How to Plaster an Exterior

Clean the wall surface well by sweeping it with a broom and then washing it by hand with soap and water or spraying it with a hose or pressure washer, depending on the surface. A wood surface, for example, may not accept pressure washing well because of the chance of gouging the wood.

Remove any siding or other material that is on the exterior surface before applying plaster. It is important that the surface be flat before applying the plaster.

Cover the wall surface to be plastered with roofing felt. Nail the felt in place with short roofing nails. Do not allow the felt to sag or bubble up. If plastering over concrete, apply a concrete bonding agent instead of felt. Allow the bonding agent to cure for at least 24 hours before applying plaster.

Secure metal netting over the roofing felt with staples or nails. This will help the plaster adhere to the felt and give it strength.

Open your container of premixed stucco and place a large amount on your plaster trowel.

Apply the stucco to your wall, covering the wall completely with a layer about a quarter inch thick. You can use whatever technique you like. Long strokes either horizontally or vertically with the trowel will result in a smoother, flatter surface than short strokes. Circular or wavy motions result in more texture. Allow this to dry for several hours.

Rake the stucco with a plaster rake to reduce the thickness by about half and then let it harden for 48 hours. Mist the wall every four hours with water in a spray bottle to allow it to dry slowly and keep it from cracking. It is important that this be a light misting by hand.

Apply a finish coat of plaster with your trowel. It is up to you how you finish the wall. It can be in a stucco-style with a pattern or you can smooth it completely and make it flat.

Allow the wall to cure again for another 48 hours, misting every four hours. The wall is then done or ready for more finishing, if you want to add more plaster or color.