Fit Trim Flat to a Wavy Wall With Relief Cuts on the Back

The Problem

Walls are rarely flat, and stiff trim stock bridges the hollows — leaving gaps behind the board that caulk has to swallow. On a board-and-batten wall, where battens and rail have to meet flush, one bowed section telegraphs through the whole layout.

The Technique

Cut a series of shallow relief cuts across the back face of the board — partway through its thickness, leaving the front face intact. Each kerf removes a little of the board's stiffness, and the board bends to follow the wall's contour when it's fastened. The show face stays unbroken; the flexibility lives entirely in the back.

The reel shows it on a stairwell board-and-batten install, where the transition pieces needed to sit level with each other against a wall with some wander in it.