Are lath and plaster walls load bearing3/31/2024 ![]() ![]() To ensure the physical structure is not compromised, an expert should be consulted this usually results in some portion of the wall having to be opened. Large cracks in corners, around stairways, and on load-bearing walls are usually due to issues with the structural integrity of the building. If lath movement is not to blame and there is no physical damage to the structure, then they are simply patched. In spite of their best efforts, large cracks can still form. Often, capable architects and designers can anticipate a certain level of settlement, and construct finishes and structural elements to help compensate for this natural shift/displacement of load. It is imperative that all plaster work is conducted by an experienced professional.Įspecially common in older structures, building settlement is to be expected. Unfortunately, improper plaster application, or inadequate curing, often results in all of the plaster having to be removed and reapplied. Small damage can often be fixed simply be re-securing the plaster mechanically or with acrylic consolidants. Seismic damage restoration is often unique to each case and dependent on the extent of damage. Separation due to wood expansion, lath movement, and metal nail deterioration can often be solved by re-securing the lath to the framing this may require some plaster to be removed. Plaster can separate from the lath for a variety of reasons, including expansion of the wood lath/wood framing, deterioration of metal nails used to secure the lath to the framing, nails backing out of their position, seismic activity, and improper plaster application/inadequate curing methods. This concept basically describes the coefficient of thermal expansion and how the size of an object changes with a change in temperature. This movement over time causes stress and failures at the plaster layers. Seasonal weather cycles always play a role in the expansion and contraction of building materials. This will not only help protect the plaster application, but also will increase the longevity of the framing, insulation, and other structural elements within the wall. To help remedy this, a moisture-poof barrier should be installed between the exterior surface and interior framing, however, that was not always the case for historic buildings. ![]() Similarly, expansion can cause the wood lath to separate from the wood studs within the wall. When wood is repeatedly exposed to high humidity environments, it often causes the areas around the studs to swell, pushing the plaster surface outward or deflect. In our testing, we found that an 8mm rawlplug with a 5mm x 50mm screw into lightweight block we failed at about 50kg tensile (pull-out) load.High humidity environments can be detrimental for wood-framed structures. If you are drilling into a light weight block, use an HSS drill rather than a masonry drill.The screw used with a wall plug also needs to be the right size so that it can be tightened up firmly within the plug. Masonary drills in particular often tend to drill oversize holes (the best masonry drill for an 8mm plug is often a 7mm drill ). It works very well indeed in a solid wall made from brick, concrete, stone or, to a lesser extent, lightweight concrete or ‘aircrete’ blocks.Rawlplugs come in various sizes. This brand name has become genericised in the UK, being equally applied to wall plugs from competing manufacturers’ (Wikipedia).The rawlplug has been the workhorse in the fixings world for years and remains a top selling product. ‘The original wall plug was invented by John Joseph Rawlings in 1911, and marketed under the name Rawlplug. ![]()
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