How to Repair a Hairline Crack in a Soffit Board

by Kim Blakesley

A hairline crack in a soffit board is not only an eyesore but an open door to water damage from inclement weather. The moisture seeps into the wood and causes the soffit board to deteriorate. It is possible to fix a hairline crack without removing the board. Fill the crack with a cyanoacrylate glue, epoxy putty or paintable wood caulk. Each process is less time consuming than replacing the entire board and more cost effective.

1. Cyanoacrylate Glue

1 Clean the hairline crack with a rag. Sand to remove any paint chips or splinters. Sand the area around the crack if necessary.

2. Cyanoacrylate Glue

2 Put on rubber gloves. Cyanocrylate glue will stick to your skin and any other area it may touch. Wear old clothing to avoid spoiling your good clothes.

3. Cyanoacrylate Glue

3 Position the end of the open bottle of cyanocrylate glue directly over the hairline crack. Squeeze the glue into the crack while moving the bottle along the length of the crack.

4. Cyanoacrylate Glue

4 Position the end of the bottle of cyanocrylate activator over the hairline crack. Squeeze a line of activator over the glue while moving the bottle along the crack. The chemical reaction between the activator and the glue will cause it to set in about 10 seconds. It will be completely cured within 30 seconds.

5. Cyanoacrylate Glue

5 Allow the glue to cure 30 seconds. Sand the area with 180-grit sandpaper until smooth. The area is now ready for paint.

6. Epoxy Putty

1 Clean the hairline crack by dragging a putty knife through all areas large enough to enter. Sand the surface with 180-grit sandpaper until the surface is smooth with the remaining board. Sanding will remove any small chips of paint from the surface.

7. Epoxy Putty

2 Wearing rubber gloves, squeeze the epoxy putty to activate. Continue to work the putty until it is malleable. Create a long slender snake-like roll.

8. Epoxy Putty

3 Place the snake-like roll over the hairline crack. Press the roll into the crack with your fingers.

9. Epoxy Putty

4 Scrape over the surface with a putty knife immediately after pressing the roll of epoxy putty into the crack to remove excess.

10. Epoxy Putty

5 Allow the epoxy putty to cure five minutes. Sand the surface with 180-grit sandpaper until smooth.

11. Paintable Exterior Caulking

1 Clean the area of the crack with a rag. Sand the surface until smooth. This removes any small paint chips and splinters.

12. Paintable Exterior Caulking

2 Cut the end of the tube at an approximate 45-degree angle and insert into a caulking gun.

13. Paintable Exterior Caulking

3 Place the end of the tube parallel with the soffit surface. Position the tube over the hairline crack. Squeeze the trigger and move the caulking tube along the surface of the soffit board until the entire hairline crack is covered.

14. Paintable Exterior Caulking

4 Wet your finger. Pull your finger over the crack to press the caulk as far into the crack as possible. Remove any excess with your finger.

15. Paintable Exterior Caulking

5 Allow the caulk to dry 30 to 60 minutes.

Items you will need

  • Ladder
  • Rag
  • 180-grit sandpaper
  • Rubber gloves
  • Work clothes
  • Cyanocrylate wood glue and activator
  • Putty knife
  • Epoxy putty
  • Paintable wood caulk
  • Caulking gun
  • Utility knife
  • Water

About the Author

Kim Blakesley is a home remodeling business owner, former art/business teacher and school principal. She began her writing and photography career in 2008. Blakesley's education, fine arts, remodeling, green living, and arts and crafts articles have appeared on numerous websites, including DeWalt Tools, as well as in "Farm Journal" and "Pro Farmer."