Humidity and wood indoors

Wood indoors spends the year following the air: drinking the damp of summer, giving it back to a heated winter room. The job of the householder is not to stop that exchange, it cannot be stopped, but to keep the swing inside the band where nothing cracks and nothing mildews.

The comfort band

Between roughly thirty-five and fifty-five percent relative humidity, wood in a temperate house moves within safe limits. Below thirty, boards shrink and joints open; above sixty, the timber swells and the margins where moisture never dries, sills, sash pockets, the space behind furniture on an outside wall, become the places mould starts. A cheap hygrometer is the only instrument this advice needs; the file keeps one at eye level and believes it.

The signs of a dry house

A dry winter house announces itself in the wood: floorboards gap at the seams, a drawer that ran smoothly in August now runs loose, a tabletop shows a faint white crackling in the finish where the board shrank under it. These are the calls of thirst, the wood asking for the moisture the heating stole. They are not emergencies; they are the season speaking.

The signs of a wet one

A wet house answers differently: windows that weep at the edges, a sweet musty smell in a closed room, drawers that stick, a bloom of grey at a corner skirting. The answer is the reverse of the dry house, not to add moisture but to take it out: ventilation first, a dehumidifier where the air cannot be moved, and the drying of wet habits like indoor laundry in a sealed room.

Where the wood is most at risk

The risk lives at the boundaries: behind furniture against an outside wall, inside unventilated closets, under rugs on a slab, in the basement and the sill plate. Move the air at those places, even passively, and the wood keeps itself.

The house as a slow instrument

A timber house is itself the hygrometer: the gap at a floorboard seam, the fit of a drawer, the rattle of a window in its track are all readings, taken for free, every day. The instrument is slower and less precise than a dial, but it never runs out of battery, and a reader who learns it knows what the air is doing to the wood before the wood has to protest. That is the whole of the care this card asks for: watch the seams, and the seams will tell you.

The seasons of a timber room

The file keeps the band in mind through the year: spring and autumn take care of themselves, summer asks for ventilation and a watch on the corners, and the heated winter is the season to watch the seams. Where the house runs dry for months, a bowl of water on a stove or a well-placed humidifier buys the wood its margin; where it runs wet, moving air is always the first answer and a dehumidifier the second. The band is a range, not a target, and the wood forgives the swing inside it.

The card, filed

Wood indoors wants the same thing the people want: air that is neither parched nor damp, and a place at the edges where moisture can leave. Read the hygrometer, open the closet, watch the corners, the house will tell you which side of the band it is on.