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Q I know I need to replace our cracked and worn shingles. The local code allows me to add a second layer of shingles, but I’m told by a roofer buddy that it’s better to strip off the old shingles and start with a clean slate. Otherwise, he says, the new shingles will wear out quicker. What do you think? What’s the best method?
A Although there’s anecdotal evidence that new shingles installed over old shingles won’t last as long as a single-layered roof, most manufacturers offer the same warranty for both methods. However, if you are planning to keep the house for the long term, we suggest ripping off the old shingles so you can:
- Find out what’s been happening under that blanket of old shingles. Small leaks can cause big damage in underlying roof sheathing and framing. It’s easy to find and fix damage when you expose the roof surface.
- Replace damaged or corroded flashing and metal valleys.
- Install ice and water barrier to prevent ice dam problems.
- Have a new roof that’ll look much smoother on a flat surface than it would have on old, wavy shingles.
Tearing off an old roof is a big job, but if you invest in a few specialty tools, line up a crew and a trash container, and get your ducks in a row ahead of time, the work will go much faster. You’ll most likely be required to obtain a building permit, so visit the building inspector before the job starts.
Order a trash container to hold everything you tear off (a 20-cu.-yd. unit will take care of the average 1,500-sq.-ft. roof). You’ll save tons of time if you instruct the driver to position the unit under an eave so you can dump directly into it. Be there when it’s dropped off to get it where you want it. A trash container runs about $300 for five days. If you hustle on installing the new roof, you can throw in the new shingle wrappers and leftover shingle cut-offs, too.
Pick up felt paper, ice and water barrier and wood lath (to help felt paper stay put in the wind) so it’s on hand the day you start the tear-off. Then you’ll be able to waterproof immediately and snap the chalk lines for laying out the new shingles before the roof is cluttered with new shingle bundles. Order the shingles for delivery the day after you expect the felting to be finished. If you do that, the supplier can lift the shingles right to the roof for easy staging.
Three hardy people can tear off and felt a roof in one day, but be careful. Only tear off what you can safely protect from the weather the same day, especially if you’re working shorthanded. It always takes longer to weatherize than you think! Tear off the areas farthest from the trash container first. That way you won’t tear up the new felt paper when you haul the rest of the debris to the container.
Go over the wood surface with a fine-tooth comb after tear-off. Pound in protruding sheathing nails and remove any leftover shingle nails, then sweep and install ice and water barrier and felt.
Working On A Roof - Safely
Many professional roofers don’t use safety harnesses, but they’ve got experience on their side to help keep them out of trouble. (Some are even blessed with prehensile tails.)
Weekend warriors should follow these commonsense safeguards:
- Wear safety belts and ropes-especially on steeper slopes where the footing is dicey.
- Extend access ladders a few rungs above roof edges and ballast the bottom with a bundle of shingles to prevent kickouts.
- Avoid working on frosty or wet roofs.
- Be aware of overhead power lines.
- Nail down 2x4 “kickers” near well-traveled roof edges like shingle unloading points or dumping stations.
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