Roofing install question

[anallisguy]

I have always installed roofing, whether traditional tab shingles, or roll roofing, flush and square with the drip edge and bottom edge of the roof. Around here, some roofers have the shingle extend 3-4 inches over the end of the roof and bend down into the rain gutter. Also just saw a residential flat roof installed with SBS modified where they did the same thing- let the sheet hang 3 or 4 inches over the edge of the roof. I must confess, I do not understand this. To me, over time, this single thickness, exposed to ice, snow, etc is going to weaken, leading to cracks, splits and issues. (and it also looks terrible) Can someone explain the logic behind this method of installation?

 

[Mike M]

I am by no means a roof expert ,but I have not seen such a thing in my area of Ohio.
The shingle today are made so poor most are going to metal roofs.
I can easily see that chunk breaking off and clogging up the gutters in a few years.

 

[ddbar3]

Let the shingle extend 1/2 to 3/4 on the bottem edge. I like 3/4 on the bottom. 1/2 inch going up the rake. This is done to keep the water from curling back up under the shingle.

 

[Steve@Advance]

Never seen that either. Most do extend 3/4 to 1" past the drip edge though.

The shingle mfg should have that information.

 

[1948CaseVAI]

(quoted from post at 11:26:10 10/26/17) Let the shingle extend 1/2 to 3/4 on the bottem edge. I like 3/4 on the bottom. 1/2 inch going up the rake. This is done to keep the water from curling back up under the shingle.

Yes, this is right.

 

[kcm.MN]

I learned shingle roofing back in high school, when our church hired professionals to put a new roof on. They taught me about using the 1" overhang. Was also taught that the first course was double thickness, as the edge generally gets more wear-n-tear from birds, ladders, ice, etc. That initial course was to be half-height, however.

I don't know all the arguments against too much overhang, but I would imagine the main argument against was already been stated - that the shingles simply couldn't stand up to the test of time. They are made, for the most part, to be installed on a firm surface; not be hanging out in the air without any support.

In south Texas and many other areas that do not normally see snow or ice, it's not unusual to have the absolute minimum pitch on a roof, and the overhang helps to prevent driving rain from getting underneath the roofing, then sitting there and rotting the wood out. If the wood is sufficiently protected, the water underneath can still heat up in the hot sun and turn to steam, which apparently can also shorten the life of the shingles.

 

[kcm.MN]

...I forgot to mention that I learned all this not by bugging these guys, but by learning on-the-job, as free labor. I asked, and they happily agreed.

 

[Stan in Oly, WA]

A three to four inch overhang sounds like a terrible idea to me. The 3-tab shingles on my house have an overhang of about two and a half inches, and I find that it complicates gutter cleaning quite a bit. Three or four inches would be right in the gutter, creating two separate channels and virtually guaranteeing blockages. That's in addition to the sloppy appearance and the damage the shingles are almost certain to sustain. Sometimes things are done a certain way in an area because that's just the way everybody does it. There's a story about a young woman asking her mother why she cuts both ends off a pot roast before putting it in the oven. The mother tells her that that's the way her mother did it, so the young woman asks the grandmother and gets the same answer. Her great grandmother is still alive, so the next time the young woman goes to see her she asks about cutting the ends off the roast. The great grandmother tells her that she had to because that was the only way she could get a roast to fit the largest roasting pan she had.

Stan

 

[gab]

Three plus inches don't seem right. Had a new roof installed a year ago, looks like 1/4 inch or a hair more.

 

[Dave Sherburne, NY]

My father was a contractor so I started shingling about 60 years ago and finished up about 20yrs ago. We always let the shingles overhang the drip edge 1/4" to 1/2" inch at the eaves and 1/4" on the rake. Thats the way I taught my grandsons on the last roof I ever shingled on . Interesting thing, I just read the instruction and it says the decking should be at least 3/8" thick, I never saw shingles put on plywood as thin as that. If your putting on sheetmetal, you really should read the instructions, there's a lot to learn there. If you hire someone to put on sheet metal read the instructions and keep a close eye on the guys that put it on for you. I don't think I've ever seen any metal roofing put on right. Especially on a replacement roof. Did you know there are different screws for different deckings?
certainteed instructions

 

[Stephen Newell]

I've never seen that done. It sounds like a very bad idea. If there is a gutter I let shingles overhang a little but if there is no gutter I install them flush. Someone will be putting a ladder up against the roof and a overhang is going to be damaged.

