In-Floor Heat Installation

[davesly]

Just completed the installation of the vapor barrier (6 mil plastic from Lowes), the 2" foamboard insulation (damaged sheets from a local manufacturer), 1/2" ThermoPEX in-floor radiant tubing (Pex Supply) and 3 manifolds (ebay).

NOTE: the attached picture in this email of the PEX TUBE LAYOUT PLAN (it is the 7th image with a white background so it blends in with the background of this message and is easy to miss).

The garage is 40x60 (the 20' end is in-set 2 feet on each side). I went with 8 loops that are each about 300 feet long.

The contractor provided the foundation and a smooth gravel base for me to work from. He is putting down rebar and concrete on Wednesday.

 

[jklingel]

Looks good, except for the staples in the ends of the loops. Everywhere I read, and on my son's place the plumber said, "No staples in the loops, only the runs." You may want to check w/ someone else on that, but I am sure that is what Seton and others say. Pls post what you find out. j

 

[davesly]

Good point about the corners. I had not heard that, however I could see how they could potentially bind. I'll cut those loose that look too tight.

We finally got the rebar in. Next step is concrete.

 

[jklingel]

Glad I could help. I have never inquired about exactly why the ends should be loose, but it does have something to do w/ kinking. That rebar looks like tedious work. Good luck w/ the mud; hope you get a GOOD crew. j

 

[Mufrat62]

I will be doing a 24X40 shop this summer and will be going with the radiant tubing. Some companies say to put the pex below the rebar and some say on top of the rebar. Can you tell me what swayed you on the rebar placement???

 

[jklingel]

Muf: Deeper PEX takes longer to raise the temp, but gives a more consistent floor temp. Closer to the surface gives more of a Zebra affect w/ floor temps; warm, cold, warm, cold, but heats faster. Closer also is more subject to puncture if you ever anchor a partition wall, or whatever, to the floor. As long as the rebar is in the correct place, I don't think it matters structurally. That is all I know.

 

[Mufrat62]

jklingel- thanks for the info could be swayed to put it a little deeper just for the fact of the puncture hazard and the saw cuts in the floor to prevent cracking. My contractor requested if I place the pex on top of the rebar he wanted 5" of concrete instead of 4.5" to make sure his saw cuts couldn't get to the pex.

 

[jklingel]

Ask your contractor about the plastic (I think) angle strips used instead of saw cuts. I am not familiar w/ them, but apparently you install them before the pour and one leg sticks up near to top of the concrete, leaving a weak edge there for cracking. If you know/learn more than I do, pls post; I'm curious about them. The engineer that designed my foundation says that saw cuts are worthless and concrete cracks where it feels like, if it does crack. I don't know; saw kerfs and "weakness strips" sound logical to me.

 

[Mufrat62]

jklingel- Yes I will get in touch with him. I think I am of the same opinion as your engineer - if you live where the temperature flucuates from 40 C(100 F) or down to -30 C or -40 F when the ground shifts something has to move. I think my contractor was more concerned that he tie the rebar and not myself. He had no problems with me laying it out but wanted to do tying of the rebar so it was correct. He is not charging me anymore to tie it so I think I will let him do it.

 

[davesly]

I am going with a 5" thick floor, but my contractor REQUIRED the tubes be mounted to the Blueboard so that he would not accidentally cut them when he cut the concrete. I'll have to admit that the tube installation went a lot faster being able to staple it to the blueboard, then having to bend down and install zip-ties all over.

 

[nate379]

Sounds like he has no idea what he is talking about.

The engineer that designed my foundation says that saw cuts are worthless and concrete cracks where it feels like, if it does crack. I don't know; saw kerfs and "weakness strips" sound logical to me.

 

[jklingel]

Muf: Sounds like you have a conscientious mud guy. Great.
Nate: I have no firm opinion yet, but it does sound strange. Sometimes people do "what works" because it really does, and sometimes because they THINK it does. I'll have to keep digging around on this one, but I don't see what a kerf can hurt, and I've wondered why a person can't walk across the slab on plywood sheets and score a deep gash w/ a kitchen knife before the slab gets hard. That sure would not cut PEX, anyway.

 

[DuramaxPowered]

What type of stapler is that? I've not seen one like that.

 

[Flathead Youngin']

man, thanks for the thread and especially the pics....

i'm looking at doing half of my 40x80 this summer, maybe next summer.....

i'm curious, too, where did you buy/rent/borrow the stapler?

did those manifolds seems like pretty good quality?

there was a thread on here somewhere, but i can't seem to find it.....how do you insulate the concrete where it meets the apron outside? what if you don't pour an apron?

sorry for the many ?'s, just trying to pick your brain.....many of these things are you only get one shot at it.....

