Sub Floor Over Radiant Heat Slab - Decks & Fencing - Contractor Talk

Sub Floor Over Radiant Heat Slab

Thread Tools Search this Thread Display Modes
Old 12-15-2009, 06:34 PM   #1
benvolio's Avatar
Join Date: Dec 2009
Posts: 5
Rewards Points: 10

Sub Floor Over Radiant Heat Slab

I have a hardwood floor install over a slab with radiant heating embedded in the slab. I'm planning on using 3/4" sub floor so i can nail the floor ( the only way in my opinion ). I don't have the luxury of the location of the pex in the slab. My question is can the sub floor be adhered to the slab with any hope for success, success being squeak proof floor for ever and ever, or do i need to find a way to tap con or ram set the sub floor to the slab. Thanks for the extra pair of brains...
benvolio is offline  

Warning: The topics covered on this site include activities in which there exists the potential for serious injury or death. DOES NOT guarantee the accuracy or completeness of any information contained on this site. Always use proper safety precaution and reference reliable outside sources before attempting any construction or remodeling task!




Old 12-15-2009, 06:38 PM   #2
rselectric1's Avatar
Trade: Licensed Electrical Contractor and Remodeler
Join Date: Sep 2009
Location: Chicago Suburbs
Posts: 11,858
Rewards Points: 896

Re: Sub Floor Over Radiant Heat Slab

Welcome to CT. Just a heads up, it's protocol here to do an introduction in that section and please fill out your profile. You'll get lot's of great help here after you do that


220...221...whatever it takes!
rselectric1 is online now  
Old 12-15-2009, 06:42 PM   #3
PVC Trim Guy's Avatar
Trade: Remodeling Contractor
Join Date: Dec 2009
Location: NYC/CT
Posts: 33
Rewards Points: 25

Re: Sub Floor Over Radiant Heat Slab

If the plywood is warped you are going to need alot of weight to hold it down until the glue dries. I am not all that familiar with radiant slabs, but I am sure it has to be at a certain depth below the surface, so just use a fastener that is not long enough to hit the pex. But it is a risk, especially if you dont know the guys that installed it. You could always try thermal imaging depending on the spacing it may show up as a big red blur though.
PVC Trim Guy is offline  
Sponsored Links
Old 12-15-2009, 07:02 PM   #4
benvolio's Avatar
Join Date: Dec 2009
Posts: 5
Rewards Points: 10

Re: Sub Floor Over Radiant Heat Slab

We're on the same page. I figured sand bags if I go for the glue, but the more I think about it, the more i figure the slab crew surly smashed them down during the pour. 1 1/4 tap cons should do the trick.
benvolio is offline  
Old 12-15-2009, 08:09 PM   #5
RobertCDF's Avatar
Trade: Custom deck builder
Join Date: Aug 2005
Location: Colorado Springs, Colorado
Posts: 9,177
Rewards Points: 1,533

Re: Sub Floor Over Radiant Heat Slab

As far as I know they should be close to the top... That is the only way to do it right... Just think if you hit 1 how much will that set you back? Is that a risk you are willing to take? I would glue only.
RobertCDF is offline  
Old 12-16-2009, 12:32 AM   #6
Cletus's Avatar
Trade: Tube Installer
Join Date: Jan 2008
Posts: 177
Rewards Points: 150

Re: Sub Floor Over Radiant Heat Slab

Unless you know for certain where the tubing is do not nail or screw into the slab. It's a risk not worth taking.

I use two layers of 1/2" plywood with plenty of relief cuts, to allow it to lay flat. Stagger the joints and staple the two layers together, then proceed as normal with the flooring.

I let the assembly float, but you can set the first layer of ply in your adhesive of choice.

A wood floor that never squeaks is an unreasonable goal IMO. Somewhere, at sometime, it seems that they all squeak. It's part of the charm.
Cletus is offline  
Old 12-17-2009, 10:39 AM   #7
benvolio's Avatar
Join Date: Dec 2009
Posts: 5
Rewards Points: 10

Re: Sub Floor Over Radiant Heat Slab

As far as the tubing, i agree it's not worth the risk. I like the 1/2" over 1/2" method, but am i to understand that overall the floor is in no way attached to the slab? I have always tap con'd the sub floor to the slab with a moisture barrier in between, rather than rely on gravity alone. I have yet to install a squeaky floor using this method. Has anyone ever used just floor cement for a sub floor? I'd love first hand experience, but i still dig the opinions too. Thanks


benvolio is offline  

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Polished concrete floor & radiant heat bcbuilder32 Concrete & Paving 4 04-25-2011 07:03 AM
Ever heard of electric radiant floor heat under slab? IHI HVAC 10 02-27-2009 05:32 PM
Basement Slab with Radiant Heat plazaman Framing 6 10-13-2008 04:35 PM
Radiant Barrier Fact Sheet Ed the Roofer Roofing 0 02-09-2008 08:57 PM
Demo a foundation under a radiant heat slab without disturbing the slab...? wackman Remodeling 18 04-01-2007 11:38 PM

Join Now... It's Fast and FREE!

I am a professional contractor
I am a DIY Homeowner
Drywall Talk is for

At we cater exlusivly to professional contractors who make their living as a contractor. Knowing that many homeowners and DIYers are looking for a community to call home, we've created DIY Chatroom is full of helpful advices and perfect for DIY homeowners.

Redirecing in 10 seconds
No Thanks
terms of service

Already Have an Account?