DIY Home Improvement, Remodeling & Repair Forum > DIY Home Improvement > Roofing and Siding > metal valley..appropriate or risky on 3/12 pitch?




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Old 08-09-2009, 09:16 PM  
bill's quest
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Default metal valley..appropriate or risky on 3/12 pitch?

I expect to be meeting with the "supervisor" of the roofing job, and I would find it helpful to judge an earlier comment by him. As some may know...(i've posted enough lately) my roof is three over twelve. The supervisor talked me out of my request for metal valleys. I wanted them because on the last installation I saw a lot of organic debris gather in the valley and how easily it worked its way under the shingles. Even though this would be an add on to the job which I was willing to pay the supervisor insisted that valleys on a low pitch roof was a bad idea....despite that there was going to be ice and water shield underneath it. He said that he felt certain that within three years I would have a leak because of water working its way underneath the shingles and that I would have water dripping through my windows. Maybe I heard him wrong...but I gave in thinking that maybe his crew did not have the expertise in metal valleys and that I should not force this. I was under the impression that metal vallyes are fine if they are done right. Another possibility is that he did not have the correct metal on hand (which was true) and that this would upset his schedule.

Was the supervisor's position to reasonable? If not, I feel more careful to question his creditability in the future.



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Old 08-10-2009, 07:53 AM  
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Metal valley's are always better than any others "if " they are installed correctly.This is for the northeast.
They need a bend at the edges and in the center so the water will not wash up the other side in heavy rains or Ice backups. Google metal valley.
Ice and water is the best thing for a roof since sliced bread. So even if water did get under the metal while freeze ups occur or heavy rain, it will not get past the Ice and water shield.
I recommend copper as the other metals will deteriorate quicker.

Always read up on as much material you can before getting any work done, or hire another professional to keep them honest and look at thier work.



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Old 08-10-2009, 09:10 AM  
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fwiw..i did a lot of the homework on the internet...and knew many of the features for how a metal should be done...but I admit they wore me out on their resistance at the very last minute when the roof was scheduled and i neglected this resource...but it is still not too late for negotiations..I have not paid them


just to be sure....in the real world...as this contractor would say...how sure are you that a metal valley is appropriate for a low pitch roof....?

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Old 08-10-2009, 09:44 AM  
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Have you looked here?

http://www.metalroofing.com/v2/forums/index.cfm

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Old 08-10-2009, 11:20 AM  
bill's quest
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craigfl,

Not a good sign, could not register to log in...many many attempts....i assume that there is not a post there already dealing with my question....and that I would have to initiate the question

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Old 08-10-2009, 03:01 PM  
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Try the new link...

Sorry for the bad one.

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Old 08-10-2009, 06:59 PM  
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CraigFL:

The poster is concerned about how the valleys of his roof are done. He wants galvanized metal bent to fit the valleys of his roof before the shingles are put on. Your link is to a web site about metal roofing. That would include roofs that have metal shingles and "copper roofs" that are typically only installed on the most expensive of homes.

Bill's Quest:

I'm no expert on roofing, but I did act as the "general contractor" when my sister's house needed new shingles. (Basically, the family relied on me to make all the decisions on what to do, and the Bank of Dad paid for it.) That's because it's not really possible to hang around DIY Q&A forums for years and not learn a little bit about everything, including shingle roofs. I haven't responded because I was hoping a roofer would be answering your questions, and a roofing contractor would know vastly more than I.

I think you may be forming an opinion on metal flashing based on insufficient or incorrect information. Where I live, roofing contractors don't use galvanized metal in the valleys hardly at all anymore.

Standard practice years ago was to cover the valley with tar paper, nail your galvanized metal down and shingle up to the valley from both sides, typically leaving a 2 inch gap or so between the shingles. The problem with this system is that if leaves and stuff accumulate in the valley, the compost that forms up there can plug up the valley so that water ends up flowing laterally sideways under the shingles. You have to remember that the galvanized metal is typically only 16 inches wide, and water will flow laterally 8 inches under the shingles. And if the water sits on the tar paper too long, it can start to leak through it.

