How to Restore Polyurethane Coated Doors

Polyurethane is commonly used to protect wood surfaces because it is durable and nearly impermeable. Despite its durability and longevity, polyurethane will eventually break down and start to show wear after many years -- after all, it won't make wood invincible. This is particularly true of doors, especially exterior doors, which might see heavy use or are exposed to the elements. Wooden doors and other wood surfaces that have been coated with polyurethane should be refinished every 10 to 15 years to keep them looking their best.

Screwdrivers
Sawhorses
Handheld belt sander
80-to-100-grit sanding pad
200-to-220-grit sanding pad
Sanding block
Sanding sponge
Tack cloth
Wood stain
Roller, sprayer, rag or paintbrush
Clean, lint-free cloth
Polyurethane
Lamb's wool or foam applicator
400-grit sandpaper

Instructions

- 1
  Remove the doors from the frame. Remove all the hardware from the door, including knocker, strike plate, doorknob and hinges. Place the door on a clean workspace or on a pair of sawhorses in a well-ventilated room.
- 2
  Sand the old finish from the door with a handheld belt sander fitted with an 80-to-100-grit sanding pad. Strip the finish from both sides and all the edges. If there are any intricate engravings or other hard-to-reach spots, sand with a sanding block or sanding sponge.
- 3
  Wipe the dust from the door with a tack cloth. Sand the door again with 200-to-220-grit sandpaper. This will give it a smooth surface. Remove the dust with a tack cloth.
- 4
  Stain the door with a wood stain of your choice. Stain can be applied with a roller, sprayer, rag or paintbrush. Once the door has been stained, wipe the wood with a clean, lint-free cloth until the wood feels almost dry and no more stain comes off on the cloth.
- 5
  Apply extra coats of stain if you want deeper color saturation. Allow each coat to dry before applying another one. Repeat the process for the other side of the door.
- 6
  Pour a small amount of polyurethane directly onto the wood. Spread this into a thin, even layer across the entire door with a lamb's wool or foam applicator. Allow the polyurethane to dry.
- 7
  Scuff the polyurethane by lightly sanding the entire door with a piece of 400-grit sandpaper. Do this by hand, not with the belt sander. Wipe away the dust and apply as many as four more coats of polyurethane. Do not scuff the second-to-last coat.
- 8
  Reattach the hardware you removed earlier. Reinstall the door in the door frame.

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