Doors sticking: foundation problem or humidity?
Most sticking doors in Tennessee are seasonal humidity, not foundation movement. The distinguishing test is whether the door frame is still square — humidity swells the door, movement racks the frame.
A sticking door is one of the most-cited foundation warning signs, and in Tennessee most sticking doors are not a foundation problem at all.
They are wood doing what wood does in a humid climate. Knowing which you have takes about twenty minutes and saves some people several thousand dollars.
The gap test — the one that actually decides it
Close the door most of the way and look at the gap between the door edge and the frame, all the way round.
Even gap, narrowed all round → the door has grown. That is humidity. Wood absorbs moisture from the air and expands across the grain, which is why it is the latch edge that binds first.
Wedge-shaped gap — tight at one corner, wide at the diagonally opposite corner → the frame is out of square. Something structural moved.
That distinction is the whole diagnosis. Everything below either confirms it or tells you where to look next.
The full checklist
| Test | Humidity | Structural movement |
|---|---|---|
| Gap around the door | Even, narrowed | Wedge-shaped, diagonal |
| Which doors | Scattered across the house | Clustered in one area |
| Timing | Seasonal, returns each summer | Progressive, does not recover |
| Improves in winter? | Yes, noticeably | No |
| Floor level nearby | Level | Sloping |
| Cracks above the door corner | None, or hairline | Diagonal, widening |
| Vinyl windows affected? | No | Possibly |
| Latch alignment | Latch still meets the strike | Latch sits above or below the strike |
That last row is a good confirmatory check. Humidity makes a door tight but the latch still lines up with the plate. Movement shifts the latch relative to the strike — you can see it misaligned with the door open.
Why Tennessee makes this so common
Tennessee summers are genuinely humid, and interior humidity tracks it in houses that are not running air conditioning continuously.
Solid wood doors and wooden window sashes respond directly. Add a crawl space running at high relative humidity beneath the floor — feeding moist air upward through the stack effect — and interior wood sees a bigger seasonal swing than the outdoor climate alone would produce.
Which produces a genuinely useful corollary: if your doors stick every summer and your crawl space humidity is high, the crawl space may be the cause of the sticking doors. Controlling crawl space humidity has fixed more sticking doors in this state than foundation work has.
Do this before calling anyone
- Note the date and the season. Seriously — write it down. In six months you will want to know whether it improved.
- Test every door in the house, not just the annoying one. Map which stick and where they are.
- Check the gap shape on each, as above.
- Put a hygrometer in the crawl space for a week. Over 60% relative humidity makes humidity a strong candidate.
- Check the floor with a level near the affected doors.
- Look above the door corners for diagonal cracking.
- Wait a season if everything points to humidity. The cheapest diagnostic test available is time.
What each answer costs to fix
If it is humidity: a crawl space dehumidifier at roughly $1,200–$2,500 installed, or encapsulation at $5,500–$15,000 if there is more going on down there. Both address the actual cause. Planing doors is $0 and treats the symptom — reasonable on an interior door you do not care about, wrong on a solid exterior door you will want to re-hang in winter.
If it is structural: you are in foundation territory, and the next step is an engineer rather than a carpenter. Do not adjust the doors first; the engineer wants to see the building as it is.
The mistake worth avoiding
Planing or re-hanging a door before you know the cause destroys your evidence and can leave you with a door that does not close in January. If a door is hard to use right now, take the photographs and the measurements first, then adjust it. Five minutes of documentation preserves the diagnosis.
Common questions
How do I tell the difference quickly?
Check whether the gap around the door is even. Humidity swells the door itself, so the gap narrows evenly all round. Foundation movement racks the frame out of square, so the gap goes wedge-shaped — tight at one corner, wide at the diagonally opposite one.
Does it matter which doors stick?
Considerably. Several doors in one area of the house points to a structural cause under that area. Doors scattered across the whole house, all at the same time of year, points to humidity.
Should I plane the door?
Not until you know why. Plane a door that swelled in July and it will not latch in January. Plane a door that moved because the floor dropped and you have removed the evidence.
Why do windows do it too?
Same reasons. Wooden sashes swell with humidity, and window openings rack when a wall moves. Vinyl and aluminium windows do not swell meaningfully, so a sticking vinyl window is more likely structural.
How fast does foundation movement happen?
Usually slowly — over seasons and years. A door that worked in spring and does not in August is far more likely humidity. A door that got progressively worse over two years is more likely movement.