 

[thammel]

Check out blueridge on the web. I rented a stpaler from them and it worked great. I stapled my pex directly to the 2" thick blue sheet insulation which was placed on top of the 6 mile plastic sheet. Then the concrete guys used wire mesh on top of that. I also had a rim of 1" thick blue foam insulation around the full perimeter so the entire pad is effectively sitting in a foam insulation container.

Tom

 

[DuramaxPowered]

VERY nice!!!!

 

[davesly]

I borrowed the stapler from my local plumber (same guy who looked over my work and helped me with the building inspector). This brand was a WISBRO, howeve there is a MELCO on ebay (search Pex Stapler) for $250 new. Sometimes you can find them used for about 1/2 of that. Staples are expensive ($20 for a box of 300 on ebay, and $60 retail). I used 1200 staples for 2,100 lineal feet of tubing.

I (and my plumber) are happy with the manifolds. The ebay seller is called "pexcompany" and the 3 port manifold was around $170 (quite a bit cheaper than local retail).

 

[davesly]

The driveway is concrete directly to the bulding, so there wil not be a specifc apron. I was not planning to insulate underneath that area. I can see how I could lose some heat in that space (hopefully not too much). Obviously there will be an air gap between the driveway and the concrete floor. Maybe I can fill that gap with caulk and get some isolation.

 

[matt60j]

Looks good! We have close to the same set-up exept my build is 40x56. Also went with 5" of cement. -MATT

 

[Swampy]

Looks Good, how did the pour turn out? Do you recall what your spacing came out to be? I am building a 44x60 and it was advised I space at 8". Yours looks like about 12" in more from the pics. Just curious-


Also, are the three different manifold so you can run different temps through each zone (like for living/work spaces)?


Thanks

 

[davesly]

The pour went great (super smooth and even). The guys are marking the floor for the cuts. They mentioned that they score the concrete more for expansion and contraction, then up/down movement. One tricky issue, was to set the joints 2' from the center of the posts. The manufacturer says that you don't want an expansion joint near (or under) your lift posts (I have 4 posts).

The rebar spacing is every 2 feet. I did the Pex with spacing of 1 foot. I talked to several pex people, and they indicated that 1 foot spacing is fine (max of what you want). There are a few places were I am probably 18", but not many. In addition, the majority of the layout is spiral in and out, so I have a source (hot) next to a return (cold). My plumber said that when everything is stable, there will not be much of a temp difference between the hot and cold sides.

The three manifolds were more for the future owner than me (i.e. in 20+ years). I am building the garage, so that it could be converted into a mother-in-laws quarters, if the new owner is not a car guy and needs an extra living space. I tried to think about what zones I would want if I was converting this to a living space.

Since I had to attach this garage to my house (building zones), I needed to design it to look more like a house expansion than a big garage. I've got overall pics of the entire project (3D sketchup plans) in the Garage Gallery Forum called "40x60 attached colonial garage".

 

[davesly]

One other interesting note: I had the plumber stand by during the concrete pour, just in case the concrete guys messed up a pex tube. The plumber was ready with a patch kit (just in case). Luckily his services were not needed.

You can imagine how difficult it would be to have a problem with your pex tubes during the pour and then needing to find someone to fix it before the concrete sets up.

 

[davesly]

By the way, I did include a picture of my PEX tubing spiral layout in my first message. Unfortunately, it is the 7th picture with a white background and is easy to miss. This layout is entirely 12 inch spacing for a 40x60. I also routed the outer tube about 2 inches from the outside wall. I did the drawing in AutoCAD.

 

[Mufrat62]

Good idea about the plumber. He is coming to test the system when I do mine but having there during the pour would be even a better idea.

 

[Laner]

davesly -did you create a thickers section of concrete around the perimeter of the slab? Also, did you bury any insulation below the slab at the sides?

 

[davesly]

Laner
The concrete thickness is consistent (5 inches) all around. The side insulation goes down a few inches below the 2inch floor insulation. It is probably a good idea to have the side insulation go down deeper, however they had already poured the foundation and leveled the gravel when I thought of this.

 

[bimmer1980]

and I've wondered why a person can't walk across the slab on plywood sheets and score a deep gash w/ a kitchen knife before the slab gets hard. That sure would not cut PEX, anyway.

I guess you haven't done much concrete work.........

They do make tools for putting in joints in concrete while you are working it..... However, you have start with the grooving tools early in the pour and keep at it... I don't like them because you end up with a radiased edge groove.... a 1/8" wide saw cut groove is the way to go.


To the OP--Nice looking slab!