Open Metal Roof Valleys

[gdavis]

We are having a lot of problems with leaking roof valleys. It is not just one contractor but their method may be similar and wrong.

So what is a good method for installing open metal roof valleys? Here are two scenarios now in debate:

Ice and Water shield (36") goes over existing felt shich terminates in the valleys. Ice and Water Shiled is layed down the center of the valley over the felt. Then an 18" piece of copper with standard W shape is layed over that.

OR

Ice and Water shield goes down first, then felt is laid up the roofs and terminates at the valley (over the Ice and Water shield) with the copper going over that.

The position of the Ice and Water shield (or 90 lb roofing) is the question.
The new home builders seem to put it on top because the framers have already felted the roof. But does it work better if it is placed down first.

Mfg. illustrations seem to differ.

Problems occur with wind blown rain.

Anybody got the last word on this?.



glenn

[Allan Edwards]

Re: Open Metal Roof Valleys

I think the Ice and Water shield goes down first, then the roofing paper, then the metal. That's how my roofing contractor does it.

[Dick Seibert]

Re: Open Metal Roof Valleys

Glenn:

I&W goes down first by my carpenters, around perimeters and down valleys, then the tin-men come in and cut, solder, and install all the copper, the valley metal is cut but tacked loose for the roofers. The roofers then set the valley copper and lay their felt on top of the valley metal. If roofing felt is installed under the valley metal, then water can blow (especially on 4 in 12 pitches) under the copper. After the roofers leave the tin-men come back and install the counter-flashing and check out everything the roofers have done at the metal/roofing junctures. Here is a picture from the Shake and Shingle Bureau.

[Dancing Dan]

Re: Open Metal Roof Valleys

Either way, you can also add a strip of roofer's cement to adhere whatever lays over the copper (either the tar or the shingles) to it.

[Loren97]

Re: Open Metal Roof Valleys

One guy that I worked for put the I&W down first, 36" either side of the valley with a slight overlap, then put the metal down, ran felt up over the metal and then I&W over the metal and felt to bond with both leaving the center of the metal exposed. Seemed like an incredible overkill, but I can't imagine it leaking for a long time.

[cmm_88]

Re: Open Metal Roof Valleys

How is the valley flashing fastened? I typically require the edge of the valley flashing to have an up-turned hem/receiver. 2" clips at 12"o.c. are then hooked onto the valley flashing and nailed to the roof deck. This small hem acts as a dam and limits the wind blown rain. It also tends to stop ice dams from moving past the edge of the flashing.

As far as the I&W / Felt, I install one 36" wide sheet split in the valley then cut a sheet in half and install an 18" strip on either side. Then I run the felt paper over the I&W approximately 12". Valley flashing goes over it all.

9" past the edge of the valley flashing (14"-16" total) seems like a long distance. Are the adjacent roofs two seperate slopes?

[Andrew R.]

Re: Open Metal Roof Valleys

Glen,
I'm surprised you guys are using metal down there. Weaved or overcuts are the standard here for shingles, shakes are the only thing we use valley metals. I've never had many valley problems. I have heard the metal valleys don't perform well in wind.....like today, geez you would think we are in a hurricane.

[gdavis]

Re: Open Metal Roof Valleys

Like, Allen, I thought that I&W would go down first, then felt, then copper over the felt.

I see that there are many ways to do it. Seems the popular way here is to put the I&W over the felt and then the copper over the I&W. I can tell you that this arrangement leaks almost without exception. In hurricane winds you can collect a couple gallons of water in 24 hours. I believe that the only way this is possible is that the water goes across the copper, across the I&W and onto the felt then comes back and sneaks under the I&W where it is no longer stuck down.

I also noticed that they do not take the copper over the ridge. That, I believe, is an absolute MUST. Flatten it out at the top and lay it over the ridge and lap in the other side the same way.

I apprecieate all the input. But does anyone have the Word of God etched in stone on this?

When I try to just use my own head, I come up with this:

Laced valleys almost never leak.
Roofs almost never leak except at flash points.
So, I don't worry about water leaking through the main roof and scooting under the copper. I worry only about water leaving the copper and running under the main roof. Sooooooo , I put the copper on top and only lap the shingles over it.

I put the I&W shield below the felt because the felt is coming from two different directions and either butts together there or laps over. The felt is more prone to leak in valleys than in the field of the roof. If it leaks in a valley, I have I&W sheild under it and wide enough to take the water to the eave even if it fans out a little. So, in my opinion the I&W must go under the felt directly on the sheathing. Then the felt. The copper must go over the felt, and the shingles lap over the edge of the copper. That seems pretty logical to me.

That is my independant thinking, but the methods and details seem to vary.

The roofers put the I&W over the felt because the carpenters have already laid the felt and they don't want to take it up. (My thinking is that the roofers should come and lay all the felt too, but they don't). We don't have separate tin men. The roofers do the flashing.

