Alluminum and Slate Longevity

As some of you already know, copper goes south in a hurry under some slate roofs due to acid rain. And within a couple of years if used with EPDM. I have a slate roof that all the steps and other flashing went south within 30 years, maybe less time. Anybody have any real world, east coast data on aluminum flashing on a slate roof? :unsure:

I would go with what builderr said about the copper expanding and contracting in the valley, the clue is usually any cracks or splits can be followed back to where the nail went into the copper.

Another thing you might look for is aluminum be it sheet, nails or clips to hold slipped slates, aluminum and copper are not the best of friends.

anything7pob

Lead as we know it is considered an environmental hazard in some States, they do use a lead coated copper, it would do away with the forgiveness we are used to with the lead we use.

Frank,

Acid rain usually has a negative effect on the slates at worst making them softer and they tend to delaminate, often not to the point where you can't re-use them but very noticeable.

I do sometimes, but SOP is copper or aluminum.

Do you not use lead over there?

That is all we use in England and I`ve never pulled out any soakers that were perished like the ones that you have shown.

Aluminium and copper yes I`ve seen perished flashings and soakers on tiled roofs, lead, never and I`ve stripped hundreds of slate roofs that are over 100 years old (100% of them have had lead flashings).

(The nails are usually at fault, after 100 years the heads start to pop off and the slates slip out, you can also pull up the battens in full lengths with your hands which is nice! but the slates and lead would probably do another 100 years.)

Maybe the rain is not acidic over here, I am not sure.

having worked on numerous churches and older historical buildings around Boston, for the company that did the original install back in the 1890-1910 periods, and being fully aware of expansion of copper in very delicate flashing applications, i can only imagine how much oil canning the valley shown above had gone thru to finally open up like that. Copper valleys under slate roofs generally are never secured to the sheathing but installed with nailing clips allowing it to move all that it wants. Once one wrong fastener is used to secure a repair, all hell breaks loose. Open up a can or Karnak and slather that bad boy up...it's jackleg time.

http://now.msn.com/york-minster-cathedral-will-be-covered-in-olive-oil-to-stop-acid-rain-damage

Here's a coating none of us have done before, I would imagine. A little coat for the flashings, and maybe some for the applicator to shine a bit. :laugh:

That's just where the last drips congregate. The water covers the whole surface, but it doesn't drip as much in the middle of a flat slate. Or just maybe, since most seem to turn down a touch on the sides, the water just drifts that way. Even then, some caulk is probably up above there somewhere. Not always, but most of the time.

Most caulks have acid, not sure what type, in them to enable the curing process. A "non acid curing" caulk needs to be used with copper. I've often noticed streaks on valley flashings directly under the joints in the slates. Why would it concentrate there?

I haven't sl8r. But I have noticed that ridge and flshing caulks are causing problems. I caught on one day when trying to figure why a lot of copper ws burning in small areas. Up the roof from each area would be a small dab of caulk. Certain brands are even labeled "Will harm copper", or the like. And never put it below EPDM. It only lasts 2-4 years.

Tinner, have you noticed a difference in flashing wear with different varieties of slate? I've seen it with Pa slate but not with Vermont. I've gone to lead coated copper for flashing and built in gutters but I don't see why a .032 or .040 alum wouldn't work where soldering isn't needed.

Stocker 5130 Said: Might be worth a shot to try heavy gauge stainless steel. If youre gonna try with aluminum, youre gonna need a minimum of .032, maybe even .040.

The aluminum pipe collars and what appear to be orininal aluminum bibs are all undamaged. No rubber on the collars, of course, but the aluminum was fine. The owner says there may still be a leak up top in an area I repaired a year or so ago. After finding about 20 short slate on this tear off, I may have to go up and inspect every headlap.

Old School Said: Wow, that is tore up What was beneath it? It doesnt make sense that it would just eat away like that for no reason. Are there any large coal burning power plants up wind of you?

VAPWR plant at Dutch Gap is about 30 miles S-SE.Lots of EPA scrubbers at work there and only see steam, no smoke.

Might be worth a shot to try heavy gauge stainless steel. If you're gonna try with aluminum, you're gonna need a minimum of .032, maybe even .040.

Did the owners have someone wash algea/moss of of the upper section with a muratic acid solution? Sulphuric acid is the same, whether it came from a bottle or the sky.

Three roofs dump on this puppy. The copper miked at 27 ga. which would make it 12 oz. copper. They almost act as a valley. It narrows somewhat. I'm covering them with a 3" wide term flashing I'm putting behind the mansard felt. That's help keep leaves from building up 'in' the flashing, and keep direct water flow off the new 20 oz. steps.

I took a few pix. Owner said it starting leaking in it's 25th. year.

http://www.rooferscoffeeshop.com/rcs/users/tinner666/http://www.rooferscoffeeshop.com/rcs/users/tinner666/

I sometimes feel I'm the only roofer that extends my steps 2-3" above slate. Many idiots around here cut them like they would for shingles and then either raise them up to an improper coverage, or lay them in place without nailing. A little of both was done on this roof.

The Job!