One of the most durable exteriors down through the ages has been a lime, sand and water paste called stucco. This coating pretty well retained this mixture until the invention of Portland cement in the late 1800's which saw the cooking of the lie in kilns to make the resulting cement harder. In fact, stucco siding could well be the very first exterior known to man. Stucco mixes are available at the building supply store but most stucco contractors make it from scratch using three parts sand, to one part Portland cement and a small amount of hydrated lime.
Like its indoor cousin, plaster, stucco needs to have a rough finish or lath to grab onto otherwise it might fall off in time. Plasterers used to use wooden laths which were installed perpendicularly to the vertical wall studs. Outside, stucco contractors use a lath made of a zinc-coated, woven-wire mesh which allow the stucco paste to key or become embedded into the spaces. In most cases stucco can go right over concrete without a lath but when the exterior is wood the wire mesh is used and kept away from the house by about 1/4 . The house is sheathed with plywood or oriented strand board, then tar paper or house wrap is applied followed by the lath. In some cases wooden lathes are attached to the exterior after the tar paper, or damp-proof membrane, has been installed. This gives any moisture getting in behind a larger channel to run down behind the stucco.
Stucco is usually applied in three layers but some contractors will scrimp and only use two layers. In the three-layered system the first one, which is keyed into the lath, is called the scratch coat. This is usually 3/8 , or 10mm, thick and is scratched with a broom to form keys in order to hold the second coat. The second coat is called the brown coat and is also 3/8 thick. This layer sets the surface up for the final or finished coat which give the stucco its appearance. Stucco is easy to color by mixing a dye in the final coat but a curing period of six weeks should be allowed for the stucco before a paint job. Stucco on homes can last well over a hundred years in the right conditions and small dents and cracks on stucco are easy to repair.
Many homeowners are tired of their brick facing and will apply stucco to change the look. In this case they do not need any lath but here are a few pointers before starting.
Stuccoing is not a job for the faint of heart. It takes a lot of patience and a keen eye. For more information on how you can get a professional to do the job contact our Contractors Directory or post your project on line at TrustedPros.ca and one will contact you.
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