Sunboard underlayment

Sukhoi29SU

Wondering if anyone has used anything other than hardiebacker board over a Sunboard radiant panel?  I looked at Ditra however, after talking to technical rep at Ditra I was informed Ditra wouldn’t be covered under warranty as they are not convinced the thin set would be a good bonding agent to the sunboard based on the material used on top of the sunboard.  Warmboard has been approved.  If it all possible I’d like to use an underlayment that doesn’t require screws, as it will save a lot of time laying out a screw pattern that won’t hit pex.  Any recommendations?  Thanks in advance 

hot_rod

What is the final floor covering?
If it is tile or stone you need some sort of CBS cementous backer system, according to the tile manufacturers associations TCA.
.
Engineered hardwood could go right over the tube, some brands have a very thin foam that goes under the wood systems first, some installer still use red rosin paper for moisture control.
.
For carpet you would need some thin underlayment, and ideally a radiant specific pad below the carpet to keep r-value low.

I don't see a way around nails or screws. And construction adhesive in some cases.

An infrared camera attachment for your phone would help you stay away from tubes, if the system can be fired up..

Sukhoi29SU

Thanks Sir for the response.  Floor will be porcelain tile.  I have 1/4” hardie backer board purchased and just laying over tubes to protect them now.  Planned to use them until tile guy recommended Ditra - however, after some research and your response I’m going to go back to the original hardie plan.   Nice thought in infrared camera - although I don’t think system will be fired up by then.  I planned to pressurize the system with air and use a plastic sheet to trace pex in areas that are more complex (like the areas I routed out) or snap lines on the big areas with standard 8” spacing loops.   Thanks again 

PC7060

The manufacturer technical date sheet will say what type of thinset to use over Sunboard. If they sign off of the thinset then I’d use it. 

Schuyler recommends (requires) unmodified thinset under Ditra but I’ve used Versabond and it bonds the Ditra fleece just fine to the subfloor. 

If your concerned it won’t bond, do a test with some scrap to see how well it works. 

Is this the company that produced the produce you used? 

https://www.sunboardpanel.com/

PC7060

You will need to thinset the backer board down to the sunboard in addition to Mechnical fasteners. 

Can you run domestics cold water through the lines while installing? That will show up just as well in flir camera as the heat. 

hot_rod

Sukhoi29SU said:

Thanks Sir for the response.  Floor will be porcelain tile.  I have 1/4” hardie backer board purchased and just laying over tubes to protect them now.  Planned to use them until tile guy recommended Ditra - however, after some research and your response I’m going to go back to the original hardie plan.   Nice thought in infrared camera - although I don’t think system will be fired up by then.  I planned to pressurize the system with air and use a plastic sheet to trace pex in areas that are more complex (like the areas I routed out) or snap lines on the big areas with standard 8” spacing loops.   Thanks again 

I have done that also with a big sheet of plastic as the road map to lay over as you nail, it works fine.
Lay the plastic over the tube, then trace all the lines with magic marker. I always left that "map" with the homeowner on my WarmBoard jobs, as they often would add floor receptacles once furniture was moved in.

Sukhoi29SU

Talked to a rep at blankecorp.com - he said his product would work - but if there’s any concern with the thin set bonding to the top of sunboard , to self level the floor and then apply thin set over that.  Interesting idea, perhaps.

hot_rod

It that one of the products with the very thin, almost aluminum foil covering? I'd be nervous about gluing anything onto those products.
If it is a thicker flashing thickness and bonded well to the wood, maybe?

PC7060

Did you call the sunboard manufacturer?

Sukhoi29SU

@PC7060 I did.  I spoke with him on the phone.  He said he recommended hardie backer because he is ‘old school’, and didn’t know anything about Ditra.  He did mention he didn’t know how the thin set would bond to a piece of plastic — (his concern was the bonding of the thin set to the Ditra vs the thin set to sun board).  I haven’t called him back to discuss self leveler over the sunboard. 

psb75

He doesn't even understand the nature of Ditra. At least he admitted not knowing how Ditra works. It is a very high quality, engineered, German product that has been on the market for decades. "Old school" is fine. There are advancements that have been made in the materials domain. Hardie board is heavy and annoying to cut and handle. There was a time when Hardie board was the latest advancement...and it wasn't "old school."

PC7060

Can you post a link to the manufacturers technical data sheet for the sunboard product?

psb75

https://www.schluter.com/schluter-us/en_US/Membranes/Uncoupling-(DITRA)/Schluter®-DITRA-&-DITRA-XL/p/DITRA

woobagooba

If any of that radiant panel is at risk of getting wet, be careful the panel product you use will not swell. I dunked samples of most all of the options for a kitchen/powder room. Many of them failed the dunk/swell test.

Sukhoi29SU

@PC7060

https://www.sunboardpanel.com/ressources/fichiers/571c35bd0659.pdf

https://www.sunboardpanel.com/sunboard-panel-design.php

PC7060

Thanks, I found that earlier. Pretty much a useless marketing sheet. The TDS should detail the fastening schedule to subfloor along with ANSI type of approved thinset (if any)

Sukhoi29SU

Agreed, I couldn’t find that at all.  I put hardibacker screws through the sunboard and into the subfloor, however, I just sort of guessed on the spacing and just made sure it is seems secure. 

