Design flaws show themselves.

[Darren]

I tell my clients something along these lines:

Discharge from upper sections of gutters should run into the lower gutters via downspout extensions or terminate directly to the ground rather than discharging onto the roofing materials.

[Terence McCann]

I tell my clients something along these lines:

Discharge from upper sections of gutters should run into the lower gutters via downspout extensions or terminate directly to the ground rather than discharging onto the roofing materials.

Me too.

[Chad Fabry]

The manufacturer never intended for the shingles to handle this volume of water, IMHO.

Are you saying that manufacturers don't intend for shingles to be installed in valleys? The quantity of water is no different.

The valley only carries the water from the triangles directly above it- there's no impact considerations either and the water being discharged from a smooth vertical pipe is moving much faster than water running down a sloped irregular surface.

The area below a roof directed downspout may be subjected to many times the volume of water than a valley would be subjected to ie a 20x 40 roof could be discharged at a single point.

At any rate, valleys wear out much faster than the adjacent fields.

[John Kogel]

No,

That's not what I said at all. The oxalic acid secreted by the moss and algae clinging to the shingles is what breaks down the material. The water only washes the loosened material away.

He titled the thread "Design flaws show themselves." I don't think it's a design flaw at all. Nothing really bad will happen from that water as long as they are careful to remove any algae, moss or lichen as soon as it begins to appear, instead of leaving it there to continue to feed and loosen those granules. These examples they are showing all show signs of algae or moss - is it any wonder there is wear there?

ONE TEAM - ONE FIGHT!!!

Mike

OK, so it is only a problem if there is moss and algae on the roof. It is a design flaw for a roof on the wet coast, because the constant supply of water concentrated in that area encourages the growth of moss and algae, along with more than average flushing action.

BTW, I posted pics 2 and 3, of a roof with minimal moss growth on it, but lots of wear. Well, it looks like the slime was removed with a pressure washer, doesn't it? []

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[Jim Katen]

I can't get behind the idea that dormers are a design flaw.

In Brandon's original post, the design flaw is the vent under the upper roof's dripline.

One roof plane discharging onto another isn't a "flaw."

[Marc]

Changing camps and some of my boilerplate (not actual wording):

1) Downspout runoff onto a lower roof surface may accelerate deterioration of the affected shingles if the upper roof surface served by that downspout has Gloeocapsa Magna (usually referred to as algae) growths on it.

2) Remove Gloeocapsa Magna (usually referred to as algae) growths from the roof surfaces to prevent accelerated deterioration of the shingles.

Good thread.

Marc

[Brandon Whitmore]

Mike, perhaps it's just my grouchy self this morning, but it seems like you are coming across as scolding school children for not "getting it". If it has been said before, and you are right, then perhaps the info. wasn't provided in a way that the average pupil could understand or agree with.

He titled the thread "Design flaws show themselves." I don't think it's a design flaw at all. Nothing really bad will happen from that water as long as they are careful to remove any algae, moss or lichen as soon as it begins to appear, instead of leaving it there to continue to feed and loosen those granules. These examples they are showing all show signs of algae or moss - is it any wonder there is wear there?

Perhaps I should re- title my thread: "Under perfect situations, these details should work; otherwise, they may not."

Mike, perhaps it is the oxalic acid causing all of the premature wear. Perhaps there are multiple factors involved. If the only cause is oxalic acid, I would still consider the design an issue. Is oxalic acid being washed down into the gutters, and then being concentrated onto the shingles below? I'll admit I haven't researched all of this stuff, and need to. I'm just talking out loud and getting some discussion going.

as long as they are careful to remove any algae, moss or lichen as soon as it begins to appear,

Can algae be safely removed, or just bleached (ARMA says bleached)? If it is just bleached, then are you really doing anything to protect the shingles?

[hausdok]

Sorry if you feel scolded. That's not my intent. My intent is to make you understand that some of the ideas you are floating around here, such as the idea that the open inner end of that upper gutter emptying onto that sloped roof plane is somehow going to cause massive erosion when it won't/doesn't until one is careless enough to allow a buildup of slime and gives that slime the opportunity to start eating the roof - it's the same with the downspouts.

Here's what I know,

When I find moss or algae growing on masonry and I lift it or scrape it, I invariably find the surface beneath it softer or more worn. Sometimes the mortar directly behind moss is completely trashed while mortar that's clean is hard and healthy. With mortar, I think that has something to do with the fungi eating the lime; I don't know what the hell it's eating in the concrete and red brick.