 

[MarkB_MI]

Roofers HATE to follow the manufacturers' directions! The recommendation of most manufacturers seems to be to overhang the rake drip edge by 3/8" or less, and the eave should be even with or slightly beyond the drip edge. A wide overhang looks terrible; even if there's no drip edge it shouldn't be more than a half inch.

 

[WGM]

"I don't think I've ever seen any metal roofing put on right."
Exactly! That's why most metal roofs leak. And guys who have them installed think they have a "no leak" warranty. They don't unless the manufacturer inspected it. All they have is a warranty against fade. If the material came from Menards, Home Depot or Lowes you can bet they aren't going to warranty it. Contractor warranties aren't worth the paper they're written on either. The only chance against leaks is to install a concealed fastener standing seam roof and if they are not installed right they leak also.

 

[Wheres Waldo]

I've been a Carpenter for 50 years now. a half inch is the Maximum on eaves and rakes. Last week, my son-in-law and I re-roofed his house (17 square) and stayed with that number. Menard's 'Castlebrook' 35 year asphalt roofing. I was very impressed. It wasn't cheap, but was certainly better than what was available in the 70's. That roof will outlast me; my own roof is going on 25 years now and still looks good.

 

[anallisguy]

I'll try and get a picture soon.

 

[CKain(MI)]

I am not pro, Learned how to do my own roofs, thru a pro-roofer friend. Several roofs that I have worked on, didn't appear to be make correctly. Water crawls off the edge of the single and up or in to the drip edge and down the fascia, behind the gutter..
Anyone know what I am saying.... I am not a builder, but I see that as a incorrect placement of the edge boards installed on the ends of the rafters. If the boards are put 'top edge' to top edge of sloping rafter, then it causes decking to flatten out in the last two inches. If the flat edge of shingles are not extended at least 1/2", water will not drip off well, it will run back under. So, that's one reason I have installed them about 1 " over the edge. This only applies to typical ranch style house here in Michigan, with a low pitch. Am I mistaken ??

 

[showcrop]

I noticed a few years ago that there was no water in the gutters over some doors at my church. The water was dripping down off the fascia instead of going into the gutters. When I went up on the ladder while it was raining I saw that the shingles were even with the drip edge, and that surface tension was causing the water to curl right under the drip edge and down onto the fascia instead of dripping off the drip edge This is on a fairly steep pitched roof too. In order to correct this situation I cut pieces of flashing and pushed them up under the bottom course of shingles. So I will make the observation that if you want the water to drip off the drip edge instead of running down your fascia, your shingles need to extend beyond the drip edge. The amount would depend on roof pitch. Anywhere from 3/8 to 3/4.

 

[Hoenes]

3 is too much. 1/2 is not enough. 1 1/2 is about right. The sun will curl them down just enough to turn water into the gutter instead of behind it. (Talking bottom edge only) My roof has seen 15 years, and bottom shingle has not cracked or deteriorated.

 

[oliver power]

As a professional in the field, I'll tell you what's going on. As others have said, water is following the drip edge (water retention) around, and between the gutter, and fascia. The water runs behind the gutter, not into the gutter.

To solve this problem, the water retention must be broken. The water has to "Drip" into the gutter.

In order to drip, you need a gap, OR, the shingle needs to extend out far enough to not wick back to the drip edge. Shingles need to stick past the drip edge at least 3/4" min. 1" is better.

Drip edge is ONLY manufactured at a 90 degree angle. Because of this, the bottom of the drip edge touches the fascia. So, the water wicks around to the fascia, and behind the gutter. You can adjust (bend) the bottom edge of the drip edge vertical. This will give you a gap for water to drip, and go into the gutter. That being said, we've recently run into some drip edge with a little bead at the bottom edge. Even gapped, the water whips around that bead, and gets tossed over to the fascia, and behind the gutter it goes.

There is a steel drip edge used on Bardon Homes which has an indent on the under side. This indent is supposed to break the water retention. Whether it works, or not, I don't know. We don't adjust steel drip edge.

Some of the builders are now extending the roof sheeting 1" - 1-1/4" over the fascia. This will create a gap for dripping. Re-roofs have a drip edge, over a drip edge. This creates a gap for water to drip.

It's all about making water go into the gutters. Of course, the gutters also need to be installed correctly in order to properly function...............