As home owners, we are all going to have to face the prospect of roof replacement on our house. It is inevitable, particularly if your house is covered with asphalt shingles. This website is intended to give enough information to be able to make some sound decisions around this subject. Since most homes are covered with asphalt shingles, I will be focusing on replacing your roof with asphalt shingles.
An asphalt shingle roof will last anywhere from 15 to 25 years depending on how the roofing material was installed and climatic conditions. Metal and wood cedar products can last longer, but again depending on installation practices and climate.
In climates with a lot of moisture, you can expect a shorter lifespan in your roofing materials. Roofing materials that remain saturated for long periods of time generally last the least number of years. Wet coastal climates can have a lot of moss build up. The moss retains moisture on the roof surface for longer periods. The same is true in climates with a lot of snow load with mild sunny winters. Snow melt from the sun will often percolate through the snow and keep the roof membrane saturated for long periods of time. This is evident usually on south facing slopes where ice dams can build up more frequently because of the snow melt. South facing slopes on a roof are typically in the worst shape. Often the north, colder sides of a roof can be in perfectly good condition, whereas the south will be badly worn out and should be replaced.
Before you replace your roof, you need to make a decision about whether or not it is actually needed and when it needs to be replaced. Start by considering the last time the roof was done and the climatic conditions I’ve described. You will need to get on the roof at some point, but you can tell a lot from the ground. Are the shingles beginning to curl at the corners? Are you seeing a lot of roofing particles coming out of your gutter drain spouts? Do you have a significant amount of ice buildup along your eaves during winter months? Is the color of your roof beginning to ‘blacken’, particularly along the bottom 4 to 6 feet?
A bit about safety. Before you climb on the roof, make sure your ladder is sturdy and well planted on level ground. The feet should be a quarter of the height of the climb away from perpendicular. My general rule of thumb is, if your knees are bumping into the rungs while climbing, your ladder is too steep. If you have to, get someone to steady the bottom of the ladder for you. Once you get to the top of the ladder and before you climb onto the roof, tie it onto your roof so that it doesn’t slip away on you. This is really critical when you’ve placed it against a metal or plastic gutter. There should be at least 3 ladder rungs above the edge of the roof.
You can see a lot just from the top of the ladder if you prefer not to climb onto the roof. The picture below shows a pretty badly worn roof along the bottom eave. The bottom eave is where you will find the worst damage. This is due to the fact that it is always the last part of the roof to dry out. It stays saturated the longest, especially where you have ice dams built up. Notice that shingle granules are missing in a lot of places.
Pay particular attention to the cut-outs on 3-tab shingles. The way 3-tab are designed, you only have one ply of asphalt shingle in the cut-outs. Technically, you only have one ply of protection with a 3-tab shingle. Once the granules begin to wash away, particularly in the cut-outs, your roof is essentially finished. If it is just starting, you might be able to make it last another year, but don’t put it off any longer than the next available roofing season.
If the shingles have shrunk so badly that roofing nails are exposed, it is time to re-do your roof. Nails that have been exposed for any length of time are always a source of leaking.
Also, while you’re at the edge of the roof, inspect underneath the first row to see if the sheathing has been wet and, as a result, rotting. Wet or water stained plywood is usually the result of poorly installed ice dam protection, no metal drip edge flashing and/or shingles poorly overhung. Ice dam build up during the winter is a result of a poorly ventilated attic. Heat loss from house radiates upwards and melts the snow from below. As the moisture drains towards the eaves it begins to freeze along the overhang of the eaves where there is no heat. Heat loss from the house results from not enough insulation, but more importantly, from gaps in the vapor barrier in the ceiling. Roof vents are an important aspect of clearing the warm air out of your attic. Does your roof have roof vents? Are they adequate? You can never have too many. Most houses I repair have inadequate or no ventilation at all.
Finally, look inside your gutters to see if shingle granules and flakes are accumulating and plugging up the drainage outlet. Check the metal flashings along walls and chimneys for rust and any gaps that expose wood, particularly if it is galvanized steel. Also, check the caulking around fixtures like plumbing and heating vents protruding from your roof. They will often be old and cracked or even non-existent. This is a common source of leaking roofs. Often, simply caulking around a chimney or plumbing vent is enough to stall the inevitable roof replacement.