When I find downspouts from upper roof discharging onto lower roofs on the sunny sides of a house where the UV prevents growth of moss or algae directly beneath the downspout discharge point, the roofs are fine and don't show any accelerated granule loss over the rest of the field. However, on the same house when I go around to the east and north sides where the sun can't reach those areas, and if there is moss or algae below those discharge points, there is almost always accelerated granule loss below the spouts, whereas when a homeowner has been diligent about removing the moss or algae and has done it with chemicals and low pressure water and not a pressure washer, there is no appreciable difference in the surface texture or flexibility of the shingles.

When I find algae ignored on flatwork the flatwork will have more wear there. The surface will be just a little bit rougher - as if it's been slightly sandblasted.

When I find moss on roofs, whether wood or asphalt, there is always a cost in wear. Shakes will be punky from the affects of the acid breaking down the shake into food - the granules on an asphalt roof will slough off more easily where there's been moss growth or the roof is algae stained - just rub your palm over the surface in areas with moss and algae on them versus clear areas where the sun hits the roof and prevents moss growth, there is a difference. I believe that there is some kind of a chemical process that takes place when the asphalt in the shingles is left with fungi on it for too long.

When horses asses with teeth have climbed up onto roofs and pressure washed them I can always tell where the moss or algae stains had been because the amount of erosion of protective granules on the areas where there had been moss or algae is many times what it is where the rest of the roof was otherwise healthy. I'm not talking about the kind of erosion you see where they shove the wand right up against the shingle - I'm talking about an overall lessening of granule concentration that can make those areas look like they are 40 year old shingles on a 12 year old roof that's been cleaned. If there is no detrimental effects from the moss or algae, why isn't the accelerated wear consistent over the entire roof that's been pressure-washed?

I used to think that it was simply because the pressure-washing guy got his wand too close and because he or she would have concentrated more on the area with moss. I thought that until a friend of mine, who is a total incompetent when it comes to doing anything around his house, asked me if I would teach him how to properly clean his roof. One slope of his 4 year old architectural-grade asphalt roof had a pretty good moss growth on it; another slope had some really dark ugly algae stains that he referred to as "dirt."

I got up on that roof with an ordinary garden hose and rinsed most of the moss clumps off easily without much pressure. Then I got down to examine the surface and found that where there had been moss clumps the surface texture was far rougher - sort of like the difference one sees between 40 grit sandpaper and 180 grit sandpaper - very significant. Then I examined the moss clumps that I'd washed into the gutter and found the bottom of them with granules embedded in the moss - when the moss was removed the granules came with it - and this without any pressure washing or use of chemicals.

Then I mixed up a solution of sodium hypochloride mixed with a little bit of liquid detergent to use as a binder and hit that roof. I'd picked an overcast day to do this so that the water wouldn't evaporate quickly and the stuff would work the best. I saturated that roof, only in the areas that needed cleaning, allowed the solution to work for a few hours and then rinsed the roof off with that garden hose using a soft spray. It cleaned right up but when one looked carefully, one was able to see that where the moss clumps or algae stains had been there was a subtle worsening of granule erosion over those parts of the same slope where there hadn't been any fungi. That made me a true believer; if I hadn't seen it for myself, I would have forever thought that the pressure-washer guys were causing all of the erosion instead of only part of it.

Here's another thing I've noticed; asphalt shingles left with algae stains on them for an extended period of time are noticeably more brittle than those without the algae in areas where the fungi doesn't grow. I've corner tested shingles on a 10-year old high-quality asphalt roof in the middle of long dark algae streaks and found them with the flexibility that I'd normally expect with 20 years of weathering, whereas the shingles on the same roof that are in areas where there is no algae or moss the lamina is still very pliable and consistent with what I'd expect from a 10 year old roof.

I don't say this because I think I'm smarter than anyone else here; in fact, I think I'm a whole lot dumber than most of you here - you guys are downright scary - and I don't have a study done by accredited scientists that I wave around and say, "See, I'm right." I only have nearly 15 years of very careful observation of roofing materials while climbing around on roofs in this damp fungi-rich environment to my credit.

I didn't dream this stuff up on my own; it was somewhere in the late 90's when I read an article somewhere written by some building expert - Old House Journal perhaps - where that expert mentioned the detrimental effects that oxalic acid has on various materials and he mentioned moss and algae (fungi) as one source of that acid. That made me curious and after that I began really paying attention to where moss and algae were growing, ages of roof covers, materials, etc. and how the fungi was affecting them. I'm convinced that I've got it right though I know most of you think I'm loopy.

By the way, this doesn't only occur with moss or algae; tannic acid leeching onto a roof from tree debris left on the roof also seems to cause an almost identical effect. I've looked at hundreds of roofs where wet tree debris has been ignored for months on end and when I've pulled a soaking wet mat of moldering leaves off those valleys found significant granule loss under those areas where the debris had accumulated, whereas other areas of the same valley without debris were fine. I've seen roofs where annual leaf fall onto the surface has worn out only those sections of roof where the leaves accumulate and the rest of the cover is still fine. Some debris from some types of trees seems to be more aggressive than from others.

