insulation.
• Cement guy came back and did the rebar.
• I came back and attached the PEX to the rebar and built the form for the pipes to come out and into the pressurized manifold.
• Cement guy came back and did the pour.
• I covered the slab and kept it wet.
• Cement guy came back for his forms.
• I worked with dirt guy so the edges of the slab got surrounded by the insulation 2 feet down, double the insulation on the corners, then he backfilled the whole thing.