How to Apply Exterior Lime Plaster

Wash away dirt, grit and other debris from the wall. If there is considerable grimy buildup, scrub the wall with a solution of one-quarter cup trisodium phosphate mixed with 1 gallon of hot water.

Put on a pair of heavy-duty rubber gloves and mix 3 parts coarse sand with 1 part lime putty. Mix these components together by hand or use a garden hoe, trowel or drill with a mixing attachment; but use gloves regardless.

Scoop up large handfuls of your freshly prepared plaster and spread it over the wall. Alternatively, you may scoop the plaster with a trowel.

Press the plaster into any cracks or grooves in the existing wall before smoothing the plaster. Start at the top of one end of the wall and work your way down, then across. Work on sections that you can comfortably reach with a ladder.

Smooth the plaster with a trowel. You may find it helpful to work with a partner -- one person scoops and presses the plaster into the wall while the other follows and smooths the plaster. Make the plaster as smooth as you can, or move the trowel in a wavy pattern for texture according to your taste. Any dramatic texture you create on the initial layer will show through on the second layer.

Wipe excess plaster from the trowel on the lip of your mixing container. Allow the plaster to dry. Check it after four to eight hours by pressing your thumb against it. If you leave a dent, the plaster needs to dry longer.

Drag a lathe scratcher over the wall in a diamond pattern. This will create shallow grooves to which the second layer of plaster can adhere -- any dramatic texture you added during the first application will still show through, while the scratches will be filled in by the second application of plaster. Moisten the wall slightly with a spray bottle or a garden hose with a misting nozzle.

Spread the second layer of plaster over the wall with your trowel. Use circular or crescent-shaped motions to give the plaster some texture as you spread it evenly over the wall. Alternatively, you can keep the wall smooth or work your trowel using a different pattern for a distinct texture.