The two most used interior wall materials are
gypsum wallboard (or drywall), and plaster. Plaster was used over
brick, stone or frame construction, and whitewashed, painted or
wallpapered. If you own an older home, built pre-1950s, it probably has
plaster walls and ceilings. Plaster is made of a mixture of Portland
cement, sand and water applied in layers to a wood or plasterboard base.
Over a period of time, settling or shrinking of walls produces fine stress-cracks.
Professional plasterers have the materials,
plaster tools, and skills needed to repair these cracks, but do it
yourselfers can also tackle the smaller jobs.
Small, thin cracks can be filled in with patching
plaster or high grade, lightweight non-shrinking spackling compounds.
The steps to follow go like this:
First, remove all the loose plaster with a thin
screwdriver or knife, cleaning the crack so it is wider at the bottom
than on the surface. This enables better adhesion for the new plaster.
With a damp cloth or brush, remove loose plaster dust. If you are using water-based patching plaster, dampen the crack.
Using a criss-cross motion to work it in, fill the crack in with patching plaster or spackling compound.
Next, feather the edges of the patched area so it
will be less visible. Go about 2" on each side of the crack, using a 6
inch wide flexible putty knife. Smaller putty knives have a nasty habit
of leaving gouges.
When the patch is dry, lightly sand and then paint
over it. On more humid days, you can use the low temperature setting on
a hairdryer to speed up the plaster drying, but watch out. If you apply
too much heat you'll end up with more cracks. (cn-stonenet.com)
