How to Repair Styrofoam Beams

Mark Morris

Styrofoam can be finished to replicate nearly any surface from wood grain to brick to stone. The lightweight, easily sculpted material makes a flexible medium for many architectural details from crown molding to "marble" pillars. Faux beams made of styrofoam can be found in many interiors. As with many building materials, styrofoam has its downside too. The same lightweight, loosely bound structure that makes it ideal for so many uses leaves it vulnerable to damage from impact. It can be easily repaired with readily available materials.

Foam Beam Repair Techniques

  1. Clean the surface where repair is needed with a damp rag and detergent to aid in adhesion. Repair small blemishes with a touch up of paint, stain or even magic marker to cover the damage.

  2. Cover slightly larger dents and dings with latex painter's caulk. Use tube type caulk to avoid the potential mess of caulking guns. Apply enough to fill the damaged area and smooth with a dampened finger. Allow it to dry and touch up the paint or stain. Magic markers or wood stain pens are sometimes useful. You can get painter's caulk and stain pens in the paint department of any hardware store.

  3. Repair larger damaged areas with expanding foam insulation. It can be purchased with caulking at your local hardware store in an aerosol can. Try the foam on a scrap of plywood or cardboard to get a feel of how much it expands. Apply enough foam to let it rise to fill the void in the damaged area. Add more as needed until it swells a little past the line you want to shape it to.

  4. Use a sure form rasp, utility knife, or dremel tool to carve the foam down to the shape of the beam before the damage. Fill any small voids in the foam with painter's caulk. Apply enough caulk to the damaged area to fill it completely. Use a damp finger to smooth the repair. Allow enough time for proper drying before applying paint or stain to match.

  5. Seal the repair with a coat of sculptural arts plastic varnish. Apply a coat of paint or stain to match the rest of the beam. Paint the entire beam with two or three coats of sculptural arts plastic varnish to brighten the finish and add a layer of protection.