Problems With Maple Flooring Over Radiant Heat
SCoastCarp
| Posted in Construction Techniques on
We are repairing a vacation home on the beach with hydronic radiant heat under the subfloor and maple hardwood above. The radiant system is Pex lines snapped into aluminum plate diffusers that are attached to the bottom of the subfloor. Something has caused the maple floors to cup throughout the house. Does anyone have experience with this? We don’t have big temperature changes in this area and the humidity seemed ok. I read that maple is not recommended over radiant, but I haven’t found out why that is. Any advice ?
Replies
i am assuming because you have your plates set on the bottom of the sub floor this is a retro fit system. Was the flooring pre finished or unfinished? I ask because most likely if it was prefinished it was not quartersawn. this does affect the amount of movement considerablly.
I have never seen a system with mapel, but i would think this would be a poor choice for this kink of system. have seen it with some oaks but mostly walnuts and cherry.
depending on the amount of buckeling you may be able to refinish,,,
This system was put in when the house was new and the flooring installed was unfinished maple. We thought heat might be the problem - the boiler temperture was 130 degrees. We are going to suggest to the owner to turn the heat down ( around 100) and see if this helps. Then, we may try to refinish later.
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Which way did it cup? Concave up or down? Did this happen right away or later?Is the flooring solid maple or an engineered floor?
The wood boards cupped up at the edges, they are solid maple and according to the owner the problem started a few years after they built the house.
If the boards cupped up at the edges it's because the boards are drier on top than on the bottom. This is probably due to a combo of fairly dry air inside the house and a damp crawl. If there is little insulation below the heaters that would exacerbate things because the heat would evaporate moisture from the floor of the crawl, making it that much more humid.
This is the most common type of cupping. It would indicate that the moisture content is higher at the bottom of the thickness of the flooring than at the surface. This can be caused by excessive moisture migrating somehow from below. LIke I said, moisture always moves from wet to dry. Finished sides of flooring generally stay drier as they usually are the film sealed side and are exposed to the typically drier, more conditioned air mass. Alternatively, the upward edge cupping could be the result of boards swellling throughout the thickness (higher moisture content) and subsequent hydraulic stress caused material deformation at the edges. The latter is unlikely unless the wall edges are highly restrained and individual boards are well bonded to the substrate. Usually areas of the floor will "dome up" (before severe edge cupping) from overall moisture content changes. In structural terms, this materials way of "moving away" from the stress. Sometimes doming is not too obvious, but hollow sounds can be detected while walking or tapping on the floor.
Moisture contents changes are generally the result of higher sustained releative humidity levels than when material was manufactured and finished. You may want to investigate the acutall moisture content of boards and substrate(s) with a moisture meter. Levels above the 5-8% range can be suspect. I have fouind most flooring is delivered and/or packaged in the 5-6% range.
captain obvious strikes again!!!
deadnuts wrote:
LIke I said, moisture always moves from wet to dry.
quarter, rift or plain sawn has a lot to do with the tolerance a finished floor has to the changes that occur with hydronic heating. maple is soft in comparison to the types of wood that are commonly installed over hydronic heating which makes it that much more vulnerable to the problems seen by the op.
Numbnuts, you clearly know very little (aside from what you read on houzz HAHAHA) about the matter. hydronic heating is the cause of the cupping, bet you 5 glazed, 5 eclairs, and 2 boston creams...u clown.
A few years?
I wonder what made floor cup after a few years. A heat or moisture problem should have happened within one weather cycle(year). Could there have been another event besides HVAC? Could the field finish have been a quality question? I do think130degrees is too hot unless the are heating domestic water too. Yes, wood will expand and cup without the presence of moisture (too much or not). Unfinished wood does usually comes more moist than finished, but again, if it took years to happen it may have been a different problem altogether.
really?
MYBuilder wrote:
Yes, wood will expand and cup without the presence of moisture (too much or not).
No, it won't. At least not to any degree that we, as end users, can measure. In fact, the Wood Handbook, which some (other than I) refer to as "the bible of wood information", states the expansion across the grain is .00002 per degree F for bone dry wood.
If you'd like to back up your claim above as something other than idle jibberish, MYBuilder, then by all means please do so.