These open valley roofs are required in an upscale neighborhood because the architects like the way it looks. There are many homes with shakes, clay tile, and slate in this neighborhood because that is all they would allow initially. They've just started allowing fiberglas shingles but they want those metal valleys. But It seems to be a real problem. I am currently working on a cure for multiple homes done by different contractors where all open valleys are leaking the first time it rains. The roofers slow it up enough to get off the hook by running a bead of silicon down the edge of the shingles at the copper. Wonder how long that will last?

If you look at the Certainteed detail, the I&W goes down on the plywood and then the copper , as I interpret it. But the intepretation is vague becasue there is a note there that says the "felt is omitted in the sketch for clarity". What a hoot! (The ommission is causing the confusion.)

Thanks,

glenn

[Bill Robinson]

Re: Open Metal Roof Valleys

I have uploaded a couple of "approved" details.
In my experience the valley flashing goes down first, then the metal and finally the felt. Followed by the shingles.

It is critical that no nails go into the metal if the nails can be exposed to rain or wind-driven rain.

Of course the valley flashing must have "returns" to deflect the water.
What is different about the tile roofing assuming it doesn't leak?

Interesting on the look, I am seeing closed valleys for tile are the preferred look in developments here.

The difficulty is that a closed tile valley is more prone to leaking.

Are you able to implement the necessary changes to stop the leaks Glen?
Bill R

[gdavis]

Re: Open Metal Roof Valleys

Bill:
My role is to work with the contractors to identify the problem, then review their proposed solution on behalf of the owners. During the repair work, I will inspect the work in progress.

Almost every detail and every comment so far has required that the I&W go down first. I believe that this is essential.

There is about a fifty fifty split on the whether the felt goes under the copper or over the copper. My thinking is that if the felt goes under the copper I have a watershedding surface both under and over the copper. The shingles will also stick better to the copper.

I'm still evaluating and pondiering the options

Thanks for your input.

glenn

[Dick Seibert]

Re: Open Metal Roof Valleys

Glenn:

Think about it, the felt always goes over the copper. Water is running down the felt (the shingles are cosmetic) and it should be dumped into the copper. If the felt is under the copper the water is dumped under the copper onto the I&W.

[Doug M.]

Re: Open Metal Roof Valleys

I agree with Dick. Always look at where the water is coming from (uphill) and try to send it back to the roof surface as quickly as possible. I&W instructions say it should directly contact the roof sheathing. I once asked a rep about if it should go under or on top of drip edge when used as eave protection. He told me to contact the roof sheathing and put the metal drip edge on top. That's against logic (push water back to the top) but that's what he said.

[Andrew R.]

Re: Open Metal Roof Valleys

I have a feeling that most of these valley leaks will be roofers not dubbing a couple shingles.

[Dick Seibert]

Re: Open Metal Roof Valleys

Glenn doesn't say what kinds of roofs these are, but on roofs like cedar shakes it's an impossibility to place the interlaced 30# felt under the valley metal. I still interlace 30# between between flat tile over the I&W, not many do it anymore, but it gives a much better roof because the interlaced layer takes any organic materials (like oak leaves which we have a lot of here) and allows the deterioration to occur in the interlaced layer rather than the base layer or I&W. In the areas under oaks it's easy to remove some tile every 10 to 20 years and replace the deteriorated interlaced layer and the base layer remains as good as new.

[gdavis]

Re: Open Metal Roof Valleys

Dick and Doug:
I don't think its that simple. Consider this.
(BRW, we have asphalt (fiberglass) shingles.

If you put the felt OVER the copper (with the shingles), what do you have to prevent water from seeping under the felt? Roofing cement, caulk? I hate to rely on that. Dick you don't like to rely on caulk, so what do you think?

If the felt is below the copper, then you have a watersheding surface both above and below the copper.

Doug:
You are a assuming water only flows downward. In 130 mph wind, water flows upward as well. That is the problem I think. We don't see the leaks unless the wind is howling.

In fact, I expect that the shingles on the entire roof will leak some in hurricane force winds. I know that the overlap of the shingles needs to be such that the water would have to climb vertically to top the shingle below the one that it is blowing under. Wind blown rain at the design wind speed can blow over 3 inches vertically. So, factoring in the pitch of the roof, I need more than three inches of VERTICAL overlap (four to be safe). So there is some lower pitch limit where wind at 130 mph will leak through regular shingles. 3:1 slope required by code is fine in 80 mph wind zone for most of the US. But in the hurricane zone, I'm thinking that this is not enough. I"ve wondered the same thing about lap siding. The mfg desing for 80mph and forget about us folks in the hurricane zone. Or, do they decide that 3 hurricanes per year is not frequent enough to worry about and things will dry out between hurricanes and not rot.

There is another problem not yet mentioned. There are two intersecting gables forming a valley on the front of most of these houses. There is a shed roof over the front porch. The end result is that the valley changes pitch about half way down the roof where the slopes meet. Now, how do make the direction change and not create a leak? The valley flashing is W shape. The roofer suggested that the lower vally go past the upper valley and the upper valley lap over. I still listening, but I'm also thinking about a fabricated fitting to make the turn. Otherwise, water is either goint to get in while coming down, or while blowing up. I don't think anyway considered this when they designed open valley details.

Please contiue with your responses.

glenn