I don't think it's just coincidence - after all, if tannic acid can soften dry hard leather and change its composition such that it remains always pliable after that, there has to be something to it.

Anyway, think about some of the things that you've been saying. Downspouts discharging onto lower roofs will cause...etc. and ask yourself why it doesn't happen with every single roof where they are configured like that - because it really doesn't - and ask yourself if those are fair and credible statements or are imagined issues based on an entirely different and misunderstood mechanism.

ONE TEAM - ONE FIGHT!!!

Mike

[Bill Kibbel]

Mike,

In the above post, when you refer to "algae", your not talking about the black streaks (gloeocapsa magma) are you?

Gloeocapsa magma is not an algae, doesn't produce or excrete oxalic acid and doesn't damage shingles.

[Terence McCann]

You can't get any clearer evidence than Darren's picture. The fact is indisputable.

Now, if the excess water caused excessive growth of moss, lichen, algae which destroyed the shingles in that area so be it. Whatever the case it is a good idea to inform the client to extend downspouts to the lower gutter.

I still think it's bad form to expel a lot of run off on a small area of shingles (a little Dormer notwithstanding) but God forbid we tamper with the aesthetics of the 2,200 sq ft McMansion. What will the neighbors say Harry?

[Bain]

You can't get any clearer evidence than Darren's picture. The fact is indisputable.

Now, if the excess water caused excessive growth of moss, lichen, algae which destroyed the shingles in that area so be it. Whatever the case it is a good idea to inform the client to extend downspouts to the lower gutter.

I still think it's bad form to expel a lot of run off on a small area of shingles (a little Dormer notwithstanding) but God forbid we tamper with the aesthetics of the 2,200 sq ft McMansion. What will the neighbors say Harry?

Water causes erosion. The Grand Canyon is all the proof one needs of that, though Darren's photo makes a pretty good case, as well. But the solution in Darren's photo is to extend the leader along the tops of the shingles so it empties into a lower gutter. That would be ugly. It would trap leaves. And the lower gutter might be overwhelmed and allow water to flow back into the soffit.

I think this is one of those things that, while not ideal, is just the way it's gotta be.

[hausdok]

Hi Bill,

I'm talking about both the green algae slime and the dark streaks. I don't know squat about geowatsis except for what's been posted here. I don't know if the black stuff streaking roofs is the same thing or a different variety of fungi. I've been told that unless one is a macro biologist, one can't tell one from the other anyway.

What I know from personal observation is that the black stuff that streaks roofs out here that I'm calling algae does cause wear on the roof exactly as I've described above.

As for the "water causes erosion" comments above, I don't dispute that water causes erosion and that there is always some erosion of those protective granules due to rain. What I know from careful observation here is that when there is no whatever it is growing under the discharge points of gutters there is no appreciable difference in the wear on the surface of a roof between the area below where one of those spouts discharges and the rest of the field of the roof during the normal lifespan of a cover. I will concede, and I should have said this above, that when a roof is beyond the end of it's expected service life and crystallized all the way through the lamina and the granules are sloughing off easily that there is significantly more wear directly under spouts; but I haven't seen that with roofs in their normal service life when those spouts are where there is sunlight and nothing growing on the roof and where no jackass with a pressure washer stressed the surface.

ONE TEAM - ONE FIGHT!!!

Mike

[Brandon Whitmore]

Thanks Mike,

Post #33 of yours makes a lot of sense and has got me to thinking. I'm pretty sure I was at least partially mistaken as to the cause of the premature wear. I'll pay more attention to the roofs I inspect in the future, and see what I can figure out.

[Bain]

Hi Bill,

I'm talking about both the green algae slime and the dark streaks. I don't know squat about geowatsis except for what's been posted here. I don't know if the black stuff streaking roofs is the same thing or a different variety of fungi. I've been told that unless one is a macro biologist, one can't tell one from the other anyway.

What I know from personal observation is that the black stuff that streaks roofs out here that I'm calling algae does cause wear on the roof exactly as I've described above.

As for the "water causes erosion" comments above, I don't dispute that water causes erosion and that there is always some erosion of those protective granules due to rain. What I know from careful observation here is that when there is no whatever it is growing under the discharge points of gutters there is no appreciable difference in the wear on the surface of a roof between the area below where one of those spouts discharges and the rest of the field of the roof during the normal lifespan of a cover. I will concede, and I should have said this above, that when a roof is beyond the end of it's expected service life and crystallized all the way through the lamina and the granules are sloughing off easily that there is significantly more wear directly under spouts; but I haven't seen that with roofs in their normal service life when those spouts are where there is sunlight and nothing growing on the roof and where no jackass with a pressure washer stressed the surface.

