HABITAT ANSWERS: A roofing system is more than just its membranes. Roof maintenance must address not only the protective layers covering the underlying roof deck, but also the roof-level components, such as parapets, copings, base flashing, counterflashing, bulkheads, chimneys, railings, drains, and scuppers, all of which are exposed to the elements and therefore vulnerable to water infiltration.
So you may be right. Repairing a worn roofing membrane will not stop leaks if water is entering through cracks in a parapet wall or seeping underneath the roofing layers because of defective or missing counterflashing.
A common but ultimately detrimental method of roof "maintenance" is to apply tar everywhere at the roof-level, including on parapets, coping stones, bulkheads, and other masonry.
Tar (asphalt) acts as an effective sealant on roofing membranes but not on masonry, which needs to breathe. It prevents stonework and brickwork from releasing the incidental moisture that they naturally absorb. Also, tar eventually melts and cracks, creating pockets that act as a conduit for more water to enter. Trapped water freezes and expands, creating more cracks, loosening bricks and stones, and weakening the structural integrity of the masonry, making a bad situation worse.
Another overused and ultimately futile maintenance practice is repeatedly "capping" a roof by applying a new membrane on top of the existing layers. Cap sheets can add a supplemental level of waterproofing if the underlying roof structure is generally sound. But in too many cases, cap sheets are applied on top of badly deteriorated membranes, trapping saturated water.
In addition, the new membrane will not adhere properly if the underlying layers are peeling, bubbling, fraying, or otherwise defective. Repeated layers of cap sheets can also distort the pitch of the roof, disrupting drainage and causing ponding.
While capping a roof is much less expensive than tearing up the existing roof down to its deck and completely replacing the membranes, capping provides only temporary relief because it doesn't fix the underlying defects.
Furthermore, manufacturers may give a limited pro-rated warranty for a cap sheet, but you will be unlikely to receive the type of long-term No Dollar Limit (NDL) warranty typically provided on a full roof replacement.
Even if you've repaired defective roof-level masonry and replaced the roof itself, you can't forget about the roof for 20 years until the NDL is up. A regular roof maintenance program is still required and should include checking for the following items:
Although cash-strapped boards may be tempted to defer necessary repair and maintenance items (or mistakenly overlook them), addressing potential problems early on will avoid more extensive — and expensive — work down the line.
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