Wood moves. That simple fact catches out more careful, well-meaning householders than almost any other DIY mistake I know. Planing a sticking door in summer feels like the obvious, logical solution, the door is stuck, you shave a little off, and suddenly it swings freely. Job done. But summer is precisely the worst moment to make a permanent fix to a wood door, and understanding why could save you a very draughty winter.
Key takeaways
- Wood absorbs moisture in summer and shrinks in winter—a 5mm movement is normal on a standard door
- Planing away clearance in July leaves gaps in December when the wood contracts back
- The 2mm rule: any more than that invites draughts when your door returns to its winter size
Why your door sticks in July (and breathes in December)
Timber is hygroscopic, meaning it absorbs and releases moisture from the surrounding air throughout the year. In the damp warmth of a British summer, the fibres in a solid wood door swell as they soak up atmospheric humidity. That swelling is what jams the door in its frame. Come autumn, the central heating fires up, indoor air dries out, and the wood contracts again, sometimes quite dramatically. A door that was grinding against its frame in July may rattle loosely in January without any intervention at all.
The degree of movement depends on the species of timber and how well the door was sealed when it was fitted. Oak moves considerably. Pine is a little less dramatic but still noticeable. A door that was painted on all six faces, top, bottom, and all four edges, when it was first hung will absorb moisture far more slowly, because the paint acts as a partial barrier. Many older doors were never painted on the top edge or the bottom, and those are precisely the ones that swell most severely each summer.
The gap I left behind
When I planed the edge of my sitting room door one muggy July, I took off what felt like a sensible amount, enough to give a finger’s width of clearance. By October, that clearance had widened to nearly half an inch. By December, I could feel cold air pushing through on a windy evening, and The Draught Excluder I wedged against the bottom of the door was doing nothing for the gap along the latch edge. I had, in effect, permanently resized the door for its summer measurements, forgetting that it would shrink back to something noticeably smaller once the heating came on.
The rule of thumb that joiners and carpenters work to is a clearance of around 2mm on each side of a door, enough to allow for seasonal movement without the door binding or leaving a gap large enough to feel. Planing more than that in summer risks creating exactly the situation I found myself in. The moisture content of timber in a centrally heated British home in winter typically sits between 8 and 10 percent, while in an unheated or humid summer environment it can rise to 14 or 15 percent. That difference in moisture content translates to real, measurable swelling and shrinkage across the width of a door — sometimes as much as 5 to 6mm on a standard 762mm wide door.
What to do instead (and how to fix the mistake)
The sensible approach, if your door is sticking badly enough that you simply cannot wait, is to plane the absolute minimum, just enough to allow the door to close without force, and then revisit the fit in winter. If the door still binds slightly in January, that is the correct time to take more off, because you will be planing to its driest, smallest dimensions and leaving the wood room to expand back toward the frame in summer without jamming again.
Marking the door first makes a real difference. Close it as far as it will go and draw a pencil line along the frame where it sticks. That shows you exactly where the problem sits. Many summer-stuck doors bind at the top of the latch edge, which is where timber movement is often greatest. A sharp hand plane, or a power planer used with considerable restraint, is far more controllable than sanding, which tends to remove material unevenly.
If you have already made my mistake and the winter draught is real, the fix is more involved. A timber fillet, glued and pinned to the latch edge, can build the door back out, though matching the existing timber and finish takes patience. A simpler short-term remedy is a draught-excluding brush strip fitted to the door stop (the thin strip of wood the door closes against), which effectively narrows the gap without touching the door itself. These are inexpensive and sold in most DIY sheds cut to length, though do measure the gap before you buy.
Repainting all six faces of the door once you have planed it is not optional, it is the step that most people skip. Bare timber on any edge will absorb moisture faster than a sealed surface, and the whole swelling cycle will be more dramatic the following summer. A coat of primer followed by two coats of eggshell on every edge slows the moisture exchange considerably and helps keep the door’s dimensions more stable year-round.
A detail worth knowing before winter arrives
Doors on the north side of a house tend to move more than those on south-facing walls, because north-facing timber sees less sun to dry it out and more persistent damp. If you have a notoriously difficult door that sticks every single July regardless of how it was planed the previous year, that orientation is worth considering, it may be that the doorway itself needs a proper drip mould above the frame to stop rainwater sitting against the timber, rather than needing a plane taken to it at all.