We have an addition on a crawl space. The crawl space is about 3'
high. Underneath on the ground is rock dust with plastic sheeting over
top. The spaces between the joists are insulated.
We had hardwood flooring put in the addition. Within about 6months the
planks are cupping. It's very slight but it is noticable (at least to
me). What is causing this? Everyone I've asked always says "is their
plastic underneath covering the rock?" the answer is Yes. Then they
don't have any other ideas.
Does anyone out there have any idea what caused this? The worst
cupping is going on in the entry part of the new addition. There's a 6
foot opening to walk through. The flooring right in this obvious area
is the most noticeable. Most of the room is covered with an area rug.
What's under the area rug looks ok.
Where do you live? Do you use your air conditioner? Regardless of the
plastic under the crawlspace, is it moist under there? Was the floor nailed
down or glued down?
My parents are struggling with a similar problem with a new hardwood floor.
Their crawlspace is bone dry. The flooring installer and the manufacturers
rep both blamed crawlspace moisture, which seems to be their attempt to
dodge the problem. Personally, I believe the installer goofed (he glued the
floor down, which is completely against anything the manufacturer
recommends). A bad situation which may need to be settled in court...
On Sun, 22 Oct 2006 23:10:06 -0400, "Kyle Boatright"
Below is a partial quote from a website describing the same problems
you are. Hope it helps.
Is this a solid wood product or an engineered product? Solid planks
will expand and contract more than an engineered product. Four-inch
planks will expand and contract more than smaller planks, and parquet
flooring rarely has these problems because it is made of many small
pieces of wood.
When an installation occurs, most installers check the sub floor for
moisture content. They will not install a product if the level of
moisture is too high. A solid wood floor is almost always installed
with a moisture barrier between the sub floor and the flooring to help
control moisture emission.
Sealing and sanding could also be a factor. If a floor is too dry when
installed unfinished, or too damp and the climate changes, the floor
will cup or peak, the opposite of what it was at time of installation.
Wood floors are a living product which have capillaries that carry
moisture throughout the planks. Moisture emissions from cooking,
showering, carpet cleaning, and water damage are all factors, which
could cause a floor to cup or peak.
Most floors do change in their appearance as the seasons change.
Humidity in the summer is much less then the fall. In climates that
have a lot of snow, like Minnesota, the humidity in the winter may
drop so low, wood may split and dry out. This is where the use of a
humidifier to add moisture to the air could be beneficial.
Floors/boards cup for one reason, a differential in moisture content on
The drier side will be the concave, the wetter, convex.
What you are seeing is the results of this simple fact, but mitigating it
may not be that simple, and much depends upon your climate.
The obvious solution is to insure that both sides are subject to the same
relative moisture/humidity levels and you need to think along that line for
finding a solution.
Something as simple as moving air in the crawlspace (fan ventilation) may
help, or you may need to humidify/dehumidify one side or the other, or both.
... or you may need to learn to live with it on a seasonal basis. Some of
the finest OLD houses in the world exhibit this behavior at certain times of
the year, particularly in areas where/when there is a marked change in the
Another possibility would be a water leak. We had a leak at an
outside door and there was a lot of cupping in the area, and then a
big ol hump, but it would be more isolated to a smaller area rather
than the whole room.
I think you should have a moisture barrier between the flooring
and the insulation. That will keep the humidity and temperature
on both sides of the flooring approximately equal.
That may be the case already, but you didn't say.
If the flooring is concave up, then the air in the room is drier than
the air in the crawlspace and vice versa.
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