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How to Seal Wood Doors

Emily Beach

Like all wood products, wooden doors are susceptible to damage from moisture, humidity and temperature changes. When left unsealed, a door will absorb excess moisture from the air, which can lead to swelling or warping. These types of changes cannot only ruin the door's appearance, but they can also keep it from functioning properly. To protect your door against this and other problems, coat the door with a protective sealer. These sealers must be used in addition to stain, as stain is not designed to offer protection to wood doors.

  1. Set the door on a pair of padded sawhorses so you can easily access all areas. Some homeowners may be tempted to seal the door after it is installed. This makes it nearly impossible to seal some of the door's edges. It can also lead to drips and spills on flooring and furnishings.

  2. Sand the door. Even a new wood door needs to be sanded to remove handling marks and to open the pores of the wood to accept the sealer. Use a rough textured paper to remove any signs of damage. Sand again with a very fine grit to smooth out the wood. Clean away all sanding dust with a damp rag and a tack cloth before proceeding.

  3. Coat the door with a wood treatment solution or sanding sealer. These treatments are particularly important on softer woods, or on any wood species that tends to take stains and sealers unevenly. If you use a soft bristle paint brush for application, it will prevent blotches and discoloration as you seal the door. Wait for this treatment to dry completely before proceeding.

  4. Apply stain to the door to create the desired finish. Use an exterior grade product that offers ultraviolet (UV) protection. Avoid combination stains and sealers, as they rarely protect the door as well as a separate sealing product. Brush the stain on using a foam brush to go against the grain, then use a clean rag to wipe the stain down the direction of the grain. Wipe away excess stain and allow the door to dry before sealing.

  5. Seal the door with a polyurethane sealer. Apply this material using a clean paint brush, working in the same direction as the grain. Wait for the sealer to dry, then examine the door's texture. A properly sealed door will feel slightly rough to the touch. This indicates that the sealer has effectively closed the wood's pores, leaving a bit of excess sealer on the surface. Sand the door with a very fine sandpaper to remove this texture, then hang the door in the frame to complete the project.