Why Colorado’s Dry Air Cracks Your Trim (and What to Do About It)

What happens

Wood absorbs and releases moisture with the air. A heated Denver house in January can sit at 15 percent relative humidity. Wood installed at 40 percent shrinks across its width as it dries out. A ten-inch-wide board can lose an eighth of an inch. Joints open, caulk lines crack, and floors show hairline gaps.

Acclimate first

Material should sit inside the house, unwrapped, for at least a week before it is cut. Flooring and stair treads, two weeks. This one step prevents most of the gaps clients see.

Choose stable species and cuts

White oak, walnut and cedar move less than red oak, hickory or pine. Rift and quartersawn boards move less than plain-sawn. Plywood does not move across its width at all, which is why cabinet boxes and built-in carcasses are plywood.

Build for movement

Wide panels float in their frames instead of being glued. Trim is fastened so it can move a hair. Inside corners are caulked with a flexible sealant, not a rigid filler. Floating shelves ride on steel that does not care about humidity.

Run a humidifier

A whole-house humidifier set to 30 to 40 percent is the single best thing you can do for wood in a Colorado home, and for your sinuses. Luke will say so on every walkthrough.

Expect one touch-up

On painted work, one round of caulk touch-up after the first winter is normal and is part of the job. After that, the wood has found its range.