Installing Hardwood Floor Directly Over Pex Al Pex and Heat Fins?

Brando

Hello everyone. We constructed a subfloor with OSB with grooves for the heat fins and pex. It has been our intention to install the hardwood floor on top of the OSB/heat fins/pex, but are wondering a couple of things:

1. Will the fins, which are not exactly flush with the OSB, cause an issue with the hardwood floor?
2. Do I need to place an underlayment between the subfloor/pex and the hardwood? Would heat affect the underlayment?

Here's an image of the subfloor. As you can see, we have yet to install the fins and pex:

EdTheHeaterMan

I'm seeing a half circle groove at the end or ever other run of strait groove in the subfloor. Are you asking if a grooved aluminum plate can be placed in the groove then the tubing placed on top of that aluminum plate?

I don't believe that will be very easy to do. I might consider just installing the tubing then putting a 1/8" to 1/4" underlayment over the tubing then placing the finish floor over the underlayment.


Has the layout been properly designed so the tubing loops are not too long? What was the floor covering design criteria?

Brando

Hi Edward. I cannot answer your question about tube length. The plan is to attach double-grooved, omega-shaped heat transfer plates to the subfloor and then tuck the pex tubing into the plates. If that's all good, I am wondering if I can install the hardwood floor directly over the fins and pex, or do I need an underlayment. I am concerned that the low profile of the fins may affect installation of the hardwood.
Thanks for responding. I really appreciate it! Brando.

EdTheHeaterMan

That is the only way I would install the hardwood floor. Especially if you are doing conventional hardwood floors where the nails are hidden in the groves of hardwood. How else can you be sure of the tubing location in order to avoid putting a nail in the tubing? Are you sure this was the intended design of the floor heating tubing? I'm guessing that you are not the designer of the radiant tubing. You must be the floor installer. I'm thinking of the noise that aluminum plates might make when the floor is walked on and when the tubing changes temperature. Also you must put in your floor installing agreement that you are not responsible for that noise and that you are not responsible for the wood floor drying out as a result of the tubing temperature going too hot.

Do it in writing!

hot_rod

What type of flooring? 3/4” T&G nailed over the “proud” plates?

There are some plastic grid systems where flooring or subfloor goes over the plates. Check with the plate manufacturer

Floor leveling grout between the plates would level the surface.

Brando

Thanks again, Edward. I want to make sure i understand you correctly. I think you are saying that pex without fins and with an underlayment is a better choice than pex with fins. I had not considered the noise factor, but I can see how that may be an issue.

Also, are you saying NOT to place an underlayment OVER the heat fins? What is this issue with that?

Have you observed these issues in your work? Do you know of an example where the heat fins under the hardwood floor created noise or some other problem? I have found manufacturer websites that recommend this "sandwich" construction, so I am looking for someone with real field experience to provide some guidance.

hot_rod

The U type fins were developed for installation like yours, nailing flooring is no different then Warmboard, Roth, climatePanel and dozen other wood panel systems

l made maps  of the tubing with butcher paper and a marker, keep it always.

www.launstein.com had done a lot of wood over radiant research, some videos at their site

The movement of wood has more to do with humidity control as you will see at their lab

Some species lend themself to radiant better than others

For years the RPA published a floor covering guide detailing all the various methods and precautions. Might still find them online.

some hardwood installers insist on a slip sheet, red rosin paper, under hardwood others avoid it

Brando

Thanks to all for these great comments! I have another question: How do I attach the fins to the OSB? Staples? Nails? Other?

hot_rod

If they are the thin gauge, flashing aluminum thickness, staples work
If they are extruded aluminum, some are pre punched for screws. I’d hit them with a countersink bit and use wood screws driven flush.

Brando

Thanks again! I really appreciate it!

TAG

Those twin groove plates are quite thin ... you will have to see if the flooring joints that fall away from a plate show the height deferential. It's an easy fix to slip a scrap of the AL under the nail location on those that need it

Don't think you will need to do anything to hold the plates in place -- the flooring and nails will hold. I have done a lot of wide plank flooring with warm-board and glue/ nails .... that works well but you must use the correct glue. Someplace you will have to use glue if the floor is parallel to the tube.

A little glue will solve any problems. With constant circulation I have never had any floor sounds