Whenever a new roof must be considered, careful deliberation must be given about all available options. Replacing a roof is a very costly venture and for this reason, the choice is often made to have an overlay done in order to save time, labor and disposal costs. Of course, whether or not this is possible depends on the shape of the roof deck and how many layers already exist.
Tear-Off Indications
While it is often thought that an overlay is like putting a new dress over an old one or putting on make-up over an unwashed face, such comparisons should not be the only reason for removing a roof. Following are some things to consider which, if applicable, may indicated a need to replace the entire structure.
- Ice Damming – In areas where the temperature goes below 30 degrees, an old system that does not have water or ice protection membranes and is prone to ice dams may may require removal. Even structures that are twenty years old without such protection but no prior problems could likely experience damage when cold weather hits.
- Building Code – Many times it is not up to a contractor but is actually a building code requirement to remove an existing roof if there is more than one layer present. It is important to contact a local building inspection department to be sure whether or not a new roof can be installed over an old one.
- Severe Damage – If the existing roof is not in overall bad shape but has specific areas of aging or damage such as crooked rows or severly curled tabs, little doubt remains that the entire roof must be removed and replaced.
- Decking Deterioration – During an inspection, if sagging between trusses or rafters is noticed, that is a sign that a deck may be damaged or is deteriorating. This could be caused by a fungus and if not properly treated, may have spread across the entire deck. If such is suspected, then serious consideration should be given to replacing the entire roof.
- Inappropriate Shingles – If lightweight shingles are being covered with heavyweight shingles, a structural expert should be consulted to determine if the existing structure can handle the additional weight of new shingles. If considering replacing current shingles with lighter weight ones, the outcome is generally not good as bumps and ridges are often visable.
- Shorter Life Span – Although this is simply a theory, many roofing experts agree that putting a new layer of material over an older layer can shorten the lifespan of the roof by approximately ten to twenty percent.
If any of the conditions mentioned above are evident on a roof, a complete tear off is probably the best solution. For anyone who is unsure about which option is the right one to select, the wisest decision to do is consult with a reputable roofing company to get professional advice on such an important project – and leave any re-roofing unsure thoughts in the hands of expert roofers!