Fiberock over Roth Panals on existing slab

Michael Pastrone

Fiberock over Roth Panals on existing slab

I am a HO getting ready to install radiant on my 600sf existing basement slab. I am curious what folks think of my plan, and I have a few questions.

I selected 3/4" Roth Panals for several reasons, including preserving as much of the limited 91" ceiling hieght, needing some insulation, and a simple install. The basement is dry.

The build up is as follows:
- Tapcon screw 1x4" plywood around perimeter for carpet tack strips
- carpet glue Roth Panals (R=4.5) directly to the slab (no vapor barrier)
- staple 1/4" USG Fiberock (R=0.3) to the Roth Panal for thermal mass (I have no plans to seam)
- flooring: rubber pad and nylon plush carpet (total R=1.4)

This build up works out to $4.28 per square foot for the panal, fiberock, and pex.

I thought about letting both panals float, but later decided to solidify it with glue and staples.

The carpet is needed as this room is my home theatre.

One question is do I even need a thermal mass, and is there a better choice than Fiberock. Durock/Wonderboard seems too brittle and difficult to work with.

While the Roth folks have been somewhat helpful, I have had to create this build up design myself. Roth is still writing up their literature.

My heating source looks like it will be a Munchkin T80, with a Vision1 and a SuperStore. The T80 will also drive the existing monoflow system in my 1400sf single story ranch. I will push the existing five year old Burham Oil fired high mass aside in case the gas company gets too greedy.

The Wall has been a great source of info for me. Thank you in advance for your help.

Cheers,
Michael

Unknown

roth floor system

Michael,

DO NOT STAPLE THE DUROCK TO THE ROTH PANEL!!! It will do no good.

try this, glue the Roth panel to the concrete and Tapcon the rock though the panel to the concrete. Use of glue between the rock and panel is optional. Use flex additives (plastisizer?) to the thin set below tile and also to the grout.

Roth has the literature ready.

Steve

Nron_9

roth

is the information on the web site regarding the 1/2 " panels or only by mail ar email

Unknown

roth floor system

nron,

I have a preliminary copy in PDF format that was e-mailed to me by Bob at their home office. 401-267-9044

steve

Michael Pastrone

Steve,

Thank you for your response.
Though it’s volume was a bit loud, I appreciate the input.

I am sure there is more substance to your opinion of the stapling idea than “It will do no good.”
The Roth polystyrene panel is fairly new. Most are unfamiliar with it, let alone how to install it.

This became apparent when the current Roth salesman (Bob), the former Roth salesman (John), and their New England rep (Brad) all provided unique and creative ways to install their panel on an existing slab under carpet.
These suggestions included all manner of laun, equal, wonderboard, staples, glue, etc.

The build-up I described, glue/panel/Fiberock/staple, was Bob’s suggestion. I initially liked his suggestion to use Fiberock, as I mentioned. Several of its properties made sense, including being easier to work with and only 1/4 inch thick.

I constructed mockups of build-ups that seemed to make sense to me. They included elements of the suggestions I have received, including yours (“Tapcon the rock though the panel”).

Since your response slightly missed the questions implied, I will try to be more clear regarding my application, and explain the new build-up (#B) I plan to use.

Application: Roth polystyrene radiant panels over existing slab, flooring is carpet.

Point A. Underlayment: Fiberock or Durock?
Question 1. Can either of these underlayments be used?

Fiberock is not Durock. They have different compositions and different properties.
Most people in the flooring industry do not know the difference.
Many people in the radiant industry do not acknowledge the difference.

The Material Safety Data Sheets reveal the composition and material stability data (see below).

US Gypsum faxed me an internal letter stating that Fiberock should not be used in applications with floor temps above 85 degrees. This is probably due to its higher cellulose and polymer content.

I want a floor that is not going to breakdown or off gas.

Fiberock - MATERIAL SAFETY DATA SHEET
FiberRock, R value of 0.30
- Gypsum (or Calcium Sulfate Dihydrate) > 80%
- Cellulose < 15%
- Styrene butyl acrylate polymer < 5%
- Crystalline Silica (Quartz) < 2%

Fiberock - CHEMICAL STABILITY AND REACTIVITY
STABILITY: Stable in dry environments.
CONDITIONS TO AVOID: High humidity, moisture, contact with incompatibles.
INCOMPATIBILITY: Acids. Exposure to acids must be avoided because the reactions are vigorous
and produce large amounts of heat.
HAZARDOUS POLYMERIZATION: Will not occur.
HAZARDOUS DECOMPOSITION: Above 1450º C - calcium oxide (CaO) and sulfur dioxide (SO2).

Durock - MATERIAL SAFETY DATA SHEET
Durock, R value of 0.26
- Portland Cement 10-30%
- Expanded Clay Aggregate (or Expanded Shale) 30-50%
- High Alumina Cement 0-10%
- Fly Ash 10-20%
- Gypsum 0-10%
- Fiber Glass Scrim 1-5%
- Cellulose Fiber 0-2%
- Crystalline Silica <5%

Durock - REACTIVITY DATA
STABILITY: Stable
INCOMPATIBILITY: None known.
HAZARDOUS POLYMERIZATION: Will not occur.
HAZARDOUS DECOMPOSITION: None known.


Point B. Underlayment: Thermal Mass
Question 2. How important is the thermal mass of either of these underlayments?
Question 3. How does R value relate to thermal mass?

The R values of each of these products are listed as
FiberRock, R value of 0.30
Durock, R value of 0.26


Point C. Build-up Construction:
Question 4. Why should the “rock” be attached so rigidly to the slab with Tapcon screws? I am not building a carrier runway!

Build-up #B: (pending)
- Roth panel on existing slab, no glue
- Durock (either 1/2 or 5/16 inch), no glue
- Tapcon screw the rock to the slab

I selected Durock because my sense is that I want less adhesives, more mass, and a thicker floor.


Point D. Roth’s literature:
Regarding the plight of Roth’s literature. I have seen two drafts of their Installation Guide. John provided me the most current one, just before he left. And the current rep was surprised that he had not seen it prior to my showing it to him. Roth has a great product here that has been out for a while. It now comes in 3/4 and 1 inch.

Perhaps it will just sell itself.

Thanks again to Gary Wallace for his initial suggestion to take a look at the Roth panel for my application.


Cheers,
Michael

hr

Another product

to consider is Georgia-Pacific "Dens-Shield" It is much nicer to work with than cement boards (Wonderboard or Durarock)

It has a core of specially treated gypsum reinforced with glass fiber, and protected by a heat cured acrylic coating.

It cuts and snaps like sheetrock and about a pound per square foot lighter. It doesn't crumble and leave sharp edges like cut cement boards.

It can be used on floors, walls and ceilings. Seems like this would give you a little mass, and a good underlayment for thre carpet.

hot rod

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hr

Dens-Shield link

http://www.gp.com/build/product.aspx?pname=DensShield®&amp;pid=2818&amp;hierarchy=brand

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