Please post questions about anything having to do with roofing

[Frank Albert]

Originally Posted by kshepard

Do you have any theories about the source of the leakage?

I should have mentioned that I sometimes find the butt-joint leaks on dimensional shingles on 12/12 pitches too. The only common denominator there has been that there was a joint below where a dorma or other valley emptied onto the roof.
I now make sure no joints are in that area.

[Frank Albert]

BTW. Why do roofs get a 'Pass' when the starter course is a shingle that has been turned around instead of a shingle that had the tabs cut off and the sealer strip right on the bottom edge? Properly applied like that, and nailed all along that bottom edge, there is no way for the wind to damage the shingles.

[Carl A. Brown]

Thanks Frank.

Good thread Kenton.

[Marcel R. Cyr]

Originally Posted by Frank Albert

BTW. Why do roofs get a 'Pass' when the starter course is a shingle that has been turned around instead of a shingle that had the tabs cut off and the sealer strip right on the bottom edge? Properly applied like that, and nailed all along that bottom edge, there is no way for the wind to damage the shingles.

To answer that question we need to go back here on this page; Architectural Graphic Standards
Copy right of 1970 Sixth Edition.




Now we can judge as to why methods are changing. Look at the weights of the material. Self-sealing tabs were not available in all brands.

Observe where the drip edge is, and the weight of the underlayment. Ice and water shield wasn't out yet.

Now explain to me why we have problems today without an ice and watershield underlayment.?

Explain why roofing today listed as 30 year will have seen it's better days in about 16-20 years opposed to shingles that I replaced on my own house that were 32 years old and still not leaking.

Food for thought.

Marcel

[Kenton H. Shepard, CMI]

Originally Posted by Frank Albert

BTW. Why do roofs get a 'Pass' when the starter course is a shingle that has been turned around instead of a shingle that had the tabs cut off and the sealer strip right on the bottom edge? Properly applied like that, and nailed all along that bottom edge, there is no way for the wind to damage the shingles.

They shouldn't. It's common for the starter strip to be cut from shingles as opposed to using commercial starter strip, but that starter strip shouldn't measure more than 7"-8" wide. A full shingle as a starter strip is a defective installation.

[Kenton H. Shepard, CMI]

Originally Posted by clawrenson

I am considering re-roofing my home within the next year. It is currently a tar and gravel roof - reasonably flat with 2 roof drains and a scupper.

The tar and garvel roof is installed on an rigid insulation that is mechanically fastened to 5/8" t&g plywood roof sheathing. I was thinking about going to a single ply rubber self-adhesive system.

What are the comments - pros and cons regarding such a system?

Claude, I'm still trying to get through the asphalt shingle portion of this. I have seen some strident opinions on this and will do my best to address it which I reach the flat roof portion. If Frank or any other experienced roofers would like to jump in here, feel free!

[Kenton H. Shepard, CMI]

Originally Posted by Frank Albert

Some appear to be a cause and effect of the self-sealing capabilities of the shingles. I've been in long discussions with other roofers. We 'believe' it's partially because water DOES wick under the shinlges at all joints/butts. Because of the shingles seal down capability, the water cannot run out from under the shingle. ( This is also why I fail any roof that used EG nails. They rot off in 6-8 years leaving holes.) The water works itself sideways until it finds relief in the form of a butt joint. It gets under the roof there. It will blister the roof and just flat find opening to leak into the home.

There are two fastening forces to understand.
1.The adhesive strips fasten the shingles to each other. These bonds are weaker with organic shingles, which may be an advantage when shingles need to expand and contract at a different rate than the plywood or OSB roof sheathing.

2.The fasteners (hopefully roofing nails rather than staples) fasten the shingles to the sheathing. The fasteners have certain corrosion-resistant properties depending on how they're made. Frank fails any shingles fastened with electro-galvanized coatings (the most common coating for roofing nails). Hot-dipped coated nails are better.

