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-   -   Replace valley (http://www.diychatroom.com/f9/replace-valley-153476/)

Malcolm 08-12-2012 10:25 PM

Replace valley
 
I am debating on how to fix a closed valley on a 2/12 pitch roof. The entire roof will be replaced within the year. I'm doing this for a relative. She has limited funds at the moment. Should I go through the expense of putting down ice and water and metal flashing, or should I just go with one or the other? I am even contemplating just replacing the shingles, since it will be replaced soon.

I'm even open to just putting plastic or using a tarp over it. I don't know if she will have the funds next month or next year. How long do you thing plastic sheeting will last (a month)? I guess I'm looking for opinions.

joecaption 08-12-2012 10:33 PM

#1 There never should have been shingles on a 2/12 pitched roof. Sure way to have a leak.

Malcolm 08-13-2012 10:04 AM

Quote:

Originally Posted by joecaption (Post 987189)
#1 There never should have been shingles on a 2/12 pitched roof. Sure way to have a leak.


3 tab shingles on 2/12 pitched roofs is the standard in my area. I've never seen anything other than that on that pitch. This is in Florida.

AGWhitehouse 08-13-2012 10:13 AM

I totally agree with Joe, 3/12 is the minimum pitch for shingles, no matter the region. Roll/sheet/standing seam roofing of some sort is for lower pitches.

joecaption 08-13-2012 10:22 AM

With even a 3-12 pitch the shingles would need to be installed differantly.
Less exposure and really should be installed over Storm and Ice Shield on the whole roof not just tar paper in my opion.
I also would never use 3, tabs on that low a slope, just asking for trouble.

Just because everyone else is doing it does not make it the right way to do it.
Check out the install directions on any shingle manufacturer and I'd bet all will say 3-12 is the bare minumum.

Time and time agin I see DIY built shed style roofs on additions with to low a slope. Everytime you will see the shingle are shot of the porch and the main roof looks fine.

Malcolm 08-13-2012 12:05 PM

Quote:

Originally Posted by joecaption (Post 987438)
With even a 3-12 pitch the shingles would need to be installed differantly.
Less exposure and really should be installed over Storm and Ice Shield on the whole roof not just tar paper in my opion.
I also would never use 3, tabs on that low a slope, just asking for trouble.

Just because everyone else is doing it does not make it the right way to do it.
Check out the install directions on any shingle manufacturer and I'd bet all will say 3-12 is the bare minumum.

Time and time agin I see DIY built shed style roofs on additions with to low a slope. Everytime you will see the shingle are shot of the porch and the main roof looks fine.

Manufacturer specifications state 2/12 is the minimum. This is with GAF and OC. The only requirement is double felt. You have to remember I am located in Florida. We do not have ice or snow. The roof lasted 15 years without leaking. 3 tabs are better for water shedding than architectural shingles.

We do not use ice and water on the eves and cut shingles flush at the eves and rakes.

AGWhitehouse 08-13-2012 01:38 PM

Quote:

Originally Posted by Malcolm (Post 987532)
The only requirement is double felt.

This is to ensure that when the shingles leak, the water finds its way back out quicker than it finds it's way in. Also note they say to only nail it just enough to hold it in place until the shingles go on. That's to minimize punctures to ensure water drainage.

The moral of the story here is, OK, you can shingle 2:12, but it's a minimalist option and for probably not a whole lot more you can roll roof it and ensure, to a better degree, water tightness.

seeyou 08-13-2012 07:18 PM

Quote:

Originally Posted by AGWhitehouse (Post 987599)
This is to ensure that when the shingles leak, the water finds its way back out quicker than it finds it's way in. Also note they say to only nail it just enough to hold it in place until the shingles go on. That's to minimize punctures to ensure water drainage.

The moral of the story here is, OK, you can shingle 2:12, but it's a minimalist option and for probably not a whole lot more you can roll roof it and ensure, to a better degree, water tightness.

I've done numerous low pitched shingle roofs installed to manufacturer's instructions. They have and will outlast a roll roofing installation. There are better options than asphalt shingles, but roll roofing is not one of them.

Also, the reason for half lapped felt (not double as stated above) or ice and water shield as an underlayment, is to guard against wind driven rain. I've perused several installation manuals and while some have a nailing schedule for the underlayment, I don't see any admonitions "to only nail it just enough to hold it in place until the shingles go on".

seeyou 08-13-2012 07:23 PM

Quote:

Originally Posted by joecaption (Post 987438)
With even a 3-12 pitch the shingles would need to be installed differantly.
Less exposure and really should be installed over Storm and Ice Shield on the whole roof not just tar paper in my opion.
I also would never use 3, tabs on that low a slope, just asking for trouble.

Just because everyone else is doing it does not make it the right way to do it.
Check out the install directions on any shingle manufacturer and I'd bet all will say 3-12 is the bare minumum.

Time and time agin I see DIY built shed style roofs on additions with to low a slope. Everytime you will see the shingle are shot of the porch and the main roof looks fine.


You need to read some installation manuals instead of betting. Also, changing the shingle exposure can void the warranty since it changes how much of the shingle protrudes past the seal strip allowing wind to lift the tabs.

Malcolm 08-13-2012 08:23 PM

I'm not going to go with roll roofing. There are a lot of 2/12 roofs in my area and all have 3 tab shingles. If there was a huge problem, they would not continue to install them on that pitch. They are prone to leaking more, but I have noticed they leak most of the time due to install error. Does anyone have any suggestions/opinions to my original questions.

Seeyou
It is called double felt in my area. I know it is half lapped, but half lapping the felt provides two layers of felt. It could be a regional thing.

seeyou 08-13-2012 09:28 PM

Quote:

Originally Posted by Malcolm (Post 987910)
Seeyou
It is called double felt in my area. I know it is half lapped, but half lapping the felt provides two layers of felt. It could be a regional thing.

I guess we can call it anything we want as long as it's done right. But there are two ways to do it: Installing two layers in full courses or half lapping. Both provide the same coverage if you slice through it, but only one is correct per the instructions.

AGWhitehouse 08-14-2012 07:53 AM

Quote:

Originally Posted by seeyou (Post 987873)
I don't see any admonitions "to only nail it just enough to hold it in place until the shingles go on".

Page 3, last sentence of underlayment instructions.

http://www.gaf.com/Roofing/Residenti...232-317-v3.pdf

seeyou 08-14-2012 02:28 PM

Quote:

Originally Posted by AGWhitehouse (Post 988237)
Page 3, last sentence of underlayment instructions.

http://www.gaf.com/Roofing/Residenti...232-317-v3.pdf


Thanks. We don't often use GAF shingles. But, it has the same verbage for 4/12 and above installations.

Edit: Also, that nailing advise is for their peel & stick ice and water shield product, not the half lapped felt. We seldom nail I&WS at all unless it's pretty chilly when we're installing it.

AGWhitehouse 08-14-2012 03:55 PM

back to the OP, I've seen tarps last for over a year before leaking. I've seen them last less than 1 month too. It really depends on the exposure (wind, rain, debris, sun, etc.) against the tarp quality and adherence procedure to the roof system.

If you're going to go through the expense of ice & water, then you might as well do it right and strip it bare and re-shingle...

Malcolm 08-14-2012 06:54 PM

Thanks

I got some advice on another forum to just use tar. I've seen other people do this. What are your thoughts on using roofing tar for a temp fix?


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