The Flooring Expert

Q: I have old radiant heat (pipes laid in concrete slab) that works great. We love it. However, I want to remove my carpet (2 kids, 2 dogs - need I say more) and lay some sort of flooring. I like the idea of bamboo but have heard that laminate is the only way to go so the floor doesn't warp. What do you recommend, what is warrantied for use over radiant heat?

Thanks,
Pam

A: I'm a huge fan of bamboo, especially the vertical cane look. Now with 2 kids and 2 dogs, I'd be somewhat cautious about bamboo, dependent on age of your kids and then the size and activity level of your dogs. There are several bamboos which can go over radiant heat floors, including some solids (although the requirements are strict and I prefer to avoid gluing down to a radiant heated slab).

Try looking into Springwood bamboo. Springwood makes a great line of engineered floating bamboo floors. You'll get the great look of bamboo with all the benefits of an engineered floor. I will precaution you to use a good underlayment, but look into the R-value of the underlayment and the maximum allowed R-value for your radiant slab. Sound 6 is a great underlayment for this case, although you can use 3mm cork as well. I would strongly advise not using a 6mm cork, as cork has a naturally higher R-value and anything beyond 3mm cork will cause you not to get all that lovely warmth from your floor.

You can also look into most well built engineered hardwood floors (although always consult your manufacturer), but since you like bamboo, Springwood would be at the top of my list to check out. Also, I would heavily suggest looking into natural bamboos, since they are a bit more durable than carbonized. General rule is natural bamboo is slightly harder than white oak (usually around 1410 on the Janka scale) and carbonized is slightly softer than white oak (usually 1120 on the Janka scale).

There are a few laminates that look like bamboo, such as Westhollow's Asian Bamboo, Wilsonart's Hawaiian Bamboo, and the various Bamboos from Shaw and Alloc. For laminate, use something similar to Sound 6 or find one with an attached underlayment.

Q: We're moving into a 1950s Eichler home with the original (still functioning) radiant-heated floor system. It's a great place, however, the marmoleum floor installed by the previous owners doesn't match our taste (it's a little too close to circus stripes). We're wondering what options we have to replace the floor that won't defeat the radiant heating.
We're aware of cork, and laminate floors products, but are also interested in engineered hardwood options. Is there a maximum thickness we can go with for engineered floors? Do you have any advice or product recommendations for radiant-heating floor coverings?

-- Joe

A: The method of installation for your project will matter on the type of subfloor you have under the marmoleum. If you have a concrete subfloor (which is my guess here based on the type of home) install a floating product. If you have a wooden subfloor you can either float or nail through the marmoleum to the subfloor. You can also glue down to the marmoleum, but you will need to rough up the marmoleum and then use a urethane based mastic adhesive. Certain adhesives, such as plastic based adhesives will not adhere well in this situation.

With a floating install, keep in mind that underlayment is important. 3mm cork can work here as far as a premium underlayment is concerned, but you will lose about 3 - 5% of the heat output from your floor. Sound 6 Barrier is also a great option here.

Product wise you can look into floating engineered hardwood, laminate and cork. In regards to the engineered, thickness is not a matter but I would suggest something with more plies in order to reduce expansion and contraction possibilities from the heat. You should be ok with a 5 to 7 ply product here as long as it is better quality. Products with thicker plies and species layer such as Bellefloor, BR-111, Kahrs and Westhollow are good choices here.

With cork you will have a reduction of about 5 - 6% in the heat output of your radiant flooring system. Beyond that cork is a viable option here and I would suggest looking into the floating cork tiles from APC or Westhollow.

To sum up - a floating installation will be best here and if you look into an engineered product keep in mind that 5 plies or more will perform best.

Q: We're building a new home and intend to include radiant heated floors, with PEX tubing in concrete below grade, and in gypcrete, as part of a sub-floor, on the main level. Although we haven't made our final selection, we're favoring either bamboo or possibly cork engineered tiles. I've read that you prefer not to glue tiles down to a radiant heated concrete floor.
Can you please explain. Also, if floating the floor, how are expansion joints handled when there is no molding such as at fireplaces and interfaces between rooms where the floated flooring meets tiles ?

