info on solid wood flooring over radiant
badarse
| Posted in Construction Techniques on
I am planning a to put solid wood strip flooring over a rasied lightweight slab sandwiched between the subfloor and another piece of plywood. What do I need to know? Any info would be appreciated.
Replies
If I understand you correctly, you have radiant heat tubing embedded in a lightweight concrete slab atop a floor structure (likely a 1.5 layer of gypcrete), and then a layer of plywood on top of the slab.
Correct?
Then you want to lay wood strip flooring, 3/4" solid, not "engineered," on top of your plywood.
Correct?
If this is what is going on, and you need to know some things, here is some info for you.
There are species that are OK atop radiant heat, and species that are not OK. Good performers are oak and black cherry (that is domestic cherry, not a rain forest species.) The wood flooring institute has info at their website on species.
It is best to use a narrow strip width atop radiant heat. I like to stay down at or below 3 inches.
It is also best to use quartersawn wood. Worst case for me would be to specify quarter and some mix of rift/quarter.
One last thing, and it regards your ply atop the slab. It should be well-fastened to its substrate, and 3/4" thick. That thickness will ensure good nailing for the finished flooring.
How do you nail the subfloor without putting holes in the tubing?
blue
My flooring guy would use an L-nail flooring cleat at 1-3/4" length.
You also need to know that your floor is going to be very unresponsive to calls for heat. That is a lot of wood to put between the heat source and the room.
It is good that you at least have a thermal mass that you can heat up. If you had Warmboard or something like that installed, you would have to keep the circuit running almost constantly.
BTW, You didn't say if the gypcrete was already installed. If not, you may consider 2x2 sleepers and have the gypcrete poured between them and eliminate the second layer of plywood. If you go that route, I would keep the spacing to no more than 10", so you have sufficient nailing for the hardwood.
Personally, I would install a floating floor in your situation. They have some good ones that you can't tell from strip flooring.
Edited 11/16/2006 7:57 am ET by BoJangles
You want the circuits running constantly, with or without mass. That's the key to the promised land of ultimate comfort and efficiency ;)I too would recommend a floating floor. Two layers of wood is a lot, and using sleepers isn't so great as after the 'crete dries, it shrinks and you lose conduction if the wood is nailed to the top of sleepers.Problems with wood over radiant are based on two factors, primarily:1. how hot will the floor be? This depends on your heat load
2. What is the moisture content of the wood? this is important with any wood floor install, but even moreso when the floor itself is heated. it must be installed at an appropriate moisture content for your region.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
You want the circuits running constantly, with or without mass. That's the key to the promised land of ultimate comfort and efficiency ;)
That's true...however I feel better (mentally) if only my wood boiler is running constantly ;)
It would be of interest to a lot of people if you went over your strategy for keeping a heating circuit running constantly. It is a fine line between providing the right input in relation to the heat loss of an area.
well just because you run the circuit constantly doesn't mean the heat source runs constantly... though, if you are using a modulating heat source, that is exactly what you want it to do, it just modulates how much it fires with how much heat you need.There are currently two ways to achieve true constant circulation:You can control the water temperature with a mixing device that is tied to a sensor in the space you are heating: you have constant circulation, and the system modulates the water temperature to whatever is needed to maintain the room temp. However, this only works for one "zone". So if you have multiple zones, doing this is very, very expensive and complex. You can also control FLOW, such as Thermostatic Radiator Valves, which choke flow to a radiator as a room heats up. There are items that do that for radiant as well, but they have their own limitations and I have not used them yet.. I'm concerned about very large temperature drops across a loop making floors noticeably different in temperature. In this flow control case, you have a constant circulation header (usually tied to an outdoor sensor to modulate its water temperature), and then each emitter controls its own flow with the TRV or similar device.In the vast majority of cases though, you have multiple zones, and a budget. So you can approximate constant circulation cheaply this way:-Modulate temperature using an outdoor sensor tied to a modulating boiler, or to a mixing device. This gets your water temperature close, if not exactly, to what is needed for the rooms.
-Try to keep water temperature requirements across the system as close as you can, so you minimize one zone setting a high water temperature requirement that will make the rest of the zones shut off more often.
-Finally, use a good thermostat with Pulse Width Modulation to provide for the most even cycling action you can.If you do these things well, you can get pretty close to constant circulation in a lot of cases.Note that your heat source firing is independant of your radiant circulation; with these methods you only turn on a boiler when you need an injection of more heat into the circuits. Or, with a modulating boiler, it ramps down its output to meet the load, so on-time is not the measure of fuel usage you are worried about.Weee!-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
I have a white oak floor over gypcrete with imbeded radiant. I used 2x4 sleepers (flat) on 16 inch centers to lie over my joists. I didn't see any point in making the sleepers closer because then they wouldn't bear directly over the joists. Granted, I have lost some holding ability for the flooring attachment, so I used some poly adhesive on every-other board. It's been two years since installation and all is well. My gyp guy took a great deal of care in filling between the sleepers, adding a bit overfill to allow for shrinkage. In fact, I had to grind down a few spots where he miscalculated. I don't have constant wood to gyp contact, so the convective transfer is slowed a bit from the ideal situation of them touching everywhere. But, I don't believe that is really attainable in the real world anyway.I was encouraged to place the plywood layer on top of the gyp by the flooring guy who advised me, to aid the nailing only. That would have made for an easier flooring install, but would sacrifice heat transfer, so I didn't do it and opted for the sleepers.All in all, I am very happy with my floor.
badarse,
I think (pure speculation) that you are worried about the thermal effects of heat. maybe you worry that if you heat up the building it will open the wood joints?
relax. wood expands and contrtacts based on moisture not tempurature.. metal expands and contracts on tempurature.
If you have brass inlayed you might notice a tiny ridge form with the rise in tempurature, noticable maybe but not serious..