layover roof questions

Old 09-21-04, 03:43 PM
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layover roof questions

I have a 4/12 pitch roof that had two layers of asphalt shingles on it. I have ripped off one layer of shingles and the layer that's left is old and lost most of its grain but it is laying flat and is in tact for the most part. It has a bit of heavier deterioration down by the edge... probably caused by ice/snow.

I'd like to lay some ice-dam rubber material along this edge right over the old shingles and then felt the roof as well... like it was a new application. Then lay the new tiles over that. Is there any reason not to proceed this way... laying the rubber and felt right over the layer of old shingles?
Old 09-21-04, 07:36 PM
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Why didn't you just tear everything off? down to the roof sheathing? Seems like a lot more work to pull just on roof layer off.

If i want something done right I do it myself so since you're doing it yourself why not tear everything off? I guarantee it'll take less time than it took to tear the one layer off.

Just get a pitch fork and use that to get under the shingles & paper.

This way you can do the roof right by putting drip edge along the eaves and rakes. Then put the ice shield down along the eaves and paper over the ice shield all the way to the top.

To start the 1st row of shingles all you do is run a row of shingles along the eave turned upsidedown so that the tabs are pointing to the peak. Then you put the first row of shingles down as you would normally do.

Another hint. Get some traps and lay them on the ground below the roof. Let the tear off land on the tarp and when it's time to clean up just pull the tarps away from the house. Back a trailer up and bam clean up is simple.
Old 09-21-04, 08:26 PM
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I didn't go down to the deck because I wasn't supposed to be doing *this* roof at all in the first place. I'm actually working on the attached two-car garage roof which I *have* taken down to the decking boards.

The garage roof joins the roof in question (a 50's addition connecting the house to the garage) and as an afterthought I decided to pull off a layer of roofing so I can lay the same new roofing on both structures... for aesthetics.

I don't want to take off the second layer of roofing because on one long side it butts up to the house which is covered in 50 year old hand-split cedar shakes and I don't want to get into pulling off siding to redo the step flashing along that wall. The siding is impossible to find in affordable quantities and it's very brittle. I can just see the can of worms waiting to be opened.

So my question remains... can I treat the remaining layer as I would a bare deck and ice dam/felt over it before putting on the finish layer of roofing.
Old 09-21-04, 08:31 PM
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Oh and it wasn't more work. The first layer came off in huge chunks just pulling it up by hand. I didn't even use any tools. This was, no doubt, because they used short nails that didn't reach through the old roofing and into the sheathing

On the other hand they did go through the trouble of nailing down each and every tab on the old roofing before laying the second layer... it would be a real pain to pull it off... and get all those nails out!
Old 09-21-04, 11:49 PM
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Ok I understand now

The purpose of base felt is to provide a vapor barrier between the sheething (roof deck) and shingles. The purpose of ice shield is to protect the sheathing from damage casued by ice dams.

So you wouldn't be hurting anything by putting these over shingles. You'll just be wasting time and money.

Here's what I'd do if it were my house. I'd tear the old roof off. This way I could put drip edge and ice shield down.

If the shingles butting up to the siding is what maybe keeping you from doing this maybe I can shed some light.

First, shingles shouldn't butt up to the siding. Siding laying onto roof sheathing is a recipe for rot. there should be 1/4" - 1/2" gap between the siding bottom and sheathing. Flashing tucks up behind the siding and the shingles butt up to the flashing. So the shingles actually slide under the bottom edge of the siding.

Now if your siding is touching the sheathing then it should be cut back so there's a gap like i mentioned above. Cutting cedar shake is easy. You can score it with a utility knife. If your cedar siding are panels then it'll be somewhat more laborous.

First either snap a chalk line to get the gap or attach a straight edge (3/4" or thinner stock) for the utility knife to follow. A staright edge isn't permanent and thus no need to nail the heck out of it. The straight edge is just a guide. Attach it with a small nail, like a 4d nail. Don't drive it home, leave the head up so you can pull the nail. cedar is resilient. A small nail hole in cedar will close up in time.

Staples would be ideal if you have access to a staple gun, pnumatic of course. Then just pry the straight edge off at one end and then grab the board and pull it off.

If your cedar shake are panels then snap a line to follow. Use a hammer and a sharp chisel. No need to go all the way thru as they should break by prying out at some point.

Now we just need to prepare the siding to install flashing. You don't need to pull siding off. When we build houses we don't nail the bottom of the siding. We just start the nails and the roofers drive the nails home after the flashing's in. This way it keeps the roofers from screwing up the siding as they put the flashing in and keeps us from coming back to make repairs

All you need to do is remove the bottom nail. Then you should be able to pry the siding towards you enough to slip the flashing behind the siding. Who knows? Maybe you won't need to remove nails.

To remove nails you'll need either a flat bar or nail puller (more commonly know as a cat's paw). A flat bar isn't flat as it has a camber to it along with a hooked end. It's made out of flat steel stock.

Notice each of these have a groove where a nail can go. All you need to do is rotate the bar up behind the siding so the nail's in the groove. Then just pry back a little. After you see the nail come out a little remove the bar from behind the siding. Then beat teh cedar shake back against the house. now the nail head should be exposed enough to pull it.

Caution!! Pry back slowly so you don't break the cedar. When you beat the cedar shake against the house, use a scrap piece to prevent hammer marks.

Now you should be able to pry the siding away from the wall to tuck flashing behind the siding. Again pry slowly and be careful.

When nailing siding use galvanized or stainless steel nails. All nails exposed to the elements should be either of these since they won't rust like iron nails.

Good Luck!!

Oh yeah, after removing the roof you don't need to remove all the nails. Just pound them down.
Old 09-22-04, 12:00 AM
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Dam I wish they had the entire thread on the reply page

If the shakes seem brittle you can hose them down before you start. Soak them. Then soak them again before starting to work on them. If you have a hand sprayer this would be good to use after the roof is off. Or just put a tarp down or some felt. The idea is to get the shingles soaked to make them less brittle.

Yes water does make wood less brittle. Woodworkers steam wood when they need to bend wood. Google for wood steamers hehe
Old 09-22-04, 12:07 AM
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Oh yeah...if you do break a shingle or 2 or screw up, you can always get a piece of rough sawn cedar and put a trim board at the botton. The siding bottom should should butt up to the trim board. So you could cut the siding back the width of the trim board plus the gap if one is needed. Then the flashing will tuck behind the trim board.

Depending on your saw and the width of the trim board, you might beable to cut the siding back by snaping a line and setting the depth of the saw to just barely cut thru the cedar shake.

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