Can You Hammer the Plaster Around a Window to Make Wood Trim Fit?

Surface Damage

• Plaster is stronger than joint compound, but neither can withstand much hammering. Plaster will crack and chip. Joint compound is more likely to develop gouges and dents. With either type of surface, you never know when a huge piece will break off. In other words, the damage you create might spread farther than the wood trim you’re installing, meaning you can’t hide the problems. You can repair damaged plaster or joint compound by coating the area with several coats of joint compound and smoothing the area with 150-grit sandpaper after it dries.

Corner Bead Damage

• Hammering a window surround also might damage the metal corner bead underneath the plaster or drywall. If the corner bead bends or warps, chances are you will have to rip out the damaged section and replace it with a new piece.

Considerations

• If possible, install wood trim without hammering the walls surrounding the window. If the trim doesn’t fit well, there are options for camouflaging the problems. For example, use wood filler or caulk to fill visible gaps between the trim and the wall.

Sanding

• If the wall or window edges are too crooked or bowed for you to install the wood trim, sand down the plaster or joint compound rather than hammer it flat. Use 80-grit sandpaper, which will level surfaces quickly. Sandpaper grits lower than 100 create scratches and gouges that will be visible through paint, so limit your sanding to the area directly under the wood trim to avoid having to apply several coats of joint compound to hide the sandpaper marks later.