The methods for tying in and flashing various roof penetrations and structures are similar for an over-lay or a tear-off. The difference is that the overlay often requires only the final few steps of the several that would have been required if you were working on a complete tear-off (or new roof).
If you are overlaying your roof, it is helpful for you to know what is underneath your old shingles. The knowledge of how the work was done originally will help you understand why you are doing certain things on your overlay.
Let’s review the reasons an old roof should be torn off:
1. There are already two complete roofs on the house, the original plus one overlay. If your home is in the forty-year age range, chances are good it already has two roofs.
2. You only have one roof, but the shingles are badly curled and crumbling.
3. Inspection from inside your attic reveals extensive deterioration of your sheathing and/or rafters.
4. There are multiple problems with the roof, including poor workmanship and waving, erratic alignment of the shingle courses.
5. You only have one roof but it is done in dimensional shingles. Dimensional shingles simulate the coarse texture of cedar shakes and don’t have an even surface for you to overlay.
There is too much work, risk, and mess for even the most extreme perfectionist among us to do a tear-off because, “It’s the way to really do the job right.” If your roof doesn’t need to be tom off, a well-done overlay is great.
My number one rule for a tear-off is: never begin a tear-off until all your materials are stocked on the job. There is a story behind this rule. My main supplier was absolutely and completely reliable. My materials were always on the job on time or early, except once. That one time he promised me absolutely that the shingles would be there by midmorning. I started tearing off the rear roof of a customer’s home. There was still no sign of my supplier at 10:00 AM so I called him. One of his drivers had called in sick, but everything was okay. By late morning the rear half of my customer’s roof was gone, and black clouds were rolling in despite the forecast of perfect weather. I called my supplier again. One of his trucks had broken down and his third truck was stuck in the mud on a new construction site. That stuck truck was the one that was supposed to bring my supplies to me. My materials were still sitting in his warehouse. I dumped the bed of my truck in the customer’s driveway and dashed through heavy lunch hour traffic across two counties and picked up my “delivery.” My crew had been sitting idle for two hours when I got back to the job.
We got the No. 15 felt down over the plank sheathing just as the rain hit. Fortunately, it wasn’t a blowing rain.
My risking a tear-off before all supplies were on the roof almost led to a disaster, but you can learn from my mistakes. I don’t care what promises, commitments, time constraints, or whatever else you have, don’t tear off until everything you need is sitting there ready to go.
Since you are new at this, pick the smaller and easier section of roof for your first tear-off. If you are reroofing your house and detached garage, start with the garage. Ease yourself into this tear-off so you develop a feel for it.
If you have a section of roof with no valleys, sky-lights, chimneys, etc. and it also is the farthest roof from your dumpster, truck, or trash pile, start there.
By going to the most remote site and working toward your trash pile or truck, you won’t have foot traffic over a new roof and run the risk of scarring it.
You can tear a roof off using a square shovel if you want to. It gets under the shingles and will pry them up and pull most of the roofing nails out too. Better tools are available. A shingle stripper (roofing spade) is a narrow square shovel with large V-notch teeth cut in the front of the blade. The teeth will go under the head and around the shaft of a stubborn nail and make it easier for you to pop it out. A pipe is welded across the upper back of the blade so that when you push the handle down, the pipe acts as a fulcrum and gives you leverage to pop the nail out. A short handled shingle stripper is best on a steep roof (greater than 8/12). It lets you work right beside where you are leaning against the roof. A long handled shingle stripper is best on a moderately steep roof (6/12-8/12); it lets you reach farther.
There is a tool called a shingle eater that has a wider blade, a sharp upward angle at the rear of the blade to act as a fulcrum, and a metal handle that is bent upward. The sharp upward bend of the handle saves your back by letting you stand more erect as you tear off a 4/12 or 5/12 roof.
It depends on your preference whether you want to buy these specialty tools. You can do the same job with a square pointed shovel and a claw hammer it just takes a lot more effort
METHOD OF TEAR-OFF
If your sheathing is plank, cover anything valuable in your attic. Grit, nails, scraps, and dirt are going to fall through the gaps in the plank.
Start your tear-off across the ridge from the roof you want to remove. Insert your stripper beneath the bottom edges of the shingles two courses down. Pry these shingles up and keep working your stripper up toward the ridge of the roof. Come on across the ridge, prying the caps up and free. Throw all the old caps and shingles in your truck or trash pile. Now you are ready to start down the side you are going to tear off. Get your stripper under the/e/? And start prying the felt up along with the shingles as you work your way back and forth across and down the roof.
Some roofers like to tear off coming up from the bottom of the roof. Tearing off going down the roof gives you bigger chunks of roofing that don’t separate into individual shingles. Going down the roof helps keep all the scraps, grit, and nails down below you while you keep good footing on fairly clean sheathing.