ONE TEAM - ONE FIGHT!!!

Mike

You know I likes you, but you're being stubborn on this one. There are lots of variables that would have to be taken under consideration, like the higher roof's area and slope, but there's no denying that running water deteriorates and damages things.

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[Terence McCann]

What are we looking at John?

[Bain]

What are we looking at John?

A gutter downspout/leader that's missing its extension. The water flowing down the foundation wall destroyed the mortar joints.

Like I said previously, lots of houses in my area have gutter systems similar to the one in Brandon's photo, and I don't think there's much that can be done about them without gunking up a house's appearance. But to say that one shingle that has significantly more water trailing down it will last as long as a shingle under normal circumstances simply isn't logical.

[Terence McCann]

I have never, in my life, seen 6" duct used as a downspout. The red thing next to it looks like a built in bookshelf.

[Bain]

I have never, in my life, seen 6" duct used as a downspout. The red thing next to it looks like a built in bookshelf.

The photo was taken at a 10K square foot commercial building that was really tall, and which had box gutters that were junk. The bookshelf is actually a boarded-over basement window with bars in front of it.

[mthomas1]

In just show clients this, and let them make up their own minds about whether poorly controlled runoff can erode roofs.

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[hausdok]

In just show clients this, and let them make up their own minds about whether poorly controlled runoff can erode roofs.

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Except one can clearly see that 3-tab is completely shot. So using that picture to try and prove erosion of a roof's surface is like using a mummy to show a flawed complexion.

One asphalt roofs are toast - and that one is - they erode like crazy regardless. An interesting thing to note though; see where the copper gutter discharges onto that roof? Look at how good the shingles look at that small spot. In this case, the copper kept organisms at bay and instead of being the worst condition those shingles are the best.

ONE TEAM - ONE FIGHT!!!

Mike

[Richard Moore]

Water causes erosion. The Grand Canyon is all the proof one needs of that...

Not so fast there.

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It's not so much the water as the abrasive silt it carries with it. With the Grand Canyon, as with most rivers, an almost endless supply of silt is carried to it from the banks of stream feeders, etc, especially after heavy rains. And then, as that "slurry" wears away at the rocks those particles are also added to the abrasive mix. If it was just water, then I wouldn't expect PVC piping to last very long.

Once the initial loose granules come off (and most of those remain in the gutters) there really isn't that much abrasive material in the water off of a roof. Some maybe in a dusty area, but not that much. Like someone else above, I suspect the damage in Darren's photo is a mostly a mix of overzealous cleaning and, maybe, foot traffic.

Same thing. BTW, with those neat arches in Utah. It's wind driven sand, not the air itself, that caused 99.99% of the sculpting.

I'm not saying it's the best design in the world, but I don't get exited about it (or report it) unless a downspout is aiming discharge across the shingles...like today's.

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[Phillip]

I have seen where the shingles have been worn from the water from a downspout.

But with Mike little talk I trying to remember if the homes that had this problem had a lot of shade and some type of growth on it.

I know I will be looking a little harder at this when I see it again.

[Erby]

I'm so much smarter for participating here!

[Chad Fabry]

Water causes erosion. The Grand Canyon is all the proof one needs of that...

Not so fast there.

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It's not so much the water as the abrasive silt it carries with it. With the Grand Canyon, as with most rivers, an almost endless supply of silt is carried to it from the banks of stream feeders, etc, especially after heavy rains. And then, as that "slurry" wears away at the rocks those particles are also added to the abrasive mix. If it was just water, then I wouldn't expect PVC piping to last very long.

Once the initial loose granules come off (and most of those remain in the gutters) there really isn't that much abrasive material in the water off of a roof. Some maybe in a dusty area, but not that much. Like someone else above, I suspect the damage in Darren's photo is a mostly a mix of overzealous cleaning and, maybe, foot traffic.

Same thing. BTW, with those neat arches in Utah. It's wind driven sand, not the air itself, that caused 99.99% of the sculpting.

I'm not saying it's the best design in the world, but I don't get exited about it (or report it) unless a downspout is aiming discharge across the shingles...like today's.

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Water is pretty erosive on it's own. That's why we de-burr copper tubing and do everything we can to prevent turbulence in the tube.

It's why we don't pressure wash roofs- velocity and volume directly correspond to erosion. The water from my barn roof drips to my concrete parking area and after ten short years I can see a definite area of wear.

Impact from rain and concentrated flows from upper planes move the surface of the shingle downhill.

[Garet]

Mike's dissertation on biology makes a lot of sense to me. I've heard people making an issue of this for years, and yet I've only see worn shingles below a downspout once or twice in 10 years at this gig. In my dry climate I also rarely see things growing on roofs. Sounds like another case where regional differences abound in the way building perform.

Great discussion.