Radiant Floor Question

Ironman

@hot_rod
and any other radiant pros:

I have a large house under construction where we’ve installed about 4,000 square feet of staple up with Rehau plates. The builder and the floor guy want to put the finished flooring down using staples at every 4” instead of the traditional method of blind nailing into the joist at 16” o.c. The sub floor is 1” Advantech.

They want me to have the radiant up and running when they do this. I’m totally against this approach, but what say ye pros?

DJD775

@Ironman What type of finished flooring are they using? If it's strip/plank hardwood then nailing 16"oc would not be acceptable unless that's the manufacturers specification.

STEVEusaPA

I'd initially say the flooring guy is lazy. But that's how they do it now. Unless his staples are less than the thickness of the flooring plus 1" for the subfloor. And even then there's always the chance of one over driving and hitting the tubing.
I'd air it up, and have them sign a document, prepared by a lawyer stating any staples damage the radiant, it's time and material to repair it.
With the right staples they'll probably never hit the tubing. Unless it was my job. Then they'd hit it 20 times.
I guess the undersides are already finished/drywalled?

DJD775

You need to find out what length staples they are using. If it's 3/4 hardwood over 1" subfloor than 2" or less staples should not penetrate beyond the subfloor.

TAG

I assume this is pre-finished flooring ? If so what does the manufacturer recommend ? What does Advantech say about nailing -- it's just fancy OSB when I looked. Does it need to penetrate the panel ?

16" OC is not going to be enough and it never works out --

IMO staples are better. I did a bit over 4k of very wide/ long board white oak with staples and glue over Warmboard -- almost the whole house had to run parallel with the tubing. You could mark the tubes and glue in that area ...

Make sure the floor guys factor the angle of the staple .... even with Warmboard having the tubes visible the did one run too close and hit it about 20 times along a run. Thankfully where it happened was over a crawlspace and it was noticed the next day when the boiler lost pressure.

We did have the system running when the floor went in ... a little glue can be your friend

hot_rod

If it is T&G 3/4 hardwood the flooring pros tell me a T shaped serrated nail is the best, actually called a cleat. It nail through the top part of the tongue.

Those cleats come as short as 1-1/2" I think.

One trick that I learned at a hardwood training session was to put a block under the back of nail gun, that changes the angle the cleat drives into the floor and prevents it from coming out the bottom.

If you have a full 1" subfloor, you should have plenty of "meat" to work with.

Some installers use staples, not ideal according to the classes I attended, more prone to loosening up and causing squeaks, but cheaper to shoot.

Are they putting a red rosin slip sheet down? The eliminates the ability to see the joists anyways.

heathead

Check the red rosin slip paper. I had a flooring contractor want to put some paper down. I split the paper in half and it had a tar smell to the inside. That could have been a big problem with the smell when the heat came on.

mattmia2

I'd be more concerned about the staple that doesn't pierce the tubing immediately but chafes through it after a couple years.

TAG

mattmia2 said:

I'd be more concerned about the staple that doesn't pierce the tubing immediately but chafes through it after a couple years.

Nail can do the same

TAG

It seems the guys that do wide planks like the staple -- the coated really do grab and they don't put as much force towards the previous board. The nail really pulls it all together and that's not always what you want with wide planks .... maybe typical strip red oak where you have a million joints.

I have certainly had to tighten up my share of old nailed floors.

DJD775

Putting a hardwood floor in is just like installing a boiler in. An installer that follows best practices is more important than whether you use nails or cleats.

STEVEusaPA

heathead said:

Check the red rosin slip paper. I had a flooring contractor want to put some paper down. I split the paper in half and it had a tar smell to the inside. That could have been a big problem with the smell when the heat came on.

I've used the tar paper under wet bed a few times, even my own house. No one ever smelled an off gas.

DJD775

All the red rosin paper I have seen is a single ply. Maybe he is referring to a composite product that contains a tar layer and not the traditional rosin paper.

hot_rod

My experience is you have to get SWT above 150 to get some of those papers to off gas. The thin black or beige is asphalt impregnated paper. I don’t think true tar paper has been around for many years

It was a high temperature rubber tube staple up job that I learned of the off gas, 1950 or older home.

Ironman

The finished floor will be 5-1/2” oak t&g and they want to glue it directly to the Advantech.

hot_rod

A solid wood flooring? Usually you want to let that move a bit, it will as humidity changes. That is the purpose of a T&G joint, it hides small movement.

If it is glued it may panelize, where large sections all move as one and pull joints apart. Looks really ugly when it happens.

TAG

The most important part of a flooring install is for the building to be conditioned and the floor acclimated to the space. When doing wide plank you must coat the back side with finish.

The glue is used sparingly and is only on the bottom face .. not in the T&G. Winter is best with the heat on.

Strange things can happen when the building is not conditioned .... the framing and subfloors move when the building is finally able to dry out ---- can see where the subfloor dried and pulled the finished floor apart.

There are specific adhesives best used ....

hot_rod

flexible flooring adhesives, not wood glues like Titebond

TAG

hot_rod said:

flexible flooring adhesives, not wood glues like Titebond

Warmboard has a list of approved glues for hardwood flooring. Flooring adhesive is not the same as subfloor adhesive although I'm sure you could use it for a subfloor if you wanted to spend the money.

Warmboard has our new construction beach house on the website where we did set length clear 8" white oak. Our PA home was in an historic stone building so we used a wider character white oak from a local mill. Long random lengths -- some of it was 14" wide and 16' long. We needed more glue on the wide product.

Here is a picture of the PA floor where we had to pull up a board to fix where the guys punctured a full row of the tube -- unfortunately, we did not get to them fast enough and they started to cut into the subfloor --- the best way is to use a hole saw to patch in the tubing.

The OP should call/ email Advantech -- they show a proprietary adhesive ... but, they also mention using an underlayment (if required). Guess if a VB is needed -- not sure how you can glue doing with that. They also mention additional steps required if the flooring is going in parallel to the joists. All too often nobody reads the instructions