New Roof Over Old Roof or Not?

[MelvinSlankerd]

the house I bought has 5 layers of roofing. Doesnt' leak a bit. The last one applied was at least 30 years ago.

[Tony]

Comments inserted

Wrong. You are apparently not familiar with ice dams at all. Felt does absolutely ziltch for protection against ice dams, you must use a water & ice guard which is manufactured under several names.

Yeah, don't use felt if you want the back of the tar strip to stick to the decking. Felt is layed for a purpose other than a dry in feature as you suggest.

[Phisherman]

Much better to tear off the old shingles and tar paper for two good reasons. One, the roof can be inspected easily for any damage. Second, there is less weight on the roof (shingles are heavy!). Consider adding a ridge vent if you do not have one.

[Tom]

Comments inserted as well. Tony wrote:>Wrong. You are apparently not familiar with ice dams at all. Felt does

Sounds like you work for W.R.Grace, a major supplier of bituminous membrane. Being from Michigan, I'm _very_ familiar with ice dams, and with the latest and greatest of ice and water shield technology. A double coverage of 30 lb. felt installed up only 3 feet beyond the inside wall will stop an ice dam from penetrating the decking perfectly well, and cost less than the modified bitumin (tar). >Yeah, don't use felt if you want the back of the tar strip to stick to the

I suggest you look at a shingle to see if there even IS a tar strip on the backside. Felt is laid just for the reasons I stated. Hope this helps. Tom Someday, it'll all be over....

[Ralph]

Grace is garbage, being familiar with the latest technology you should know this and not bring that name into the subject. You are 100% wrong in assuming double coverage felt will stop ice from creeping under it. That statement is laughable even by those that don't know much about roofing, those with a little common sense would even know that. I take it you're one of those weekend warriors, since your knowledge is lacking.

I suggest you look what is holding the cellophane on the back of shingles, guess what that substance is? And yes the tar strip melts when heated, and creeps from under the cellophane, which in turn sticks to the felt or roof deck if felt is lacking.

If you need any knowledge you want to pass on, so you don't look like such a fool. Just ask and you shall receive. No charge for roofing 101 course today.

[Leo]

I believe Ralph paid you a compliment calling you a weekend warrior. Where I'm from we would call you the local hack.

FYI, you left out the most important part of ice and water shield. It adheres to the deck, where as felt doesn't. I don't care how many layers of felt you put down, it will not shield decking from ice backup. Ice & watershield also seals around nail heads, NO felt made will do this.

You sir are a true hack.

Look again Mr. Hack.

[Tom]

Ralph wrote:>Grace is garbage, being familiar with the latest technology you should know

Well, enlighten me. Grace was the first stuff I saw come down the pike, and serviceable but slippery it was. However, I've been out of the business for about 10 years, so whatever's happened to their reputation is a mystery to me. That little piece of cellophane on the back is only there to keep shingles from sticking together in the bundle. and I don't believe it would creep at all when the roof heats up. Again, I've torn off a few roofs, and might have missed looking for the "creep", but all that was holding the shingles down were nails or staples. Unless some fool used tar behind a chimney or something. Perhaps the words "perfectly well" (referring to felt stopping an ice dam) were the wrong ones to use, (just how fast will a nail leak through 30 lb.doubled? (Rhetorical question.)) so I'll say "darned well". But how soon we forget the ways things used to be done, and done successfully. If the causes of ice damming are left untreated. the eave shingles will experience something like "frost heave" over a number of cycles, rapidly accelerating their degradation. A properly ventilated/insulated attic _needs_ no_ barrier_ at_ all_. Sorry to have ruffled your feathers, but I've installed machine-cut cedar on pitches as low as 6/12 with no barrier, and no damming . Perhaps with today's shoddy/cheap builders, the first roof probably _needs_ a barrier, but by the time you find out, the damage is done. Damn I'm long-winded. Again, sorry to have ruffled. Tom Someday, it'll all be over....

[Tom]

Leo wrote:>I believe Ralph paid you a compliment calling you a weekend warrior.

Well, the thick skin helps a little. I guess. Here we go... Whether something "adheres" to the decking is irrelevant(unless you're trying to tear it off. Ever tried to tear off the sticky stuff?). The only thing holding your roof on is nails or staples, and the weight of the entire field stuck together just under the tabs by the tar strip.(Otherwise, those shingles wouln't be so easy to cut out and replace!) Of course the membranous stuff will seal up better around the fastener, isolating the homeowner from interior evidence of the ice dam. "If it's not leaking, no problem". So they forgo fixing the causes of ice dams, and when that underlayment starts to see daylight, you've got problems. Same with felt, also. Doing it right doesn't have to cost too much. I know of cities where you're _required_ to use the sticky stuff and I wonder about that. But it's great for when the architect is on something, and designs a bathtub in at the bottom of a valley. Tom Someday, it'll all be over....