Dear James: My house has wood siding, which I painted last year. Most of it looks good, but it blistered in some spots and is getting worse. What is the best way to repair it? —Dwight R. Dear Dwight: Blistering can look very bad and generally will get much worse and more widespread over time. Blistering is not just a symptom of improper application techniques; it often indicates some more serious problems with the siding or the wall behind it. You should definitely repair it soon. Persistent dampness in the wood siding itself is the most common cause of blistering paint. The paint film can hold itself together at first even if it does not adhere well to the wood, but over time and weather changes, it will bubble up. You may actually find some rotted wood under those spots. There are also some other application errors that can result …