Causes of Plaster Problems
Cracks, holes, bulges and detachment from the laths are some of the common problems with plaster installations.
These problems can emerge during the progressing plaster job or later in the succeeding years. Though these problems can be easily repaired, addressing the causes of plaster failure can save the plaster from further damage and can be very helpful in preventing such problems to reoccur.
1. Structural Failure
- Overloading. Load-bearing walls are prone to stress cracks. The stress imposed on beams, joists and studs might be greater than expected. This can be caused by renovations in some areas of house (e.g. cutting-in a door or window) wherein installation of additional load-bearing support was not considered resulting in additional stress directed to the walls.
- Soil settling and vibrations. The soil surface where a house lays can also affect its structural integrity. Clay soils are constantly settling according to seasons. Clay soils contract in dry seasons and swells in rainy season. This instability in the soil surface can cause the constant movement of the house’s foundation.
Another cause of structural instability is vibration. A house located near railways, busy highways, fault lines and constant blasting is subject to destructive vibration.
These two factors (especially when combined with the deterioration of laths and poor quality plaster) can cause plaster to detach from the lath.
2. Plaster Installation Failures
- Improper mixing proportions. Greater ratios of aggregate materials (like sand) compared to the cementing material (gypsum or lime) can cause the weakening of the plaster that can result into disintegration.
- Incompatible coats. Cracks would appear on finishing coats that was overlaid on perlite-mixed base coats. The finish coating must be redone which would be time consuming. To prevent this problem, fine silica or finely crushed perlite should be added to the finishing coat. This is necessary so that the two coats would achieve precise shrinking rates.
- Improper plaster application. “Chip cracking” occurs on finish coats that are applied on excessively dry base coat. Insufficient troweling and gauging plaster can also cause chip cracks to appear.
Over sanded and thin base coats on the other hand can cause fine and irregular cracks similar to map lines to appear at various points of the finished surface.
- Excessive use of retardants. Retardants slow down the setting rate of the plaster, enhancing its workability but if it is excessively used, the plaster won’t set within its normal time span which can lead to the softening and powdery texture of the plaster.
- Inadequate thickness. The plaster can fail if the required thickness is not achieved. The thin plaster may not be able to bear the load bearing stress that is normally attributed to the wall.
- Poor ventilation. The temperature should be between 55 to 700F to ensure proper curing of the plaster. A properly cured plaster would mean a durable plaster.
Too much heat would evaporate all the water from the plaster, hindering setting and making the gypsum return to its raw form (calcite gypsum). When the plaster freezes before it had set, it would be useless. If air is not properly circulated around the room, the plaster can rot.
Some causes of invasive moisture in plaster installations are leaking gutters, downspouts, plumbing pipes and roof. In traditional brick buildings, moisture is a common problem for there is no way that moisture can escape from the brick wall
Tagged with: Causes of Plaster Problems • chip cracking • moisture • perlite-mixed base coats • plaster failure • plaster installation failures • soil settling and vibration • stress cracks • structural failure
Filed under: Plastering contractors companies
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