Thanks, John

A: Typically you will want to avoid a glue down application because of the natural properties of any wood flooring. Wood floors will expand due to heat, so since the heat will be directly transferring through your floor it will expand some. Glue down applications will adhere the floor directly to the subfloor and typically allow for very little movement in the flooring. When you have an application that allows little movement, but a heating method which will cause movement, disaster tends to strike. That does not mean that it is impossible to glue down a floor to a radiant heat slab, but its not suggested.

With a floating floor, or any floor for that matter, when you come up to a fireplace typically you will undercut a portion of the brick so that the floor goes under the brick slightly and has an expansion gap hidden away from view. The other matter would be to install some molding like quarter round to cover the expansion gap.

For a transition to a different type of flooring you will always want to use a transition molding. Most transitions now are built with a locking strip which is anchored to the subfloor using screws/nails or a adhesive (such as liquid nail) then the trim itself is simple clicked into place. Based on the height difference of the two floors you can decide which trim to use, typically hard surface to a similar height hard surface involves using a t-mold, though in some cases you may want to use a threshold or end cap/square nose. In the case of floating floors, the trim will still be anchored, but you will allow for a small expansion gap (most of these trims are overlapping) so the floor can properly move without disturbing the transition.

Q: I am interested in installing cork or bamboo flooring on a heated concrete floor. Is this possible?

Rick

A: It is possible to install either of these floors over radiant heat, but certain details need to be kept in mind.

We'll start with bamboo. Certain bamboo floors can be installed over radiant head, but keep in mind several of them have very stringent requirements. Your best bet for bamboo would be a floating bamboo floor as these are engineered and are better suited for radiant heat. Springwood makes a great click-together floating engineered line which can work very well over a heated concrete subfloor. Some of the solid bamboo floors or other glue-down bamboo floors can work over radiant heat, but typically the require installation by certified professionals using only specific adhesives.

For cork floors these can work over radiant heat, but keep in mind that cork has a natural insulation factor to it. This works out to a rate of roughly 3-5% reduction in heat output per 3mm of cork. For glue down cork floors, this is pretty simple as the floors are pure cork, but with a floating cork floor you will also have to account for the core board being used and any underlayment you install. This sounds like a bit, but in the end it turns out to be very little change in heat and I know of a few cork floor which have done very well over radiant heat subfloors.

You will have a bit more ease on the DIY side here using a cork floor, as the requirements to keep a warranty in tact over radiant heat for bamboo are fairly strict, but you do lose a bit of heat out put. Overall the choice becomes a matter of which floor you would rather have in your home, as both can work in this situation.

Q: Hi good morning, we have a concrete floor in our walkout basement we are putting in an apartment I would love to have hardwood flooring we have radiant heat under the concrete please advise what wood and also at a reasonable price. Sq FT is 850.

Thanks,
Marie

A: Your best bet here is to look into an engineered hardwood floor which is suitable for radiant heat, which most are. Your best bet is to look into some of the higher quality ones which have better built substrates, as this will be far better suited to radiant heat. Good choices here are Saso, Bellefloor, Sun Paratech, Westhollow and Kahrs. If you can float the floor, Saso or Kahrs being great here, this will be your best option, but ensure it is installed over a dense underlayment such as cork or sound 6. You can do glue-down, but many floors have very strict requirements for doing a glue-down floor over radiant heat, but not impossible.

Another good option here would be to look into laminate or cork. Both are suitable for radiant heat and in the case of cork, I would suggest using the floating cork floors over glue-down.

If you want to go for the best bang for your buck, look into Saso for engineered hardwood, Westhollow for Cork, and for Laminate try Quick Step, Pergo or Westhollow.

Q: I am expanding my kitchen and some part of the expansion will be over an open area underneath; therefore, I want to put in a heated floor, preferably electrical. I like the look of cork or bamboo floating floors. Can I put a heated system under these products?Gloria, Silver Springs, MD
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