The design of tongue and groove walls vary greatly, but all designs feature flat surfaces, called tongues, and slotted surfaces called grooves. The challenge when preparing to paint a tongue and groove wall is removing the paint and smoothing the surface without damaging the wood. Traditional sandpaper works well for the tongues, but not for the grooves. Paint stripper is extremely effective at removing the old paint from the grooves, and steel wood will smooth away any imperfections.
Smooth the flat surfaces of the wall with a pad sander and 150-grit sandpaper.
Apply a liberal coat of chemical paint stripper to the slotted surfaces with a paintbrush. Wear heavy rubber gloves and eye protection when applying the stripper.
Allow the paint stripper to rest on the wall until the paint blisters.
Scrape away the blistered paint and smooth the surface with a steel wool pad while wearing the gloves and eye protection. Do not use a paint scraper here, as you will likely damage the surface of the wall.
Wipe down the grooves with denatured alcohol and a clean steel wool pad to remove the stripper and clean the grooves.
Wipe down the entire wall with a sponge dampened with water and allow the wall to dry before painting it.