Lo Slope Roofs!

In another thread we mentioned the minimum slope for slate would be 6/12. True. (On another forum.) Now, let's talk about real life experiences and observations.

Here, we have many, many examples of historic properties that have slate on slopes of 2/12 or 3/12. Everywhere! There is evidence that felt was used when the roofs were installed back in the late 1800's and early 1900's on these jobs. All were done with a minimum of 15# felt and 2" headlaps. On planks. I've repaired or replaced many of them and now will shed some light on my personal findings. This has nothing to do with rules, books, or spec sheets. Just life.

The vast majority of these lo-slope slate roof are on porches.

One in 2000 might have copper nails. I seldom see that. Primarily because of the nail used, believe it or not. Keep reading.

Quite often I get a repair call and find evidence of one or two leaks. Not water pouring in like you would expect. I find that the nails have rusted into powder and the slates have slid out. If the leak hasn't been going on for years, there is no wood damage and a simple repair is all that's needed. Sometimes, I find the whole roof is sliding off and the owners can't or won't replace it now. They will pay for me to slide all the un-nailed slate back into place. Amazingly, they stay in place for many years without leaking again. In each of these cases, the underlay is a black powdery dust that used to be felt, or just wood.

There is also another factor that really causes most leaks on these porches. They are used like scaffolding by painters, handymen, and the HO's to paint and maintain the homes, or whatever! Some folks around here even set chairs and lounges on the slate to sunbathe! Lots of broken slate and the resultant leaks there!

Real life tells me this. Slate breathes, and you can look under the slate from gable to gable if you want proof. Planks are the best sheathing. Even if they get damp from the lack of headlap, they'll dry out in a hurry and still go 100+ years. Plywood won't. If they get really wet and keep getting wet, they'll rot out in a few years from a single leak. The damage will be confined to the area of the leak too. A single 16" plank may be the total wood repair. Not so with plywood. 1/2 sheet minimum there!

wywoody Said: With tile, because of the thickness of the butts, the surface of the tile is roughly 1/12 less than the roof pitch of the framing. If you shorten the courses, you lessen the pitch of the tile surface even more. Extra lap is one of the worse things you can do when you get under 5/12.

Funny that you should mention this. This roof was a problem child that after much arguing the very same point you just made we stacked it up and did full-coverage ice & water.

It worked fine ~5 years, until the house across the street blew up from a gas leak.

Small pictures don't do it justice. You can see the shock wave in the tile, the other photo shows where the blast stood tiles up, then dropped them.

It picked the entire roof structure up a bit and dropped it. Soffit nails jarred loose and showing 1/3", batts knocked loose and up 1/4". Leaking around the nail holes at a few batts.

Walls are since re-built/re-modeled and they're chomping at the bit to refinish the interior, so we're probably going to end up stacking it all back up and ice&watering it again shortly.

Not that I'm complaining, but we're severely lacking snow here this year. I guess maybe the lack of snowdrifts has me drifting forum threads instead...

Due to a tornado and hail storm, everybody and their brother are shinglers here. Fine with me, they make me a lot of money.

Off her rocker nut-case called (9 times!) for this one. No idea who installed it. She called 3 more times before I was even back to the shop after tarping it to demand to know when we'd do a permanent repair. Boss told her "We're not!"

I know very little hands on about slate roofing . What I know about slate I have learned from craftsman on this site. Thanks B) :) :) B) Deep Down In Florida Where The Sun Shines Damn Near Every Day

You are RIGHT. No dought in my mind.

I especially like the manuf. rec's on I&W around skylights and at ridges and hips.....The I&W is under the felt!....Any moisture that got on the I&W, would run under the felt! amazing!!!! I get the same feeling everytime an Obama sticker shows up on the car in front of me.

Run across many, many, very old, wood shingle & comp shingle roofs under 4/12.....Down to 2/12....sometimes 1/12....NO felt/underlayments. Proper coursing & flashing work does the trick.

I recall, (20 yrs ago +/-), getting into a ridiculous argument with an inspector, as well as a com[petitor, on the subject of shingles installed on near-flat porch/patio roofs....They just couldn't get it through their thick skulls that the UBC's, (at the time), intent was referring to "double coverage" of SHINGLES, NOT underlayment! Dorks!

The majority of homes built at that time in that particular area, were 4/12 with low-slppe porch & patio roofs....We never shingled anything under 4/12....Hot or cold BUR only....My competitor, for years, installed shingles on 1/12 porches w/2-layers of 15# felt with the blessings of the ingnorant bldg. dept. Replacing all those low-slope shingle applications became quite a little market of it's own. Now, had he instaslled w/dbl coverage, (2.5" exposure), as intended, (instead of their knuckle-headed notion of dbl felt), probabaly would have worked.

I believe that mindset, (dbl felt), made it into the UBC &/or IRC later???? Just goes to show ya.....

I should have posted a link to one I did a few years ago. Went up 2-3 sizes to gain headlap and look like it originally did in 1910.

http://www.albertsroofing.com/New%20Slate%20Roof.htm

I agree Tinner. over the years I have seen many non-tradtional situations, probably better called "against mfger standards" and "below code minimums", if properly installed last as long as if it did meet normal. requirements. Actually I've done many myself and I dont recall any call backs. Of course I always informed the HO that this did not meet minimum standards so the was a very limited warranty in this situation. I think with the repore I have with my clients, that if there were a problem they would have called me and I would have fixed it