If you look at the adhesive strip of different brands of shingles, you'll see that some are a very solid strips and some are not so solid.

In preventing uplift (wind blow-off) this is not so important. What's important is that the wind not be able to break the tabs free to flap inthe wind, crease and break.

If you're depending on the adhesive strip to prevent moisture intrusion of the shingles from wind-driven rain, or considering that the adhesive strip may prevent moisture originating from the home interior beneath the shingles from drying to the outside, then the adhesive strip takes ona different purpose. I don't think the adhesive strip was designed as a moisture barrier, but to prevent uplift/wind blow-off.

If you assume that the adhesive strip cannot keep out wind-driven rain (which it won't, in every roof), then you have to assume that moisture will find its way past laps and through joints if the wind blows hard enough from the right direction.

In other words- Asphalt roofs are going to leak if the wind blows hard enough and there's enough rain. Yes, it depends on the design and maybe the installation. Some designs will leak easier than others.

The problem is.. there aren't always easy answers.

[Kenton H. Shepard, CMI]

Originally Posted by mcyr

To answer that question we need to go back here on this page; Architectural Graphic Standards
Copy right of 1970 Sixth Edition.




Now we can judge as to why methods are changing. Look at the weights of the material. Self-sealing tabs were not available in all brands.

Observe where the drip edge is, and the weight of the underlayment. Ice and water shield wasn't out yet.

Now explain to me why we have problems today without an ice and watershield underlayment.?

Explain why roofing today listed as 30 year will have seen it's better days in about 16-20 years opposed to shingles that I replaced on my own house that were 32 years old and still not leaking.

Food for thought.

Marcel

Marcel, we have the same edition, I'll be danged.

[Kenton H. Shepard, CMI]

Originally Posted by mcyr

To answer that question we need to go back here on this page; Architectural Graphic Standards
Copy right of 1970 Sixth Edition.




Now we can judge as to why methods are changing. Look at the weights of the material. Self-sealing tabs were not available in all brands.

Observe where the drip edge is, and the weight of the underlayment. Ice and water shield wasn't out yet.

Now explain to me why we have problems today without an ice and watershield underlayment.?

Explain why roofing today listed as 30 year will have seen it's better days in about 16-20 years opposed to shingles that I replaced on my own house that were 32 years old and still not leaking.

Food for thought.

Marcel

Actually Marcel, you would do us all a great favor if you would answer your own questions in your own words, please.

[Kenton H. Shepard, CMI]

Originally Posted by Frank Albert

I should have mentioned that I sometimes find the butt-joint leaks on dimensional shingles on 12/12 pitches too. The only common denominator there has been that there was a joint below where a dorma or other valley emptied onto the roof.
I now make sure no joints are in that area.

Again Frank, lots of us have not been roofers. I don't understand what you're describing. Are you making a point about butt joints in asphalt shingles in steep slope situations? Are you recommending avoiding any joints below valleys?

[Steven Woods]

What causes these diagonal patterns with asphalt shingles?

[Larry D. Kage]

Originally Posted by swoods

What causes these diagonal patterns with asphalt shingles?

Tha method of installation:

[jkogel]

Some roofers call that a "racked" pattern. It's about speeding up the installation, so watch for other cost cutting measures (or lack of measures ).

John Kogel
www.allsafehome.ca

Kenton, I think he means no butt joints under the spot where water will splash from the eavestrough above.

[Frank Albert]

Yes. If there is a joint, even on a dimensional shingle roof, below a valley, there is likely to be a leak. The 2" headlap will allow water in.

[Frank Albert]

I seldom do flat roofs anymore. And the fire hazard with APP is real.

I lean towards pitching the roof at least 1" per foot. I'm a firm believer in shedding the water.

I don't want to comment on what to use for the flat roof because I don't feel qualified to give a good answer. Other than 'Slope it some' with a rebuild or tapered insulation.
I do prefer EPDM. Loose laid, mechanically fastened on larger roofs, fully adhered on smaller ones.