How to Seal a Crack in a Wood Mantel

A wood mantel adds an ornamental facing for a fireplace. Since wood is not as durable as metal, it can crack due to exposure to high temperature or moisture. When cracks occur, you can repair the holes easily by using wood filler or epoxy filler and then using a polyurethane sealer.

Tools and Materials

  • Wood or epoxy filler
  • Putty knife
  • Medium- and fine-grit sandpaper
  • Paintbrush
  • Wood stain
  • Polyurethane sealer
  • Staining sponge

Step 1 – Clean the Cracked Portion

Inspect the entire surface of the mantel to look for cracks. Check rotten areas as well. Remove any loose debris inside any crack and gouge out any rotten parts using a putty knife. If there are any splinters, pull them out using a knife. Sand the surface of the mantel, including the inner surfaces of the crack if possible.

If there are a lot of cracks to repair, it is best to make a full repair so as not to waste time and effort. After cleaning the cracks and getting rid of rotted parts and debris, sand the entire facing with a medium-grit sandpaper. Follow up with fine-grit sandpaper to remove rough edges. Clean the dust off with a piece of cloth or rag.

Step 2 – Fill the Cracks with Filler

Mix the wood filler or epoxy filler according to manufacturer’s instructions. Use a putty knife to press the filler into the cracks. Wipe off any excess filler with a damp cloth. Level the filler with the surface of the wood so it blends seamlessly. Leave the filler to cure for a couple of hours depending on the manufacturer’s instructions.

Step 3 – Sand the Entire Mantel

To protect the wood from further damage and to repair minor scratches and cracks as well, it is necessary to seal the mantel with polyurethane. Prep the wood by sanding it with a fine sandpaper to remove any uneven surfaces, especially on the dried fillers. Clear the dust off with a piece of cloth.

Step 4 – Stain the Wood

Apply a coat of stain onto the surfaces of the facing to enhance its appearance. Stain it evenly and thinly with a staining sponge or rag during the first coating. Always start from the top going towards the bottom. Leave it to dry. Add a second coat to darken the color if preferred. Allow the stain to dry.

Take note that these chemicals produce fumes that are harmful to the health. Always wear a respirator, eye goggles and gloves for body protection during application.

Step 5 – Seal the Wood with Polyurethane

Polyurethane sealer is the best type of sealer for wooden facings. Before the application of the sealer, be sure that the stain has dried completely. Apply the sealer using a paintbrush. Start at the top going down to the bottom. Ensure that the coat is thin and even. Apply several more coats. Wait for the sealer to cure for about 24 hours or so. To facilitate the drying process, provide sufficient ventilation in the room where the mantel is located.