In many older homes, built over 50 years ago, the interior trim was never painted.  Instead, the trim was left natural, stained and or top coated with polyurethane. Over time, some of these homes had the trim painted over the stained wood.  If the trim was not properly prepared, the trim will start to crack and bubble.  This occurs because the top coat did not adhere to the base which is often a type of urethane enamel.  Look to a future blog on how to properly paint over trim which is cracking and bubbling.  This blog will discuss the method on how best to paint over trim which has been stained and or top coated with a urethane enamel most popularly polyurethane.

You will need to sand the trim first to break down and dull the shiny enamel. Use a medium grit sandpaper such as 150 grit.  A sanding block is good for flat surfaces and a sponge sander is good for rounded and curved trim areas.

Identify nail holes, cracks and dings that need to be filled.  A wood filler such as “Minwax” wood filler is good for small nail holes.  Bondo may be necessary for large gauges in the wood.  Bondo can be shaped and formed by a skilled professional to fill in nicks and dings in detailed trim areas.  It will dry hard and adhere well to the trim.  Use a high quality caulking to fill in the cracks were trim boards meet and to seal the cracks where the trim meets the walls and ceiling if there is crown molding.  Be sure to use a paintable caulking, otherwise the paint will spread off the caulking.  Tape the walls to keep the caulk from spreading onto the walls.  Remove the tape after caulking.

Once you have filled and patched all troubled areas on the trim, you will need to sand these areas with a medium grit sandpaper, 120-150 grit.  Wipe down the trim to remove dust with a tack cloth after sanding.

If you are not painting the walls and ceilings, you will want to tape off these areas before painting. Use a light adhesive tape to keep the wall paint from lifting off when removing the tape.  A stain blocking oil primer such as “Kilz” or”Binz” is best to apply over an enamel or stained trim.  This will ensure proper adhesion of the top coat and will block the stain from bleeding through the top coat.

Use a light grit sandpaper, 220 grit, over the dried primer before applying the top coat.  Uses a quality paint for the top coat.  Benjamin Moore Advance or Sherwin Williams Emerald are both excellent products for interior trim.  Generally, a satin or semi-gloss finish is a desirable finish for trim.  Sand with a fine grit paper, 220-300 grit, between top coats for a smooth finish.

Paint the trim with a brush or sprayer for the best results.  A sprayer will provide the smoothest finish.


For more information on interior trim painting, please call ALL PRO PAINTERS  781-449-7262 or email at  You can also look us up at and fill out the contact form for a free estimate.