Homeowners often give little thought to the roof over their heads until there are signs of water damage such as mold, ceiling stains or, in the worst case, structural rot.  Too often people think that a newer roof is fine up until the end of its expected lifespan.  In fact, a common cause of water penetration is poor workmanship during installation.  Once the roofing materials contract in cold winter temperatures and expand in the summer heat, installation problems can begin to manifest as leaks.

There are two main types of roofs: sloped and flat.  The most common is a sloped roof covered in asphalt shingle or metal roofing.  Homeowners can expect to replace their asphalt shingles at approximately 20 years (or a little longer for light-coloured shingles, which absorb less heat from the sun).  Interestingly, a sloped shingle roof is not waterproof but instead relies on gravity to quickly move the water off the surface.  Metal roofs are waterproof and have a much longer lifespan at approximately 50 years. 

However, regardless of roofing material, the weakest spots in any roof are the gaps around dormers, vents, chimneys, skylights, etc.  If the flashing and seals around these protrusions are not installed properly, water can find its way beneath the surface.  

Flat roofs are common in multi-unit structures and modern, geometrical houses.  Flat roofs allow homeowners to enjoy upper decks for more outdoor living space.  There is only a slight slope on the roof to direct water to one or more drains.  This means that water has more time to penetrate so the materials and seals must be flawless to prevent leaks.  Flat roofs are usually traditional tar and gravel or newer, high-tech products with a smooth finish.  Again, the weak spots are the seams and flashing around vents, chimneys, etc. 

When buying a home, ensure that the inspection includes the roof.  A home inspector should check the shingles and gutter system for damage as well as inspect the flashing.  If problems are discovered, the inspector will likely recommend obtaining a written estimate from a qualified roofing company.  The cost of repairs can then be factored into the purchase price.

Regular maintenance can greatly extend the life of a roof and help prevent leaks.  Each autumn, after the leaves have fallen, clean out the gutters (rain catchers) and check for good drainage through the downspouts.  In addition to leaves, branches and dirt, occasionally people discover that critters have built nests in these areas!  Gutter covers are an option but they can be pricey.  Clogged gutters and downspouts cause water to back up onto the roof potentially causing leaks.  Freezing temperatures make this even worse – the expanding ice will lift and crack the roofing material.  Clogged gutters can also become so heavy that they buckle or break.

Another key maintenance issue involves unwanted freeloaders – namely moss and lichen.  They are common on asphalt shingles where the rough texture holds tiny amounts of rainwater and provides a surface for the airborne spores to set down roots.  Moss and lichen grow especially well on cooler, north-facing surfaces.  As the plants develop, they lift and crack the shingles.  To prevent this, homeowners can spray on diluted bleach or chemical moss killers and also install strips of zinc near the top of the roof.  Each time it rains, small amounts of zinc cascade downwards inhibiting the growth of moss and lichen. 

Metal roofs are typically not hospitable to moss and lichen because of the smooth, hard surface.  That being said, these plants are tenacious!  It is wise to occasionally wash the roof to remove any dirt where the plants could become established.

It is important to note that the signs of a leaky roof, such as mold, ceiling stains and structure damage, can also be caused by interior condensation.  At the first signs of trouble, homeowners should investigate both possibilities.  Condensation can develop when there are problems with the heating and cooling system and/or inadequate insulation in the attic.  Interior moisture issues are made worse by frequent rains.  A qualified contractor should check both the roof and attic. 

A solid, well-maintained roof is a protective umbrella over a valuable asset.  A small investment of time and money on maintenance and inspections will pay off with years of protection and peace of mind.