The practice of laying over an existing roof, also known as re-roofing or overlaying, involves placing new shingles or roofing material directly on top of an existing layer. In most cases, building codes limit this to two layers. Adding a third layer is generally discouraged because it adds excessive weight to the roof structure, which can compromise safety and lead to structural damage.

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Before deciding to overlay, it’s important to evaluate the condition of the existing shingles and the roof deck. If the current layer is significantly damaged or deteriorated, a complete tear-off is often a better option. Overlaying over damaged shingles can trap moisture, cause leaks, and reduce the lifespan of the new layer.

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Moreover, building regulations and manufacturer warranties may have specific guidelines on overlaying. In some cases, warranties for new shingles may be void if installed over old ones. Roofing experts in Edinburgh can provide valuable insights on whether an overlay is suitable, ensuring compliance with local building codes and optimizing roof longevity.