Hardwood floor buckling from HVAC duct underneath


Lately I've noticed a problem in my living room floor in that the wood is buckling or crowning a bit with gaps between the boards directly above where there is an HVAC duct running underneath between the floor joists( about 10 feet length total). I think it has gotten worse this past year because recently I finished my basement and closed the ceiling with sheetrock, so I'm guessing all the heat from the duct is concentrated upward towards the floor, although I thought wood shrinks when its warm and dry instead of expand. Is there an easy fix for this? Can it be hammered down with a 2X4 and hammer?
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You are quite right about how wood dries and shrinks. So obviously, what is happening to your flooring is not dry heat related, but moist heat related. The fact that it is in a basement is a clue. Basements are notorious sources of moisture. Somehow in your closure of the duct area you have a moisture source. Could be leaky pipes, damp walls allowing an upward drift of moisture to the ceiling area. Whatever, a thorough look at the way the basement was finished is in order. Once a most likely cause is noted, remedial action is next. It would not be surprising to find that code violations were the cause. Good practice in basement upgrades mean insulation plus vapor barrier (6 mil poly film most places) just for starters. Do some research and talk to city building code folks to get the skinny. Look at local construction projects to get a feel for how pros do it.

Probably not. The subfloor sounds like it is damaged. Maybe it might revert somewhat if it dried out. Not a happy situation.
Joe
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Mikepier wrote:

Hi, IMO, it's either problem with sub floor or poor installation of HW flooring. (no room (gap) for expansion)
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Is there an easy fix for this? Can it be hammered down with a 2X4 and hammer?
Vent the basement cieling and sand the floor back to level. Just a thought.
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Mikepier wrote:

An uneducated guess would be that the wood floor expands due to the heat and insufficient room left around the flooring for expansion. Wood furniture, usually with some unfinished surface, expands and contracts because it can absorb moisture from air. Without a moisture difference, there is still some movement with sufficient temp change. Since you associate the crowning with closing up the heat duct, seems the answer lies either in opening ceiling and insulating duct, or ripping up baseboards and adjusting perimeter of flooring. Got some pix? How much above the level flooring does the crowning go?
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Is the duct fitted tight against the above floor is it insulated, I dont think hammering will do anything, maybe finish nails or counter sink screws and cover the screws with plugs. I would lower the duct and see what happens
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Duct is about 8X5 rigid, and its insulated, its pretty much almost up against the floor. Thers no way to lower the duct because the floor joists are 2X8's, so the duct would sit lower than the ceiling. I use forced hot air, no humidifier in the house , basement is dry, whole house is dry, so I don't think it's humidity or moisture related.
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Does your hvac system have a humidifier in it? If so and the metal boot ends at the subfloor then you may have moist air infiltrating the floor area. Enclosing the space below may have kept the air in closer proximity to the wood for longer. But enclosing the space below may just be a coincidence. You can use hvac mastic to seal any gaps. You might be able to raise the metal boot as well. If you don't have a humidifier then I'm a bit surprised.
In most cases crowning at the joints is caused by moisture. I would not expect heat alone to do anything. Typically in the winter wood floors shrink and have more pronounced gaps. Unfortunately after it drys the crowning may remain. Unless it is really bad you probably just want to live with. The only fix is to sand the floor flat again with a belt sander and refinish.
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The area was always a little crowned, but it seems more pronounced this year. Perhaps maybe the enclosed space underneath is trapping cold air when the heat is not on, maybe from the basement sill plates. Just a guess. I am going to try and keep the area in the sun by opening up the front window blinds to see if it helps dry it out.
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Hello,
Put a room dehumidifier under the area; if it runs and collects water, you need a dehumidifier in your basement. Obviously youarenot boss, your house its boss over you . . .
Another thingy: whatis wrong with having the vent hang an inch or two past the ceiling rafters? If anyone says anything about it: just say you wanted a touch of Danish Modern in your house to see if you like it . . . or get a different size/type vent. If your furnace doesnot get proper air, youwill blow out your internal thermostat. Then pile all your furnature on the hump until the weight forces the area flat. If anyone says anthing about it: tell them you want a touch of Early Nordic in your house to see if you like it . . .
Truly
Truth will set you free, according to Jesus in John 8:32
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