How to Tie in Plaster to a Wooden Beam

Base Coat

• 1

  Coat the beam with a mixture of oil bonding primer and nonskid grit texture additive for paint to create a surface the plaster can stick to, and minimize the swelling of the wood due to moisture absorption. Use a wide paintbrush to apply the primer mix and allow it to dry thoroughly.

• 2

  Cut expanded metal lath sheets to fit each face of the beam using tin snips and staple them in place with an air stapler, one staple every 10 inches. Use a hammer to bend in any corners or ends that stand out from the beam. This rough textured metal screen will "key" the plaster in place.

• 3

  Spread a thick coat of wall plaster over the lath with a wide drywall knife, or plastering trowel. Fill the gaps in the lath with plaster until it is even with the wire of the lath. Allow the first coat to harden.

• 4

  Apply the top coat with a wide drywall knife, keeping the tool wet to spread the plaster as smooth as possible. Work to present an even surface, covering the entire lath so that no wire shows. Allow the top coat to harden.

Finishing

• 5

  Sand the top coat smooth with a sanding sponge dampened with water to collect the dust. Rinse the sponge as the grit becomes clogged with plaster. Allow the sanded plaster to dry.

• 6

  Feel along the surface with your fingers, looking for rough or uneven patches. Apply a thin second top coat to any area that is not as smooth as you would like. Allow this final coat to harden. Sand the final coat with the sponge to finish.

• 7

  Apply a coat of straight oil bonding primer to the surface of the plaster to seal it. Use a paintbrush as before. Work in straight overlapping strokes to ensure proper coverage, painting the entire surface of the beam with the primer.