Radiant Floor Concrete

[JackReese]

Searching this forum I've found several threads of radiant floor heating under a concrete floor used for auto repair, with lifts, etc. So obviously it is doable, which I thought it would be a problem. But I have a couple of questions about the requirements.

I'm a noob to this forum and to RF heating and still have research to do before going forward. My initial question is I thought the flexible pex under the concrete would cause it to prematurely crack and break? Is there some technique that needs to be done to prevent this that is not done on a "normal" floor? And can I get away with a 4" slab concrete? Is doing RF heating under concrete with cars and lifts a more complicated endeavor (read expensive) than floors in your house for example?

Thanks.

 

[Randy in Maine]

Suggestion:

Find someone (like a good local concrete guy who does some commercial stuff) and see what kind of advice they might offer you. A lot depends on where you are located.

My guy in Maine said that the pex tubing is not a big deal. To minimize cracking he suggested the 4000 psi concrete (less water and smaller aggregate) with fiber and no re-bar for my on grade application. I have 6" of concrete over 2" of insulation. Where my 2 lift posts go (each an area of 4'x4'), I traded out the 2" of insulation for 2" of more concrete (total 8") and no pex tubing (at the suggestion of my BendPak installer) near the lift pads.

My concrete guy was cutting the cracking joints just after the concrete had set up. 99% effective.

Do not forget to install the pull pots in the slab to allow you to have a strong winching location at the "head" of each bay.

 

[koditten]

Searching this forum I've found several threads of radiant floor heating under a concrete floor used for auto repair, with lifts, etc. So obviously it is doable, which I thought it would be a problem. But I have a couple of questions about the requirements.

I'm a noob to this forum and to RF heating and still have research to do before going forward. My initial question is I thought the flexible pex under the concrete would cause it to prematurely crack and break? Is there some technique that needs to be done to prevent this that is not done on a "normal" floor? And can I get away with a 4" slab concrete? Is doing RF heating under concrete with cars and lifts a more complicated endeavor (read expensive) than floors in your house for example?

Thanks.

To make it easier on us that have answered this question time and again, do a search. just type in "radiant heating". You will get so much info that your head will spin. Plan on several nights worth of reading. Then come on back and ask away.

There is an amazing amount of info on this site for you to read about.

Later

KO

 

[conceptmachine]

[QUOTouE=Randy in Maine;4269826]Suggestion:

Find someone (like a good local concrete guy who does some commercial stuff) and see what kind of advice they might offer you. A lot depends on where you are located.

My guy in Maine said that the pex tubing is not a big deal. To minimize cracking he suggested the 4000 psi concrete (less water and smaller aggregate) with fiber and no re-bar for my on grade application. I have 6" of concrete over 2" of insulation. Where my 2 lift posts go (each an area of 4'x4'), I traded out the 2" of insulation for 2" of more concrete (total 8") and no pex tubing (at the suggestion of my BendPak installer) near the lift pads.

My concrete guy was cutting the cracking joints just after the concrete had set up. 99% effective.

Do not forget to install the pull pots in the slab to allow you to have a strong winching location at the "head" of each bay.[/QUOTE]


Was no pex around the lift pads because they drill thru floor or was it because of potential cracking and such causing the pex issues? I ask because I have 2, 10k lb cnc machining centers I planned on putting pier pads under but also planned on putting pex under machines. Also I'll be doing the rebar at 1/2 the hight of slab which was recommended. Did you lay everything right on top of the insulation? I plan on 8" throughout.

 

[Randy in Maine]

My understanding (from BendPak) was that the "no pex" near the plates was to ensure there was adequate strength in the concrete to anchor the lift ie a big monolithic slab.

He also told me that the "normal" is 4" of 3500 PSI concrete so he was not concerned about concrete strength in my set up.

If you don't put the pex under where the big machines go, it won't be a big deal. You are essentially heating a big rock with warm water and not having that tubing under there will not even be noticed.

 

[JackReese]

To make it easier on us that have answered this question time and again, do a search. just type in "radiant heating". You will get so much info that your head will spin. Plan on several nights worth of reading. Then come on back and ask away.

There is an amazing amount of info on this site for you to read about.

Later

KO

Thanks, Ill do that.

 

[BadgerBoilerMN]

We install heated driveways here in Minneapolis and design them all over the world.

Location can effect the design but has nothing to do with the concrete.

All of the residential driveways are 4" of 5000psi concrete with fiber and 66-1010 wire over the PEX.

What is effected by location is the insulation, PEX size, spacing, length, depth and the heat source size and control.

A little professional help would be in order.