Short Answer
The appropriate tear-off strategy depends on existing layers, code, manufacturer requirements, substrate condition, roof type, and project scope.
Detailed Explanation
The decision to remove all existing roofing layers (full tear-off) or install over existing roofing (re-roof) depends on several factors. Building codes typically limit the number of roofing layers to two. Manufacturer installation instructions may require a tear-off for warranty compliance. If the existing roof has multiple layers, all must be removed. If the roof deck is damaged or deteriorated, tear-off is necessary to inspect and repair the deck. If the existing roofing is in poor condition, installing over it can telegraph imperfections to the new roof. A full tear-off is generally preferred because it provides full visibility of the deck, allows proper inspection, and ensures the new roof is installed on a clean, sound surface. In most cases, a full tear-off is the recommended approach.
Why It Matters
Installing over existing roofing without proper evaluation can hide deck damage, add excessive weight, and compromise the new roof's performance and warranty.