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Rolled roofing or shingles?


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04-20-17, 01:02 PM   #1 (permalink)  
Rolled roofing or shingles?

Redoing a screened in porch after 30 years (not a 3 season porch). Porch is off the back of the house with floor to ceiling screens on 3 sides. Roof is about a 2:12 pitch roof or ~9.5 degrees slope. Ice dams are not a problem given it is not an enclosed porch.

Existing roof is a rolled roof. I would prefer to replace it with 3 tab shingles for longevity, but also want to use the right product.

Will either a rolled roof or shingles be ok for this roof?

Or, is there a reason I need to use a rolled roof in this application? For example, might it be more prone to leak?

Possibly the manufacturer will not warranty shingles if the pitch is less than 2:12? Or ?

Signed,

Roofing novice.


Last edited by jdbs3; 04-20-17 at 01:17 PM.
 
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04-20-17, 01:41 PM   #2 (permalink)  
Alright, I've been reading everything I can find, and it looks like 3 tab shingles is not the way to go.
From a google search "shingle roofing is not watertight, in the sense that standing water—or wind-driven water on a low-slope roof—can work its way up between the laps, which is the reason for the minimum 2/12 slope."

And "the only function the three tab shingles perform at that low a slope is decorative". This is not an issue for me; as is the porch is close to the tree line, so one needs to stand way back to see it.

and ice dams are not an issue.

So let me change the question. Given all the information provided, what is the recommended roofing material - rolled roofing, or some type of rubber roofing like EPDM, or is rubber roofing overkill for my application?

Thanks in advance for the comments.

 
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04-20-17, 03:13 PM   #3 (permalink)  
Steel or other metal roofing. Your slope won't work with shingles due to capillary action Rolled roofing is being replaced for a reason, and a better product is metal.

 
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04-20-17, 10:32 PM   #4 (permalink)  
You don't say where you are, but out here in AZ, I believe a torchdown or EPDM is very common. They coat it after with some sort of white reflective solar coating. The coating can be renewed every 5-7 years. Just scrub the old stuff with a deck brush, let it dry, roll on a new topcoat.

Had it at my old place on the back patio, at least 12 yrs old, never recoated, and didn't leak a bit.

This place has a patio with shingles, the whole roof can't be more than 5-7 yr's old based on condition. Patio leaks like a sieve and there are stains and rot in the rafters. Why they didn't put a better roof on when the house was re-done, I'll never know.


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04-21-17, 08:09 AM   #5 (permalink)  
Location - Greater Boston area.

Shingles are out. Given it is only a screened in porch, a metal roof feels like overkill; ditto EPDM rubber roof.

I am leaning toward just rolled roof as is on there now. However, I want to avoid leaks for as long as possible.

What installation suggestions would folks suggest to assure it does not leak for as long as possible?

thanks

 
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04-21-17, 01:42 PM   #6 (permalink)  
I'd do a larger than normal overlap, with roofing cement on the upper edge of the lower sheet(s). Be sure to plan for flashing where it meets the house.


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04-21-17, 02:38 PM   #7 (permalink)  
Roofs that are 2:12 to 4:12 are considered "low slope" by roofing mfg's. They have special instructions for the underlayment only. The shingles are applied normally. Most mfg's recommend a double layer of underlayment.
First row is 19" wide. Next row completely covers it. Next row overlaps 19" so you have double coverage.

Lapping more than normal or using tar are not part of mfg's instructions.

I would use a laminated metric shingle, not 3 tabs.

I know some guys who swear by using ice and water shield as the only underlayment on the entire roof when its low slope, but you won't find that in mfg's instructions either.

And you should never use shingles on a roof that is less than 2:12.

 
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04-21-17, 02:46 PM   #8 (permalink)  
Brant......thoughts on using Titanium as an underlayment rather than tarpaper? It self heals.

 
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04-21-17, 03:21 PM   #9 (permalink)  
Yep, Titanium PSU-30 is like a ice and water shield... "Designed for 2:12 or greater sloped roof applications subject to the effects of ice damming and wind driven rain." -per their instructions. (http://www.bestmaterials.com/PDF_Files/PSU-30_INST.pdf)

 
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04-26-17, 12:08 PM   #10 (permalink)  
Thanks to all for your feedback.

XSleeper - Most mfg's recommend a double layer of underlayment ...
Okay, I will use a double layer of felt underlayment installed as you suggested.

I plan to use lap cement and the concealed nail method for installing the rolled roofing.

I read in one forum thread, that for a < 2:12 (I believe mine is just under 2:12), I have to go with 19" selvage edge roll roofing for double roofing. I would then have 4 layers with the double layer underlayment.

1. Does the double underlayment negate the need for the 19" selvage edge rolled roofing? Possibly it is best anyway.

2. If I can not find 19" selvage edge rolled roofing, is it okay to use the normal rolled roofing, and just overlap it by 19"? The reason I ask is that the overlap would then be ~15" lapped over the area with granules. Is this an issue?