Nail: Some roofers try to talk the customer into reusing the felt from the original roof. They will very carefully tear off the shingles only. Reusing the old felt saves the cost of the new felt. Since the original roofer’s old lines will still be visible, it also saves the time it takes to mark the courses and verticals (base and offset lines). The old felt won’t act as a backup roof. It will turn away about as much water as Swiss cheese.
Your supplier may have stockpiled shingles on the ridge. Don’t try to move the piles; just tear off around them. You want to move the bundles in this pile around as little as possible. You want to move the bundles from the pile to where you are going to use them. You don’t want to double your work by moving the whole pile to another location on the roof and then later have to bring the bundles back to where you are going to use them.
Keep your nails and grit swept off the exposed sheathing as you go. The trash can be as slick as ball bearings. When you get to the bottom of the roof let the trash fall into the gutters as you roll the tear-off material into large chunks.
Be especially careful to keep a clean footing along the bottom of the roof. (A wide shop-type broom works well on a roof.) I only had two men fall. Both times they were tearing off. Both times they were at the bottom of the roof. Both times the roofs were 5/12 (safe). Both times the men had let the trash accumulate under their feet. Neither man thought the grit and nails would throw them. Neither man had time to yell before he went over the edge. Both men were lucky. One fell in a dense thorny bush which broke his fall, but he looked like he had been attacked by fifty furious cats. The other man landed on a concrete walk and only lost a little time from work. He was bruised and stiff for days. Both men were very careful about keeping the roof clean after they fell.
You will snag and pull some of your sheathing nails no tp« r\ff Once von have swept the roof clean, drive down or replace the sheathing nails. You also may need to add nails that the carpenter missed on the sheathing when your house was built.
Nail: Some roofers don’t replace the sheathing nails they pull out or go back over any of the original carpenter’s “skips.”
If there is rotted or broken sheathing, replace it. You will find that when a sheet of plywood has a rotten spot, it is easier to tear the whole sheet out and replace it with an entire new sheet. Cutting out and removing a part of a sheet and then fitting a new piece back in is tedious and time consuming. If the rotten sheet had cutouts for vent pipes and such, use your old sheet as a pattern for the cutouts on your new sheet.
If there are major breaks in the plank sheathing, replace the plank as necessary. Plank sheathing may have broken due to a large knothole, or one of the planks may have cracked. If the hole or crack isn’t huge, cover the hole with a metal patch. Cut a length off your aluminum coil and nail it over the hole. (An old piece of galvanized metal is good for this, too.)
You are covering the hole to keep someone from stepping down into the hole and punching a hole through the new shingles in the future. The metal patch is an acceptable repair, and you can roof right over it.
Nail: On one tear-off, I discovered a 10-inch diameter hole in the plywood sheathing. The hole was either cut by mistake, or the plans were changed and the furnace, with its metal chimney, was relocated.
Anyway, the original roofer laid the shingles right across the hole, with no metal patch. I was glad I hadn’t stepped on that particular spot.
If your plywood sheathing has sagged between the joists, cut a 1472-inch or 2272-inch piece of 2 x 4 to fit the space between the joists. Pre-nail a couple of angle nails at each end. Push the plywood sheathing back up even, using your shoulder against the 2 x 4 cross brace, and nail the 2×4 cross brace into place.
Once you have the cross brace angle nailed, you should end-nail the brace. Go to the sides of the rafters opposite the brace and nail through them into the end of the cross brace.
If at all possible, get in the attic early in the morning before it gets too hot. If a rafter has sagged badly, loosen and raise the sheathing to push the roof surface back into shape. Push the sheathing up with a 2 x 4 that spans the length of the sag in your rafter.
Face along the top of the rafter with the new 2×4, which you nail in place in its raised position across the length of the sag. (One person can do this, but it’s far easier with two.) This will get rid of the dip that showed in the roof.
Face any broken rafters with 2 x 4’s nailed on both sides. If a rafter is somewhat dry-rotted and is question able, face over the dry-rotted area with a 2 x 4 on one side of the rafter. Make sure your 2×4 spans over the rotted area and is nailed into good wood.
If a rafter is truly rotten, face one side of it with a 2 x 4. Remove the sheathing above and cut out the rotten section of rafter. Face the opposite side of the gap in the rafter with another 2×4 and restore your sheathing.
Once you have tom off, getting a roof back on your home is your number one priority. No. 15 felt does a pretty good job of waterproofing plywood sheathing. It doesn’t waterproof plank sheathing quite as well. The problem with plank sheathing is that you are going to hit the gap between the planks with your swing tacker and tear a hole in the felt. Consequently, felt on plank turns most of the water. There is almost nothing you can do about it except push yourself to get the new shingles laid. There is one other thing you can do, but it hurts my pride even to say it. Polyethylene sheets spread over the insulation in the attic are a good backup system if you have just felted in the plank sheathing and have to ride out a storm.