The other problem with the galvanized valley is that if water gets between the shingles and the galvanized metal, and subsequently freezes, it's going to expand. Since the roof is covered by tarpaper when you shingle, and most roofers use pneumatic nailers, they can neither see what they're nailing into, nor can they get any "feel" from the pneumatic nailer that the nail is driven solidly home like you can from a hammer. So, if it just so happens that they put a nail right into an old nail hole, they have no way of knowing that they've just created a potential roof leak.

If water gets under the shingles there, and expands, it's going to push the shingle up and pull the nail outward a tad. That nail hole will then leak water if water gets under that shingle again.

Nowadays, what they do is put ice and water shield down in the valley first. (I don't know if they put tar paper over the ice and water shield or not, but it's irrelevent to the discussion.) That ice and water shield is a sticky bitumen strip 36 or 42 inches wide, so it extends a lot further from the valley than galvanized metal would. So, the liklihood of water spreading out under the shingles as far as the tar paper is very much less.

Also, the bitumen is a soft material and on a hot day it becomse a very viscous liquid and flows around things like nails to seal off nail holes from leaking water. So, if the same thing happens, the bitumen ice and water shield will seal up around that nail on the next swelteringly hot day to plug that leaking hole.

Basically, if your roofer installed your roof the way it's being done in Winnipeg now, your roof valleys are more waterproof than they would be with galvanized metal in them.

My feeling is that your roofer simply didn't understand why using ice and water shield made for a more waterproof valley than galvanized metal, but was aware that it did. He certainly didn't want to say: "Yeah, but then there's a much better chance your roof will leak." cuz then you'd be losing sleep. But, he was probably aware that they way they're doing it now is better, but didn't understand why.

PS:

Quote:
but I admit they wore me out on their resistance at the very last minute when the roof was scheduled and i neglected this resource...but it is still not too late for negotiations..I have not paid them
Don't go there. You need to know about something called a "builder's lien". If someone does work on your house, and doesn't get paid in full afterward, they can put a lien against your house. That means that if you ever sell your house, the buyer's lawyer will check to see if there are any liens against the house. If so, then the person holding the lien is legally entitled to get paid before you get what's left of the purchase price. So, refusing to pay or haggling with your contractor over price is not a great idea. If you both dig in your heels, and you end up with a lien on your house, then he's gonna get paid eventually anyhow. And, there could be interest accruing on that lien, so it could end up costing you a lot more than it will to pay up now.

Whenever I have a tenant moving out on me because they've bought a house, the chances double that they're gonna skip out on me without paying the last month's rent and not lift a finger to clean before leaving. They think that once they're in their own house, I can't do squat. It's only when they find out I've put a lien on their house that's accumulating interest that they realize I have them over a barrel. Every experienced contractor worth his salt will know his way around the law courts building in your town just like every experienced landlord will.
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Old 08-10-2009, 07:56 PM  
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Bill, Nestor and InspectorD have hit most of the points on a metal valley. In my opinion either a closed valley or a metal valley will be a functional option IF installed correctly. Either one can fail if not properly installed. Metal valleys should NEVER, I mean NEVER be nailed directly into the valley material. When we form a valley pan "W" we turn the outside edge back onto itself and use a clip to secure the edge. Galvanized is not a suitable material option for valleys, at a minimum a painted galvalume with a Kynar finish and a 3" head lap.

Closed valleys with ice and water will last the life of your shingle. The big things about valleys are what we call "tipping" the valley shingles. This means cutting the point of the shingle under the coarse that is visible. This stops water and debris from catching the top edge and running across the course, damming debris and causing a potential leak. This should be done on shingles and in a metal valley.

When metal valleys are installed in a shingle roof you have a material that will generate a lot of heat, I have seen ice and water become runny and ooze at the fascia. There is a similar product made by Tamko "Metal and Tile" underlayment that will withstand the heat generated by metal valleys. Certainteed also make a high temp SA underlayment.

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Old 08-11-2009, 12:54 AM  
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Olddog/Newtrick:

You seem to be very knowledgeable about roofing, so I was hoping you could explain some things in your post:

1.