3. And would #30 felt paper add any benefit over #15 for minimizing future water leakage?

4. Another update - While pricing felt underlayment at my local big box store, I read about Grace GRACE TRI-FLEX® High performance roofing underlayment. It would also be installed half lapped a full 24" for double coverge. The reviews on Lowes were all 5 star. The cost is $113 vs $18, but it would appear that this is a step up from the #15 felt. Would you agree that this would be better for minimizing future water leaks?

And yes, I understand none of these product will assure no water leaks. I'm just trying to extend the roof life from an average 3 - 5 years for rolled roofing to a few more years beyond, and make it easier to re-roof it next time by just replacing the rolled roofing.


Thanks again for all the help!


Last edited by jdbs3; 04-26-17 at 12:54 PM.
 
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04-26-17, 02:51 PM   #11 (permalink)  
Get a 4' level up there.... hold it level and measure down to the deck. At 48", a 2:12 roof would have 8" vertically between the roof and tip of the level. No point guessing.

If its 2:12 or greater (8" of drop or more in 4') I would use shingles not roll roofing.

Yes, #30 equals 2 layers in my book. But if you do a poor job felting and get ripples in it, or if it rains on it, #30 wont lay down very flat. Those ripples telegraph through to the surface of your roofing.

 
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04-26-17, 07:40 PM   #12 (permalink)  
Can you please share what is the name of the coating? I have a torchdown flat roof that needs to be repaired/replaced and then coated with something reflective imo.
Actually just found this one at HD silicone based -
Henry Tropi-Cool 4.75 Gal. 887 White 100% Silicone Roof Coating-HE887HS073 - The Home Depot

Would/should this work on 5yo flat roof?


Last edited by Newbie; 04-26-17 at 08:30 PM.
 
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04-27-17, 08:49 AM   #13 (permalink)  
And another viewpoint ...

Pitch was checked - it was 9" with 4' level, thus 2.25 : 12.

I was leaning toward Grace Tri-flex, but then read the following (see quote below).

A major goal is to avoid water leaks as much as possible. So should I go #15 felt double lapped, or Grace Tri-Flex?

and

I'm still leaning toward rolled vs. 3-tab, but if I go rolled roofing and can not find 19" selvage edge, is it okay to use the 2" selvage and just overlap it by 19"? The reason I ask is that the overlap would then be ~15" lapped over the area with granules. Is this an issue?

Thanks

Synthetic underlayments are inferior to felt paper products due to their low permeability. Even though shingles have a low permeability felt paper creates a buffer zone between the wood decking and shingles ensuring the wood deck remains dry. This is very useful in ensuring new wet lumber installed as roof decking can release the excess moisture. Having two low permeabile products on top of one another is never a good idea and is not a practice followed by elite contractors. Felt paper also absorbs liquid water and wickers liquid water away from the wood deck helping to keep the wood deck dry due to liquid water penetration. Paper will hold the excess water allowing it to evaporate through the roof ventilation. Synthetic underlayments do not absorb any water and do not wicker moisture away from wood decking.
Wrap a wet piece of lumber[osb for quicker results] completely with felt and another with synthetic underlayment. Leave it for a year and unwrap and you will witness the superiority of felt paper.

 
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04-27-17, 01:28 PM   #14 (permalink)  
XSleeper,

Given the quote in my last reply (not from you), and this quote from you back in 2012 (see below), you can see why I am confused on felt vs Grace Tri Flex underlayment.

Tri Flex has a perm rating of .54, roof felt has a perm rating of 5. Possibly this is a "religious" argument about which is better to use for a screened in porch.

If I am not really getting any benefit from the Tri Flex, then good old #15 felt (2 layers), probably makes more sense.

And there is still the question from my last response of whether it is okay to overlapp by 19" the 4-selvage rolled roofing.

Time to start the work, so any last feedback is appreciated.

Thanks!!

Grace tri-flex has a perm rating of .54 and thus is a vapor barrier. As such you do not have to worry about the moisture of wet shingles getting to the wood sheathing and casing any problems... it will force the roof to dry to the outside. If the shingles are wet they will likely dry out quickly when exposed to a little sun and wind. Shingles are not air tight even when sealed down so they will dry out just fine.

 
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04-27-17, 04:26 PM   #15 (permalink)  
You said this is a screen porch, so the vapor barrier issue is completely pointless and is nothing to worry about or even consider. I'm also not up on rolled roofing and even if I was i would not recommend or use it. Your roof is over 2:12... it is fine to use shingles, (but do not use 3 tab, use a laminated architectural shingle, it has better coverage) so that is what I would recommend, period. It will not leak.

You are over thinking the underlayment.

 
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