Head scratcher??

S Ebels

I'm advising a DIY'er on the radiant heating portion of his remodel project and am a bit stumped about what to tell him to do on this one.

He has an existing wood subfloor that he is going to pour 2" of concrete over. On this wood subfloor is some extremely well adhered 40# ashphalt felt. He has tried sanding this off with a floor sander but it plugs the paper up after about 15 seconds of use. Doesn't work. It is stuck to the wood in such a way that it is almost "in" the wood. Scrapeing it doesn't even make a dent in it.

Questions.

Do you think that running standard floor temps will cause an odor problem for him if he doesn't get the stuff off?

Would you advise placing some sort of foam insulation (1/4") underneath the concrete shield the tarpaper from the heat of the floor? I question whether this is a good idea underneath a 2" concrete floor that is going to be the finished surface?

Put some 6 mil plastic over the floor and run it as is?

Any ideas or other thoughts? have any of you actually had an odor problem with exceedingly old tarpaper under a radiant slab.

The tube is on top of the floor so we will not be running high temp water in the system.

Dan Peel

Tar pit

or Tarp It. If insulation is what you are looking for try polytarp. If not your 6 mil slip sheet should be enough. Enjoy...Dan

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hr

Only once have I

had an off gassing with asphalt impregnated felt paper. That was an early, very high temperature staple up.

I'd venture to say 150° or less constant supply would be safe. Mine didn't squirm and smell till the 170-180° range.

hot rod

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Wayco Wayne_2

Double bubble

foil insulation might be a good thing to put in beween the concrete and the floor. WW

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John Felciano

Smelly paper

My own house has tar paper sandwiched between wood with staple up radiant and I've never smelled an odor from it.The floors are rather thick,old farmhouse,so the temperature is in the 150*+ range.The paper is probably 40 years old.

I think if the paper is that old and that dried out it's probably done outgassing.Try heating some up with a heatgun and see if it smells???

S Ebels

Wayco

I'm a little apprehensive about the bubble stuff under a thin slab pour of concrete. With only 1 1/2" - 2" of concrete I have a feeling that it won't support the concrete well enough to prevent cracking. The bare concrete will be sealed and stained and will serve as the finished floor. My gut tells me that at slab temps of 90*s or less he's not going to have any problem with odor in the first place. What do you think?

eleft_4

Same here, my water max. is 135.

Dave Holdorf

\"Tar\" Paper

Steve-

Try getting a small piece of it and putting it in your toaster oven at the lowest temperature setting.

If you don't smell anything this way, the radiant temp is going to be even lower.

Dave H.

Wayco Wayne_2

Hey Steve

I used the bubble stuff years ago when I was doing a 2" pour over an existing slab. I wanted to slow down the heat from entering the old slab. I was at a one day seminar where the guest speaker was Richard Trethewy, and he recommended it to me. Had no problems and job is 8 years old now. If you can insulate from underneath I would just put down a vapor barrier though. WW

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Homeowner_3

follow up to tar paper question

Thanks Steve for checking opinions regarding the tar paper on my floor. Just want to let everyone know that I didn't want to take a chance and am removing the paper with heat gun and scraper - a couple of days of grunt work. I am curious regarding a 2" thin slab. With 1/2" Pex (5/8 OD)leaving 1-3/8" concrete over the tubing, will I have cracks following the tubing? The plan is to acid wash the concrete for finish flooring. Anyone done this before with this thin a slab? Or seen it done? I know the gyp-crete is only 1-1/2" but you usually have a finish floor over it. Thanks in advance.

Mike T., Swampeast MO

Instead of the heat gun you might try this:

Spray liberally with Fantastic or a strong solution of Tide and water. Cover with plastic sheeting and wait overnight. You may well find that the tar paper releases easily with nothing more than a wide putty knife.

Nron_9

finished floor

talk to the concrete guys gypcrete is not made to be sanded and sealed as a finished floor , better talk to the experts and get more information befor you start