Quote:
Metal valleys should NEVER, I mean NEVER be nailed directly into the valley material. When we form a valley pan "W" we turn the outside edge back onto itself and use a clip to secure the edge.
Is this done to accomodate thermal expansion of the metal valley. That is, the "U" shaped edge of the metal valley can slide up and down inside that clip. Do the clips stick up much so that stepping on a clip would damage the shingle? I worked out that for a -40 deg. C to +40 deg. C temperature change from summer to winter, you can expect to see a change in length of 3/16ths of an inch in a 15 foot long valley.

2.
Quote:
Galvanized is not a suitable material option for valleys, at a minimum a painted galvalume with a Kynar finish and a 3" head lap.
This was the first time I've heard of "galvalume" and Kynar, so I googled them to find out what they were:

http://www.mcelroymetal.com/elements...M620option.pdf
Galvalume is similar to galvanized sheet metal, except that instead of having a pure zinc coating on both sides of the steel, galvalume has a coating that's about 55% aluminum, 43.5 percent zinc and 1.5 percent silicone. Apparantly, this alloy is more durable than pure zinc on steel, so galvalume coatings protect the steel much longer than the zinc coatings on galvanized steel.

Kynar 500 paint
Kynar Homepage
Kynar 500 is a high end paint that's used on metals to protect the surface of the metal to exposure to the elements. It uses a binder that's made from a plastic called "polyvinylidene flouride", and can be purchased in spray cans and in pint, quart and gallon size paint cans. "Polyvinylidene flouride" or PVDF is a cross breed between polyethylene and teflon cuz it looks like:

...|
H-C-H
...|
F-C-F
...|
H-C-H
...|
F-C-F
...|
H-C-H
...|
F-C-F
...|
H-C-H
...|
F-C-F
...|

(pardon the periods)

If all the flourine atoms were hydrogen atoms, it would be polyethylene. If all the hydrogen atoms were flourine atoms, it would be teflon.

I'm presuming that a "3 inch head lap" simply means that each galvalume "W" shaped valley overlaps the one below it by 3 inches.

So, what we have is galvanized steel on steroids coated with paint on steroids.

Why would you call this a "minimum"? This galvalume sheet metal coated with Kynar 500 paint is what's used for the metal cladding on buildings and is super durable to exposure to weather. I'm thinking the only two metals that would outlast this would be stainless steel and copper.
So, why wouldn't ordinary galvanized steel be the "minimum" protection you can have in a shingle roof valley, bare galvalume a step up, and galvalume painted with Kynar 500, another step up, and then copper and stainless steel? I'm learning that galvalume painted with Kynar 500 is already a Cadillac flashing to have on a shingle roof, so I'm curious about your claiming it's the "minimum" you need.

3.
Quote:
The big things about valleys are what we call "tipping" the valley shingles. This means cutting the point of the shingle under the coarse that is visible. This stops water and debris from catching the top edge and running across the course, damming debris and causing a potential leak. This should be done on shingles and in a metal valley.
I found almost nothing about this "tipping" on Google. Is it also called something else, and can you link to a web site that explains how the shingles are cut at the valley and why cutting them that way is beneficial?
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Old 08-11-2009, 06:17 AM  
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Nestor,you don't have holes in the valley pan when you use a clip. A clip is merely a piece of valley metal that we cut about 1 inch wide and 3 inches long, you make a bend at the end of the strip and hook it over the edge of the valley pan, then you nail the clip to the roof deck. This will allow for thermal expansion, leave no penetrations in the valley material and will lay flat under the shingles. The valley pans are overlapped and not secured out in the open area. Securing them will pop the joints. I see people try and solder copper valley lap joints and the solder joints will pop under thermal expansion. If you pop rivet them pop rivets will also fail.

By using a painted metal for a valley pan you create a flashing that will last longer than the shingles. Remember galvanized garbage cans? You don't see them much anymore because they rust. Galvanized gutters will last a long time, IF they are coated inside and out with a red oxide primmer and painted. When you get into your heavy weight or lifetime shingles, the MFG require non-corrosive flashings. This is so that the flashings out preform the roof system they are protecting.

3" head laps are pretty much standard on any of your hard surface roofing installation specs.

As far as tipping valleys let me see what I can come up with.



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