For large infill areas, the preferred patching material is a lime-putty mixture – one part lime putty to three parts sand.Each one of the links in the layers has the potential to fail. The bonding agent need not fail (adhesive failure) for the system (the collection of layers) to fail (cohesive failure). Bonding agents are a “paint like” material with a limited track record (compared to plaster and plastering techniques – a few decades versus tens of thousands of years).A patching material should be chosen – whether it be bonding agents, a lime-putty mixture or a combination of lime putty and gypsum – based on how long the repair needs to last. Possible causes of plaster failure range from water damage to structural problems. Patching materials: Before applying new plaster, it is important to fix the problem that caused the plaster to fail.
#Plaster washers Patch
These instructions should be followed to patch holes: After the adhesive sets, the injection holes and cracks are simply filled. The flexibility of the adhesive allows the plaster to move as naturally as it did when it was first applied. The adhesive provides a dispersed area of attachment that is flexible, leaving nothing on the surface to cover. The preferred method of stabilization is the injection of a specially designed water-based adhesive. Because the cracks will reopen under the mesh tape and the washers will show at some point, this type of repair is only short term. The mesh tape, screws and washers also need to be covered with multiple layers of joint compound and then sanded and/or sponged.
The cracks do not go away or come together they are hidden under tape and joint compound. The inevitable cracks that result from this method need to be bridged with a mesh to prevent them from showing. Second, screws and washers create a very hard, narrow point of attachment that doesn’t move with the plaster or the building when the plaster moves the washer around, it will break. First, washers and screws often crush plaster to the lath, fracturing its structure.
The conventional approach – using washers and screws to compress plaster to laths – has a couple of issues that make it incompatible with repair.
Articulations where these systems meet allow movement between them. The one common factor in each of these building components is that they are all similarly flexible: masonry foundations expand and contract with moisture and temperature changes, while wooden-braced frames with attendant framing and laths expand and contract in concert with the foundation. A typical residence from the 18th or 19th century was built with a stone or brick foundation and a braced frame with studding to attach strips of wood lath, which were then covered with lime, cattle hair (not horse hair) and sand plaster. In choosing a method to stabilize plaster, it is important to have an understanding of the techniques and materials used in the construction of historic buildings. Conversely, once plaster is stable, almost anything done to its surface will work. Repairing plaster begins with stabilization – if plaster is not stabilized, repairs will simply not last. In this case, the plaster wall was stabilized incorrectly – instead of using screws and washers, which often crush plaster to the lath and don’t allow movement with the house, the better method is to inject a flexible water-based adhesive. Plaster repair begins with stabilization, but it must be done correctly to stand the test of time.
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