It's a certain rule of thumb: With old houses comes cracked plaster. The Bolens have already patched some of the plaster in the downstairs foyer and dining room. They might have opted for the cheaper alternative -- covering the damaged plaster with drywall -- but the Bolens wanted to retain the historical integrity of the house by using materials that are period-authentic to the time when the house was built. In addition, for a cost just slightly more than that of installing drywall, the plaster will be more durable.

Following are the basic steps our restoration specialists followed in the plaster repair.

Begin by assessing the cracks and trying to determine possible causes. The plaster cracks in this old house appear to be settling cracks and are fairly common in a house of this age. In this case, there are large cracks that have been repaired previously, as well as mid-sized and tiny "spider cracks." There's also a drywall patch that was put there previously when an electrician had to gain access behind the wall when the house was re-wired.

Settlement over time is one cause of cracked plaster, but another is key disintegration. This is where the plaster protrudes through the wood lath to create a bond. It can also be caused by poor-quality plaster, water damage or normal wear and tear. The first step in repairing cracks is cleaning them out.

• Using a five-way tool or other scraping device, clean out loose plaster from inside cracks.

• In the case of larger cracks with plaster falling out, remove the damaged plaster to reveal the binding course.

• Knock old plaster through keys in the lath to establish a better binding course for the new plaster to adhere to.

• Restoration Terminology: A five-way tool is a single tool a variety of uses -- including scraping, cleaning, opening paint-cans, etc. The binding course is the area or surface that the plaster binds onto -- in this case, the wood lath. The key way is the term that refers to the spaces between the slats of the wooden lath.

• Large cracks, where the lath and plaster have been pulled away from the wall, can be re-secured using metal plaster washers and ordinary 1-1/2" or 2" drywall screws. This secures the existing plaster to the wood lath.

• Secure screws and washers diagonally on either side of loose plaster, about 1-1/2" to 2" from the crack.

Prepare and Apply a Base-Coat

This plaster repair consists of two coats: a base-coat plaster for re-establishing the key-ways for a binding layer, and a top-coat finish layer to provide a smooth surface. Our base-coat is a lime-based plaster, also called "brown coat," that is heavily sand- or silicate-based.

• Combine base-coat plaster using room-temperature water, following the manufacturers instructions. Hot water can cause the plaster to set up too quickly.

• Using an electric drill with paint-paddle, mix the plaster to about a sour-cream consistency and allow mixture to sit for a few minutes as it starts to thicken -- or slake.

• Mist the lath with water lightly , being careful to avoid over-saturating the wood. This will help to prevent the lath from wicking moisture out of the plaster, causing it to dry too quickly and possibly result in more cracking.

• Using a trowel, squeeze base-coat into the cracks , making sure to get it into the keys of the lath.

• Smooth over crack and angle off excess .

• Depending on humidity, the base coat can take from 2 to 24 hours to set up completely. Allow a couple of days for it to dry completely.

• Once the base coat has dried, sand to a smooth finish

Repairing the Previous Plaster Patch

A previous repair to the plaster was made with a drywall patch and gypsum. However, we used a lime-based plaster for repairing the cracks. Those two materials cannot be mixed since gypsum and lime create a negative reaction. To smooth out the rough patch, we skim-coat the area with more gypsum compound and smoothed down our finish-coat even with the patch, feathering it in for a smooth appearance. The compound was applied using a 12" knife and spread smooth . Once the job is done and the surface has been painted, it the two surfaces should be essentially identical.

Apply Finish-Coat

The final step is to apply the finish coat. The finish coat is much finer than the base coat, and has a high lime and talk content that gives the plaster a sheen.

• Spread the finish coat evenly over dried base coat.

• The finish coat can also be used alone to cover small, hair-line cracks.

• Polish the plaster repairs by lightly spraying with water and smoothing over with grout float.

• Once the finish coat has dried, the newly repaired plaster can be given a fresh coat of paint or wallpapered.