Roofing Shingle Replacement The Total Envelope Approach

 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.  

Take It Off

 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.  


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