PC7060

Hopefully with a layer of thinset under the hardiebacker board to ensure all voids between hardie and subfloors are filled (per the Hardieboard TDS)

Sukhoi29SU

That would be the plan :  thin set , hardi board, mortar and then tile.  However, I’m also considering a self leveler over the hardi, thin set, Ditra (or blankecorp), mortar and then tile.  

psb75

Each of those choices sound like quite a "sandwich."

Rich_49

Sukhoi29SU said:

That would be the plan :  thin set , hardi board, mortar and then tile.  However, I’m also considering a self leveler over the hardi, thin set, Ditra (or blankecorp), mortar and then tile.  

If considering self leveling material , you could just use a tile mesh , fasten it to your Sunboard , pour the self leveler and tile right on that . Possibility ?

TAG

Surprised the manufacturer does not have better documentation. Maybe go on the Warmboard site and look at the latest information they have in the install manual. Make sure you get it from the main site and not just google as there are earlier ones available and still floating around. The current install manual is very clear and goes through the steps required for the different tile systems -- from wet beds to newer ways of doing. At one time the Ditra product was in limbo ... they had hundreds of installs with it but the manufacturer of Ditra had not approved it for warranty. The older install manual made reference to more testing or something. Not seeing that note anymore.

Have used Warmboard in a bunch of my personal projects going back to the early 00's when it first came on the market. All have been the full subfloor product except one where I used the overlay product in a basement rehab w/ carpet over it. Warmboard uses a thick aluminum sheet and it's bonded to the panel in a way that it is not coming off. Having seen some other like products -- not sure I would feel the same about just having the bond between the thin layer of aluminum some have and the new tile floor system w/o some type of manufacturer assurance.

Personally -- I like old school full wet beds in showers. Over time it's become harder and harder to find the old guys that do them. Current project is full wet bed w/ metal lath in the shower floors and also in one of the smaller bath floors. On two other larger floors my builder went with the traditional cement backer board after looking over the install manual and discussing with his tile sub. Warmboard has specific thin-set that has to be used on the mat systems ... they are modified products and my memory is they set up faster. It's both a grip and flex thing going on with the thinner mat systems. Sometimes you have to go with what the subs are used to using and comfortable working with .. we were using very expensive tile throughout this project and wanted no drama.

The Warmboard Subfloor product is very thick and makes a solid floor like no other. Old school cement backer really firms up a standard floor when properly done. That would be one of my main objectives -- firm with a big room of tile. We took pictures of the floors prior to starting the tile. A couple plastic templates -- black marker to draw the tubes on the backer board as it was going down w/ proper thin-set and screw spacing.

Warmboard also has recommended construction adhesive for use with the product -- you can glue finished flooring directly to the panel. In most cases I do very wide white oak and have to use a combination of glue and nails. We did have one mistake on this project where the floor guys hit a line of Pex .. I can attest to the tenacity of the Al cover and glue

Sukhoi29SU

@TAG thanks for your response.  Warmboard has in fact been approved for Ditra.  My problem is , I didn’t use warmboard - I have Sunboard installed.  Much less technical data and specs for that.  I’ve spoke to the owner on the phone.  There really wasn’t even any install instructions with this product.  I’ve read good reviews about it, though. 

I installed the sunboard over 3/4” advantech subfloor and prolly paid about 1/2 as much for sunboard as I would have paid for warmboard.  At the time, I didn’t consider using the warmboard structural product that acts as the actual subfloor. I did have the subfloor exposed to the elements for quite awhile though. Using the advantech subfloor allowed me to build the house and get a roof on before installing the radiant board. 

TAG

Sukhoi29SU

Understand you did not use Warmboard ... wanting to make sure you saw the tile instruction for the Warmboard. Gives you something more to think about.

The information is lacking on the Sunboard site. Warmboard's is better ... but, still not great. Warmboard does have very good customer service/ technical support and a rep stops over on projects.

It's a shame when you buy a product and then can't get straight answers from the source. I remember looking into Sunboard and being confused about the "composite" panel vs the plywood. The Ecowarm is another that I looked into ... they have a lot of information available and for tile it's only concrete board. I think because the AL layer is quite thin .... they spent more time badmouthing Warmboard.

Have been lucky and able to layout the Warmboard subfloor in ways to eliminate lots of routing.

It sounds like the subfloor and Sunboard should give you a solid floor -- did you glue the Sunboard to the sub?

Sukhoi29SU

@TAG I didn’t glue the sunboard to the Advantech.  I just secured it with screws. That’s the only instruction I received from Jim @ Sunboard.  I couldn’t even find the required spacing for screws anywhere, so I just guessed and made sure to put, what I figured, was enough.  If I end up putting screws through hardiebacker board and through the sunboard , I’ll use 1 5/8” backer board screws which should go through the hardi, sunboard and into the advantech subfloor.  I was just hoping to avoid screws over such a large area where I won’t be able to see the pex…

TAG

You will have to mark out the PEX on top of the cement board based on what the manufacture of the board recommends. I can see where it will be a bit of a pain in some of the areas you have ... but it's just a question of picking up the panel a couple of times. It goes fast in the other areas that are all open.

Who is doing the tile and they layout ?

When I did the Warmboard R -- it was in a basement and I covered the slab with plastic VB and insulation board -- we fastened the Warmboard with Pins after drilling. Warmboard has a faster layout for the R panels and I just followed it. They have both a glue and no glue for the R over subfloor -- the R panel is OSB and the S is plywood. I have done S over an "on grade" slab ...

Again -- it's a shame the manufacture can't provide better guidance. You can't be the first person doing tile ?