Shingles

[Don]

Why do shingles have 2 vertical slots creating the 3 tabs?

[Pierre Levesque, AIA]

So that they can look like old wood or slate shingles in size and shape. At some point during the asphalt technical revolution, someone made a machine that could produce 30 inch wide sheets of asphaltic bitumen... then they were divided sliced like cheese and divided equally into 3 tabs so as to resemble classic shingles. I think an even better question might be "how come shingles aren't manufactured in standard 4 foot sections using 4 tabs?" Technical limitations of the product, invented before the 4 foot measurement became standard, or a combination of both?

[Don]

During Charley millions of tabs were snatched off of thousands of roofs. I believe the vertical slots cause weakness in the shingle. And....the typical nailing pattern is to place the nails directly above the top of the slot, about 1" away. It seems to be a procedure that is doomed to fail, especially if the nailor uses staples, that act like little knives, instead of roofing nails. Its generally assumed around here that if the shingles are installed in the summer, after 30 days they are *sealed*, the backing adhesive has bonded with the shingles below. However, hurricane season doesn't end until the beginning of Dec. and if shingles are installed in Nov and it happens to be cloudy or cold then the shingles could be susceptible to a failure in the event of a late season Cat 1 or 2 storm.

(My cousin counted over 700 tabs missing from his 15 y.o. shingle roof. He got the whole thing removed and new shingles installed and made money on the deal. The insurer paid him $13k for it and he paid the roofer $9k. He's one of the rare people that benefitted from Charley.)

[gruhn]

That's about the lifetime for generic shingles, no?

[Daniel]

All the US shingle manufacturers I know are giving a 20-year warranty on their basic generic shingles. It should mean a properly installed shingle roof should last at least 25 years. Then, read Don reservations and make up your mind.......

You want a real long lasting good shingle roof? Lay it over a minimum 16-18 mm thick exterior grade plywood deck (REAL exterior grade). Cover the deck with a strong underlayment felt. Use European Standards shingles, NOT ASTM. Give preference to APP-modified bitumen shingles, not the standard oxydised bitumen ones. Make sure of proper ventilation. Nail it, do not stapple it. You got it. Not cheap, but you got it. Cheers Daniel

[gruhn]

So, "no" it is again. Sigh.

[gruhn]

Seems likely. Nothing lasts in AZ. There is no such thing here as "glue". Of any sort. We use velcro for everything ;-). I'd expect distance between extremes of temperature to play and even humidity. Not sure diet of occupants comes noticably in to play.

[Daniel]

If the roof assembly is properly ventilated, climatic conditions do not really modify the shingles life expectancy (Beside heavy hurricanes, for sure). Don't forget, it is small elements, so they don't suffer from temperature, moisture, etc, as a monolithic membrane or similar.

I am doing shingles in tropical/equatorial countries since quite a while, no specific problems beside the fungus attack risk, but we know how to tackle that. Colours don't really change the life expectancy. A light colour will reflect more heat but will be more prone to colour fading, darkening than a darker colour, that's all.

I am talking, obviously, about good quality US or Canadian shingles, not about..... mmhhh! I won't name "them" here, thay may sue me :-) Cheers Daniel