How to Fix a Horizontal Hairline Crack in a Plaster Wall

Plaster is a composite of plaster dust and water. When it dries, it becomes hard but not dense. Because of this, tiny cracks can form from the house settling or from accidental causes, such as moving furniture. When a horizontal crack forms in a plaster wall, there is a chance it will spread, running the width of the wall, making it less sturdy. To avoid any further damage, you can patch the horizontal crack with just a few items.

Joint compound
Plastic putty knife
Fiberglass tape
Hand roller
Fine-grit sandpaper
Tack cloth
Interior paint
Paintbrush

Instructions

- 1
  Spread joint compound along and into the horizontal plaster crack using a plastic putty knife. Press the joint compound into the crack firmly, allowing it to "overflow" back onto the surface of the wall.
- 2
  Scrape away any excess joint compound with the plastic putty knife, then adhere fiberglass tape along the horizontal crack on the plaster wall. Press it down firmly with the palm of your hand, then go over it with a hand roller.
- 3
  Spread another layer of joint compound over the fiberglass tape using the plastic putty knife to conceal the tape. Scrape away excess compound as you did before. Let the compound dry according to the manufacturer's suggested drying time.
- 4
  Sand the joint compound across the horizontal crack in the plaster wall with fine-grit sandpaper until it is flush with the wall. Then wipe down the wall, including the patched crack with a tack cloth.
- 5
  Paint over the horizontal patch with a matching paint, if necessary, using an interior paint and paintbrush to finish.

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