As we approach the 2013 construction season, it’s time to begin planning for any major building envelope projects that are needed at your property. In fact, if you are only planning now, you are behind schedule already. Getting your job “out on the street” early in the season, when contractors are looking to line up work for the new year, can often result in significant savings as opposed to waiting until the weather has turned.
Perhaps the biggest single mistake that can be made when devising a scope of work for a roofing shingle replacement project is thinking of the roof of any structure as a series of individual parts to be replaced individually. While there are many separate and distinct products included in a typical roofing system, replacing any of the individual parts without replacing adjacent, related components is a major compromise.
It goes without saying that roofing shingle replacement must also include replacement of any existing underlayments, such as self-adhering waterproofing membrane (i.e., Ice & Water Shield) and felt, and the majority of roofing jobs do include this minimum scope. However, oftentimes we are asked to investigate recently-replaced roofs that continue to leak. In many (perhaps most) of these instances, leakage continues to occur due to water penetrating at areas where the scope of work was compromised in order to save money.
For instance, any proper roofing shingle replacement must include removal and replacement (or re-installation, if the material is fit for re-use) of the above-roof siding at cheek walls and/or dormers. Without removing some of the above-roof siding, proper transitional underlayments cannot be installed. As a minimum, self-adhering membrane should extend 18” up any above-roof walls and 18” across the roof surface, more if possible. Without removing the siding, there is no way to install these critical underlayments. And in the harsh New England climate, anything less than this minimal use of self-adhering membrane is a recipe for disaster. It’s safe to say that the majority of “new” roofs that continue to leak do so because of this particular shortcoming, more than any other individual flaw.
Regarding the use of self-adhering waterproofing membrane, it must be understood that the requirements of the current edition of the Massachusetts state building code are the absolute minimum, and simple compliance with these requirements is not adequate to resist leakage under severe ice dam conditions. The winter of 2010-2011 was among the worst in recent memory for ice damming, and most people can probably remember seeing ice dams at the edges of roofs, some of which were more than a foot thick, with snow and ice build-up extending 10 feet to 15 feet up the surface behind the dam. Formation of ice dams is an environmental condition, and can’t be stopped. Ice dam leakage, however, occurs when the snow and ice in contact with the roofing shingles melts below the snow cover, typically due to heat loss through the ceiling/attic floor into the attic space, forcing liquid water to back-up through the shingles. If all that was installed at the eaves was enough self-adhering membrane to comply with current code (in some cases as little as three feet at the eaves), the roof could easily leak as this melting occurs. In fact, during the winter of 2010-2011, countless homes did leak.