re-roof question


Old 02-17-11, 04:21 PM
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re-roof question

I have to re-roof my house this spring. Its a 4/12 asphalt shingle which it will be replaced with. I'm sort of going back and forth about doing it myself or just hiring someone. I live in the pacific northwest so tons of rain (I mean tons we are in a rainforest) and some snow. I'm going to have to re-sheet the back half of my roof due to ice damming damaging the sheeting underneath. I'm thinking a combination of things led to this. All the pipes vents bathroom vents etc come out the back half generating heat in the attic and it's the north facing side of the roof so less sun combined with a really cold winter and not enough roof vents.....

Here is my question. Both local roofers quoted me 1 roll layer #30 paper on the bottom of the roof and one layer #15 above that with all new vents. Is that sufficient? What kind of extra cost would a membrane cost to do on the bottom and should I do one roll or two up the roof? I think the rolls are about 2.5 feet wide and we are talking about 50 ft. If its only a hundred or 200 more bucks to just membrane the bottom back half of the house I'm okay with that...

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Old 02-17-11, 04:48 PM
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I dont know about all the stuff your talking about and cant help there but what I feel you should do before anything is figure out the proper ventalation. This is what causes the ice dams.

Ridge vent, soffit vents, gable vents, insulation?????? Fix that then concentrate on roofing materials.

Understanding and Preventing Ice Dams on the Natural Handyman home repair and do it yourself website

My 2 cents

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Old 02-17-11, 05:21 PM
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I agree about the ventilation to prevent ice damming. I also say you would be a fool to not do a water and ice shield given the history of your problem. Felt paper just isn't going to do the job.
Old 02-17-11, 05:34 PM
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Thanks guys Yes I sorted out the ventilation issue already. I have enough soffit vents but not enough roof vents so I replaced a couple roof vents with turbines and that did the trick. Lots of wind in the winter here so when the weather is crappy and you might otherwise get damning the air is flowing through the attic.

The roof had been on for at least 15 years with no issues but we had a particularly harsh winter here and it hit -15 Celsius daily for two weeks which happens maybe once every ten years....

So back to the membrane. How far up the roof should I do?

Old 02-20-11, 06:33 PM
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If you are having ice dam problems 15#or 30# felt is not going to help out the situation. The rolls of 15# or 30 # felt are 3 feet in width. I would recommend using ice and water shield on the bottom of your roofs. Ice and water shield comes in 3 foot wide rolls that are one square or two square each. The ice and water shield should be installed a minimum of 18 to 24 inches past the interior wall line going up the roof. The remainder of the roof should have 15# or 30# felt installed before the shingles are installed. Another good thing to check into would be Ridge vent versus your regular turtle vents.

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