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RE: Radiant Floor System on Plywood Subfloor

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Hi Jeff,
The tubes are sandwiched between plywood layers. The APA refered me to the Radiant Panel Association and a link with info on the subject:
-----Original Message-----
From: Jeff Smith [mailto:jeffsmith7(--nospam--at)]
Sent: Monday, December 22, 2008 7:23 PM
To: seaint(--nospam--at)
Subject: RE: Radiant Floor System on Plywood Subfloor

I agree you should see what the APA has to say.
I am still unclear, are the radiant tubes in a gypcrete topping on top of the subfloor, are they in a warmboard type subfloor, subfloor plus tubes/plywood sandwich,  or a staple-up type radiant, what is the finish floor?
I would think that a manufacturer of a radiant flooring system would provide strict specifications for the entire assembly. Some systems can deliver water at up to 140 degrees F.  Dry installtions require higher water tempurature. It is my understanding that a 140 degee water tempurature will not adversley effect the plywood subfloor, but it may have an effect on the finish wood flooring or mastic type adhesives. Big, fast temperature changes in humid conditions can effect the finish wood flooring. Therefore there may be limitations on the type of wood, plank size or you may need an engineered laminated wood flooring that is made for such a use. Another issue with tubes directly under finish wood flooring is that it does not distribute the heat as well and may have localized hot spots.

From: Michel Blangy [mailto:mblangy(--nospam--at)]
Sent: Monday, December 22, 2008 2:16 PM
To: seaint(--nospam--at)
Subject: RE: Radiant Floor System on Plywood Subfloor

oops...I'm concerned with temperature. Sorry.
-----Original Message-----
From: David Topete [mailto:d.topete73(--nospam--at)]
Sent: Monday, December 22, 2008 1:24 PM
To: seaint(--nospam--at)
Subject: Re: Radiant Floor System on Plywood Subfloor

"What is the maximum allowable set for water?"  I am unclear about what you're asking...  Are you asking what to add to the uniform DL of the floor?  it wouldn't be much...  I'd use 8-10 psf  per inch of gypcrete topping that the radiant system is encased in.

On Mon, Dec 22, 2008 at 1:00 PM, Michel Blangy <mblangy(--nospam--at)> wrote:
Seasons greetings list,

I think this is on-topic...

For a radiant floor system with tubes installed in direct contact with the
plywood subfloor, what is the maximum allowable set for water?

I have an inquiry in to the APA, but thought I'd try here also.


Michel Blangy

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