How to Repair a Gap in Exterior Wood Trim


Most gaps in exterior wood trim are caused by poor installation of the trim or shrinkage in the wood trim. Gaps in exterior wood trim must be repaired with a material that flexes with the natural expansion and shrinkage of wood. Repair material should not create another gap or crack. Before deciding to fill a gap in exterior trim, determine if it is possible to remove and match a piece of the trim--cutting a new piece to eliminate the gap. In most cases, removal and trim replacement is not cost efficient. Repairing by filling the gap with a silicone-based caulk is usually the preferred course of action.

Things You'll Need

  • Putty knife
  • Screwdriver
  • Utility knife
  • Exterior silicone-based caulk
  • Caulking gun
  • Sponge
  • Towels and rags
  • Primer
  • Paint
  • Scrape dirt, paint and old caulking out of the gap in the exterior wood trim, using a putty knife, screwdriver or utility knife.

  • Snap the caulk tube into the caulk gun. Squeeze the trigger to fill the gap with caulk.

  • Smooth with a wet sponge, small putty knife or your finger while the caulk is still pliable. Tidy with a towel.

  • Follow manufacturer's instructions for caulk cure time and temperature installation parameters.

  • Finish with primer and paint to match.

Tips & Warnings

  • This process can also be followed for gaps created by a loose trim piece, window trim gaps, fascia board and soffit gaps or siding issues.
  • Do not use wood filler to repair a gap in exterior wood trim as it shrinks, falls out and cracks in extreme weather conditions.

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  • Photo Credit glazier image by Greg Pickens from
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