Wide Plank Floor Over Radiant Hydronic Heat:
My wife and I are building a new house. We have about 2,000 BF of newly milled, green, beautiful elm as wide as 24 inches and expect it to yield at least 1,000 SF of wide plank flooring in the 10-12 inch range. We expect a year of air-drying to about 12-15% moisture content and then will probably have it kiln dried the rest of the way. Then I’d mill it, put in anti-cup grooves on the bottom, mill in tongues and grooves, and install it over 3/4 in T&G plywood subfloor by top-screwing and plugging the holes with matching elm plugs (I may use some contrasting plugs around the perimeter as a design add-on). There will probably be some movement, we understand, especially in Seattle, where the winter humidity is about 90% and summer about 50%. Since it will be new construiction there’s no way to truly let the wood condition a final few weeks in the heated house, since I am not sure if the house will be heated, what time of year it will be, etc. How many screws do you put across the face of a a 12-inch board? One, trusting the T&G to hold the rest, and allow for freedom of expansion? Two or Three? I am prepared to put fat baseboards all around with some base shoe so there’s a good inch+ in each direction for expansion and contraction, but is that logical if there are multiple screws holding the boards down?
I also want hydronic radiant heat under the floor–my architect says “Probably not!” because of the expansion/contraction issues, but another architect (albeit not one I’m paying) says that new hydronic systems are much cooler than the old ones and the heat/cold extremes are much more subtle and movement will hardly be an issue.
I want a refined look without a lot of gaps in summer
I’m sure my builder won’t guarantee the floor, which is a risk I am willing to take if I can foresee all the potential problems and take preventive steps now.
Does anyone have any suggestions for how to best approach this, or what books/online sources might have good advice?
Thanks in advance,
Bob Mangino, Seattle
Replies
bob- talk to local flooring guys/suppliers about wide plank flooring> over radiant & your damp location never worked w elm, will happen eventually as the chinese are shipping it over here when we lay wide plank floors in damp areas, a trick is to install steel washers on edge between courses as they are being nailed up might sound like overkill, but it expands tight w humidity spikes see what the local guys are doing
we nail the t&g edges w flooring guns 5" and wider also gets glued w lines of pl400 do floor perimeter as you described, fasteners won't stop expansion the screws will help hold, more of a good appearance than the number of screws used ...bigger plugs will look better on planks choose the size and drylay some on planks placed on subfloor to get pattern that you like
supposed to use very stable product over radiant, like rift & quarter sawn oak, but i've installed other species and wider than normal sizes w/o problems check w your heating guy if architect is right all my jobs were nailed direct to subfloor, no sleepers... pex lines were under subfloor in clips you need to acclimate that stock in the work area, split it up between floors of installation if more than one... moisture readings will differ between 1st & 2nd flrs
ed2,
Thanks a ton. When you note the steel washers, do you leave them IN there, or use them as spacers, nail the floor, and pull up the washers (leaving a gap of about 1/16th inch between boards)? I also like the idea of putting out a pattern of varying widths and plugs ahead of time to get an idea of what it will look like. And you're right, the half inch plugs I was imagining would look puny and like little mistakes/dots in 12 inch boards.
I figure that in the year-plus that the lumber is drying I'll talk to a handful of flooring installers and suppliers, as well as a few heating contractors. The architects are no dummies, but I am not sure how practical their knowledge of these items are other than to say "well, you want to be careful wit that," or "discuss it with your contractor."
Thanks again!
-Bob
steel washers set on edge as temporary spacers as new course gets installed, hold loose enough to set washers in seam, rest on tongue keep nailing courses w washers in place and adding them to the new rows of flooring after a few courses of wide planks are in, start pulling washers from earlier rows creates expansion space, gets depleted w spring/summer humidity
use a humidifier during heating season to put water into house, monitor w humidity meter cheap ones at walmart, etc if two floors, humidifier and meter ea floor they have furnace "duct-mounted" units that work when fan is on independent units seem to work better acclimate in work areas after drywall taping/ wall primer paint is dry i'd go 2-3 weeks minimum w big stock like that, crib stack or stickers *still best to talk to locals, have a lot of wet in seattle if install is during wet season, might tell you to skip spacers
I'm going to be building a new house and am interested in rhf in teh basement. Can someone point out a good site to learn more about this. My goal is to finish the basement totally (well...maybe not finish the drywall) myself so i'd like to understand how tough this rhf is to design/layout and how expsensive it is.
Sized properly, the temperature of the floor should never need to go above 87 degrees with RFH. With outdoor reset in your mild climate, it would usually be much cooler. Same temps the floor would see on a summer day. Unlikely to cause any additional problems.
Though, with wide planks you have to expect gaps, and learn to love them. Charming, right?
Our oak hardwood flooring is not affected by the radiant floor heat in our home.
The strips are only 3 1/4 " wide I see some small seasonal changes in the flooring, but the last house without radiant with same flooring behaved the same way. If your rfh is working properly it does not overheat the flooring. By nature wide boards will show more movement but the heat should not contribute to shrinkage.
>I want a refined look without a lot of gaps in summer
Wouldn't gaps appear in winter, not summer?
How tight a range do you think you'll get on interior humidity? I'd think that affects expansion/contraction of anything in the house more than the heating method. In the buildings I do, we keep humidity in really tight ranges, and don't see any seasonal changes in floor, doors, windows, furnishings. But in a house with less tightness, the variations would be enough to cause doors to stick, furniture to loosen, gaps to develop.
The heat I run through my tubes makes the floor no warmer than the sunshine on the floor all day. But the specs were for 125 degree water...we just don't do that.
I'd see what the specs on the RFH would be, and I'd make a determination on the seasonal range of interior humidity, be/f I determined if I'd have a problem with wide planks. A friend has wide planks without RFH, and their gaps grow from 0 to about 1/4" throughout the year. That'd be unacceptable for me.
Thanks, all, for the sage suggestions. The mild Seattle climate, I had forgotten, does mean that we have more moderate heating needs and the water in the tubing can be pretty lukewarm. One architect told me his water was about 85-90 degrees and the other said "Really? That sounds okay." So it looks like this is doable.
I'd like to minimize gaps though I know they will occur. And in this climate, no matter how tight a house is, it's the winter that's humid (6 months of drizzle and 50 degree temps are not cold enough to make it New England dry in the winter, plus three little boys running in and out--at times it feels as if you're wearing a wet shirt and you haven't been outside all day!), so that's when the floor swells. (right?) The summers are the bone-dry times, sunshine and 75 degrees for two straight months without a cloud in the sky (but shhh, don't tell anyone, they think Seattle's gloomy year-round). So that's when the floor wold shrink, I assume.
Hey, if the mild added heat to the floor drives out some of the moisture in winter, it might limit seasonal movement. Time to talk to the locals and see what they do.