Causes of cracks in the plaster along the exterior walls of the house

There are numerous reasons why the plaster along the exterior walls of your home will crack and the interior walls will look very unsightly. It is important to determine the cause of any cracks you find so that you can effectively repair them. Some of the most important causes of these cracks are listed below.

1. Structural cracks

Structural cracks, as the name implies, are caused by structural weaknesses in a building that are further worn away by certain conditions, such as a bathroom shower. A steam shower or steam room enclosure should be properly fortified with tiles.

The most important structural cracks include:

o Settlement resulting from inadequate or improperly located footings, the use of undersized or improperly spaced members, omitted bracing, or timber shrinkage

o These cracks are usually large and well defined, extending across the surface and through the plaster

o They can start near the corner of a door or window, or go up and down around the corner where two walls meet, or along the joints between the walls and the ceiling

2. Map and shrinkage cracks

Poor workmanship and the use of poor quality plastering materials are the main causes of what are known as “map cracks” and “shrinkage cracks”, that is, shrinkage in the plaster itself. There are ways to distinguish between these two types of cracks in the plaster. :

o Cracks in the map are usually caused by an incorrect bond between the plaster and the base

o Less noticeable than structural cracks and go through the plaster, but do not extend over the entire surface like structural cracks

o Are formed by a series of cracks that extend at various angles and span areas typically 6 inches or more in width

o Shrinkage Rifts, on the other hand, resemble Map Rifts, except that the Rifts themselves and the areas they enclose are much smaller.

o They differ from map cracks in that they do not go all the way through the plaster and are usually limited to the finish coat.

o Careless workmanship is often the cause of these cracks.

o Steam from a sauna can dilate these cracks; an infrared sauna unit is the best way to go

3. Loose plaster

Sometimes the keys or rivets that hold the plaster to the base break or become loose, causing the plaster to bulge and crack. On ceilings, around plumbing, bathroom and kitchen fixtures, it will often hang in this condition for a long time before falling off, held together by hair or the fiber of the plaster. Occasionally, the nails or fasteners used to hold the lath in place can corrode and break, allowing the part of the plaster that covers the loose lath or laths to sag and crack.

Tools needed for repairs

For small cracks and holes, a small diamond-shaped trowel or wide-bladed putty knife, for plastering larger areas, a plasterer’s trowel and a shallow pan.

materials needed

o Plaster of Paris or commercial repair plaster

o A small amount of regular glue if needed

or clean water

mix the plaster

o All mixing boxes and utensils must be clean and clean water from your glass sink, bathroom vanity or bathtub must be used in the mix.

o Special care should be taken that no traces of old set plaster remain in the mixing box.

o The water should be placed in the mixing box before sifting the dry plaster into the water.

o The mixture should then be shaken well to dissolve all lumps.

o It should be of a consistency such that the caulk can be picked up with a wide bladed knife and forced into the crack or break in the wall.

Using plaster of paris

If only a small amount of fresh plaster is needed, plaster of paris alone may be used. Plaster of Paris sets very quickly. If it is to be used without a retarder, only mix as much as can be put in in 10 minutes or less.