How come wood doors always grow bigger?

I'm talking about the typical situation where a wood door starting to stick in humid weather. I plane the door so that it no longer sticks in the jamb, and then everything is fine until a year later when it gets humid again and the door has expanded yet again and sticks.
I'm a woodworker, and fully aware of the effects of humidity expansion and contraction. I have an end-grain stick cut from the end of a tabletop I built that I measure it's length and use as a gauge to know where in the expansion and contraction cycle the environment is currently in. I always seal all 6 sides of the door in question to limit the magnitude of the expansion and contraction due to humidity.
The thing that I can't figure out is why do wood doors always only grow larger over time? I have numerous doors that I plane to fit very nicely, and then several years later I need to plane again because they have expanded larger. Never in my life have I ever seen a door that shrinks due to low humidity and causes an excessively large gap. I see this on both interior and exterior wood doors.
So what is it about the expansion/contraction cycle that appears to be biased toward expansion?
Ken
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On 8/22/2011 8:46 PM, Ken wrote:

What kind of door (construction, material (solid/veneer/mdf), etc., etc., )?
In solid doors I see the shrink/swell cycle regularly; I'd suspect something else going on other than just humidity changes...
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It only happens on my basement door. The basement is cooler than the upstairs living area. The living area gets humid. I don't have A/C. None of the other doors in the house swell/shrink.
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On Monday, August 22, 2011 11:53:27 PM UTC-4, dpb wrote:

These are all wood doors, but I see it happening on either solid wood doors (typically exterior) or veneer (interior with a solid glued-up core with veneer over that). This is in old houses from the 1920s, so there should have been plenty of time for the humidity expansion/contraction cycle to "settle out" into it's summer maximum and winter minimum range.
I didn't mention before that I'm in the Northeast US, so we have humid summers (and no A/C in the house), and cold winters with forced air heat. So I completely understand that there should be large swings in expansion and contraction due to humidity.
The thing is that the summer maximum seems to continuously increase and I have to keep planing doors. There is one interior door on the first floor (sits on a solid foundation, so there is little or no structural movement over time) that has expanded so much I needed to remove the mortised lockset, plane the strike side of the door about 3/16", cut the mortise deeper, and then reassemble everything. And that wasn't the first time that door had been planed. In that case I figured planing the strike side was easier than planing the hinge side and having to re-mortise two hinges.
The point to all this is that some doors have "grown" more than 1/4" in width since the house was built.
Ken
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On 8/23/2011 11:11 AM, Ken wrote:

Ken, Ya' got me...any chance of posting some pictures on one of the hosting sites?
In an earlier life did a lot of restoration on old Federal and earlier (some ante- many shortly postbellum) in the Lynchburg, VA, area, that is also quite humid in summer, relatively drier in winter but not, obviously, nearly as cold as the NE could be. I never ran across such an experience there even with the sometimes very large doors.
Currently in '10s-built farmhouse also w/ original solid frame and panel doors and there's never been such an observation, either. This is, of course, a much drier climate but far more extreme in temperature swings.
I'd suggest posting the question to rec.woodworking; there are some others there w/ lots of experience in your area plus some others in wet climates that might have some ideas; this being such an apparent change in width is not anything I've ever observed.
The thing is, long-grain doesn't expand/contract w/ moisture at all (in comparison as you obviously know) so all the change in dimension for a conventionally-constructed panel door has to come from the stiles which one would presume are only something like 6-8" each. The amount of dimension change over that distance that you're seeing is remarkable...
Any idea the species of the wood out of curiosity?
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On Tuesday, August 23, 2011 1:26:22 PM UTC-4, dpb wrote:

Yeah, that's why I'm amazed by all this. These are mostly rail and stile single panel doors, so the percentage across the stile width seems large.

Exterior doors are solid softwoods, don't know the species.
Interior doors are solid wood rails and stiles with plywood panels, and thick (3/32 - 1/8") gumwood veneer over everything. The solid wood is glued up miscellaneous hardwoods. On the top and bottom of the doors where there is no veneer, I can see 3-5 narrow sticks glued up to get the 6" width for the stiles. I can tell some of it is oak, but there are some other tight-grained hardwoods in there too that I can't identify.
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On 8/23/11 12:11 PM, Ken wrote:

(typically exterior) or veneer (interior with a solid glued-up core with veneer over that). This is in old houses from the 1920s, so there should have been plenty of time for the humidity expansion/contraction cycle to "settle out" into it's summer maximum and winter minimum range.

(and no A/C in the house), and cold winters with forced air heat. So I completely understand that there should be large swings in expansion and contraction due to humidity.

to keep planing doors. There is one interior door on the first floor (sits on a solid foundation, so there is little or no structural movement over time) that has expanded so much I needed to remove the mortised lockset, plane the strike side of the door about 3/16", cut the mortise deeper, and then reassemble everything. And that wasn't the first time that door had been planed. In that case I figured planing the strike side was easier than planing the hinge side and having to re-mortise two hinges.

My daughter's house in CT built 1955 has the same problem. Original hollow core (mahogany veneer over pine core) doors need planing/rasping every year for the 8 years they've been in house. Plus re-mortising at times
Can wood still "grow" after being cut, milled, etc ????
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On 8/23/2011 1:15 PM, Reed wrote: ...

W/ a slab door it's not so hard to imagine since the full width is all vertical grain for movement. Or, a composite interior could continue to swell some. But even there for it to continue year after year seems quite unusual.
No to the last question to anything other than movement owing to changing of properties owing to primarily moisture equilibrium changes and to a much lesser degree some temperature. "Real" wood growth diameter happens only on the outer surface at the cambium layer under the bark; the interior sap- and heartwood sections have already grown all they ever will once the year's spring and fall growth season are over the year they are produced; those never get any larger.
(Although there are instances of green lumber being harvested and sprouting new growth if left enough intact and in nurturing-enough conditions, mostly places like jungles, etc., that's not the case certainly w/ processed lumber such as is in a door that as well as being quite a long time removed from any living material still present has likely been through a dry-kiln as well...)
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On 8/22/2011 9:46 PM, Ken wrote:

humid weather. I plane the door so that it no longer sticks in the jamb, and then everything is fine until a year later when it gets humid again and the door has expanded yet again and sticks.

contraction. I have an end-grain stick cut from the end of a tabletop I built that I measure it's length and use as a gauge to know where in the expansion and contraction cycle the environment is currently in. I always seal all 6 sides of the door in question to limit the magnitude of the expansion and contraction due to humidity.

over time? I have numerous doors that I plane to fit very nicely, and then several years later I need to plane again because they have expanded larger. Never in my life have I ever seen a door that shrinks due to low humidity and causes an excessively large gap. I see this on both interior and exterior wood doors.

I always suspected minor house settling getting things out of square etc. But, now, thinking about it, the wood may actually continue to expand due to moisture uptake and drying cycles. I know this can happen with nylon parts.
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You've made a compelling argument for fiberglass doors...
Joe
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