Carol Tabb of Columbia plans to replace the roof, front door and screen door on her 25-year-old townhouse this year. She understands that doors, roofs, wood, etc. expand and contract with extreme cold and extreme heat, and asks whether any particular months favor these types of replacements.
Expansion and contraction of materials because of temperature extremes is not likely to be a significant factor for the work you are planning, although it would be better to avoid installing the new roof in freezing weather.
Very low temperatures can increase the risk of problems with an asphalt shingle roof installation, mainly because of stiffness of the cold shingles and lack of adhesion between courses of shingles.
Cold shingles are much more brittle because of the properties of the asphalt binder in them and can crack or break while being handled. Also, if a bundle of shingles has been stored on an uneven surface, the shingles from that bundle will tend to retain that uneven shape while cold. As a result, they might not lie flat while being nailed, and nails could break through the shingles rather than neatly puncturing them.
If the new roof is installed without removing the old shingles its surface might look uneven.
Low temperatures also affect the adhesive on the underside of shingles. The adhesive is intended to bond the shingles togetherm after they are installed, to keep them from being lifted and torn by high winds. Sufficient heat is needed, mainly from sunlight, to soften the adhesive and allow the shingles to bond in the days and weeks after installation.
High winds before shingles have bonded often tear shingle tabs off the roof. If shingles are installed in very cold weather, it is advisable for the installer to apply plastic roofing cement under each shingle to create an immediate bond.
Dean Uhler has been a home inspector for more than 12 years and is president of Baltimore-based Boswell Building Surveys Inc. Uhler is a member of the American Society of Home Inspectors (ASHI) and is the treasurer of the Greater Baltimore Chapter of ASHI.
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