Any wood, if it's heated on one side and not the other, will cup. This is due to the fact that the heat dries out one side more than the other. Soft woods will generally be worse than hardwoods, and solid wood worse than "manufactured". Flat sawn wood will be worse than quartersawn. (The direction of the cupping can go either way, depending on several variables. Normally it would cup with the middle of the plank raised and the edges turned down, but if the crawl is fairly damp it could go the other way.)
Normally one can expect the effect to stabilize and reverse somewhat after the heat's been on for awhile, and largely reverse itself when the heat's turned off (though it may take some time). But you will have much the same cycle the next heating season.
The important variable is moisture content,
not heat.
Wood changes dimensionally due to changes in moisture content. Period. To confuse the issue by interjecting the notion that wood changes dimensionally based on the introduction of heat only proves ignorance of one of mans most basic and useful building materials.
In order to prove the fallacy of Dan's hypothesis one only has to understand that heat energy moves by conduction, convection, and radiation. Wood doesn't really care about any of those variables when it comes its movement. The moisture within the wood cares*, but the wood itself does not. Thus I can pour scalding water on one side of a board (introduction of heat) and have it cup one way or I can expose the same side of the board to a close proximity infrared radiant space heater (introduction of heat) and have the board cup the other way. In both cases heat was introduced, but the effective result was very different. I can also make a board cup in different directions by coordinated introduction of moisture alone-regardless of any change in temperature. Thus, the key variable that matters here is change in moisture content, not exposure to heat.
*Moisture moves from wet to dry. Always.
Do your customers know?
Anything heated will expand. Steel, glass, plastic, wood. When wood is heated, since the density varies throughout the piece, the wood will not just expand, it will.... Wait for it... Cup, twist, crook, or bow. Regardless of the presence of H2O. H2O will also cause...Yep...Cup, twist, crook, or bow. Regardless of the temperature. I don't know why we still use wood. Probably because we want to hear what deadnuts wants to comment next.
This flooring was installed on the second floor of the house. We checked the humidity in the boards and it was 8 %, so we don't think moisture was a problem. The temperature in the house varied from 60 when owners were gone to 68 when they were there. We did find that the water leaving the boiler was 130 degrees and think this may be the problem. We are hoping to lower the boiler temperature to around 100 degrees and see if this makes a difference. Then possibly sand and refinish the floor later.
If this cupping seems to be relatively static -- not varying with the season -- then I would begin to suspect that it has more to do with how the wood was cured and finished than with the radiant heat.
If it's still changing with the seasons I'd suspect that the bottom floor has significantly higher humidity than the top floor.
Again, it doesn't have anything to do with how the wood was cured and finished. I would bet dollars to donuts that it was milled and finished perfectly flat.
It rather has to do with the moisture content changes that have occured since it was manufactured and moved into it's current service environment.
There is the minor point that the type of subfloor could have something to do with it. I suspect that some "particle board" type products are hydroscopic and would tend to keep the bottom side of the flooring wetter.
First of all, wood is checked for moisture content, not relative humidity. If you're a flooring installer, you may want to educate yourself on the basics of your craft.
Second, you'd have to know the installed moisture content of the flooring to know whether the current moisture is a problem or not. The 8% alone means very little.
Third, it depends on how you checked for moisture content... and where. The substrate M.C. is also relevant. What is that?
Fact check
deadnuts wrote:
As for rift sawn lumber: That's a venner cut, Mark.
you get that from the house wives on Houzz... you cant be serious.
the cut makes an incredible difference how reacts to hydronic heating, so does its width.
whatever meds you were on this winter worked, you should get back on them.
you think he has a leak??? do you not think (however hard that may be for you) that the leak would be evident on the first floor ceiling?
here's your incredible difference
mark122 wrote:
deadnuts wrote:
As for rift sawn lumber: That's a venner cut, Mark.
the cut makes an incredible difference how reacts to hydronic heating, so does its width.
Wow. "incredible difference", huh? Not only are we getting the usual misinformation from you, but we're getting it with a dose of drama. What's the matter, aren't you getting enough drama with your daytime soaps?
Actually, it doesn't make any difference at all. Wood in service does not react to heat; it only reacts to changes in moisture content. Period.
Your faulty logic is the same folks use when claiming that warm air holds more moisture than cold air. Go ahead. Challenge that.
Be very, very careful what you put into that head,
because you will never, ever get it out.
Thomas Cardinal Wolsey (1471-1530)