# A question for the more knowledgeable



## JT Wood (Dec 17, 2007)

Can someone please tell me What is the best type of valley for a 2/12 valley.

I am mostly a carpenter, I am about to start an addition for a guy and he wants me to tie into the existing roof 5yr old

The problem is it will end up being two ridges side by side. So I am going to frame it to have the rafters lift an inch or every 2' as it goes back creating a slight slope.

Normally I use architectural shingles, then overlap them, with ice and water peel and stick in the valley. (Ive never had a leak yet.) But being such a slight slope, am I better to make an open valley with metal?

Or what do you guys recommend? I want to make sure I do it right the first time. I'll see if I can get a pic of the roof line too.

thanks guys:thumbsup:


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## OldNBroken (Feb 8, 2008)

An inch every 2' is not a 2/12 it is 1/2 in 12. If that's the case, You have to do the entire slope in a low slope membrane of some kind. Choices to look at would be Hot, torchdown or self adhering (see flintlastic SA) Membrane needs to continue minimum 2' beyond the valley going up the the other side, then shingled over it on that steeper side for aesthetics.


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## JT Wood (Dec 17, 2007)

Whoops:whistling

Yep, run will be 12' rise will be 6" sorry about that. (working too hard)


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## JT Wood (Dec 17, 2007)

It will look kind of like this. (Ignore the text I didn't write it) :w00t:


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## OldNBroken (Feb 8, 2008)

Your design is not going to work at all. You can draw that rise on paper but can't physically do it while still maintaining a symmetrical structure. Due to equal and opposite roof pitches, whatever you gain on the one slope, you gain the exact same amount on the other slope on the other end of your "valley". You don't want to find out your picture is impossible when you are sitting up there trying to figure out where you went wrong. 
Just frame straight into the existing creating what's called a "dead valley".
Over that you need to overbuild a full-diamond cricket. Then roof the whole structure based on the pitch you achieve with your cricket. If it's below a 3/12 then I suggest flintlastic SA on the cricket, continuing up the steep slopes a solid two feet, then coming back on the main roofdecks with shingles starting 2" above the valley lines of the cricket.

Does that say 3/8" osb? really? Minimum 5/8".


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## JT Wood (Dec 17, 2007)

That's not really my design, The guy knows it won't be symmetrical
It's a little hard to describe.

However when you say diamond cricket you mean like this?

I framed this house last year, didn't know these has a name.:laughing:


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## OldNBroken (Feb 8, 2008)

That is *exactly* what I'm referring to. Very good, won't have to explain it further. Everywhere that picture is not shingled, you are best to do in 3-ply Flintlastic SA. Then Shingle the main decks from the cricket valleys up.

Ya learn something new every day. The other idea won't work at all.


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## JT Wood (Dec 17, 2007)

It's a bit more of a complicated situation on this addition


When I get home I'll try to post a better diagram of what is there

I'm on the iPhone now

Thank renegade I'd give a thumbs up but I don't have emoticons on the phone


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## 1985gt (Dec 10, 2010)

Might be a better idea to frame it ridge to ridge and add a slight slope one way or another then use and EPDM, TPO, Torch or Hot mop.
With the design now I dont know if I would use a SA membrane even though they are ok for this applicaion and they for 1/4" or more per foot, You will have alot of water running in this area. I have used SA membranes before but never on an applicaion like this. If it was me I would use EPDM or TPO.


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## OldNBroken (Feb 8, 2008)

Use it all the time gt. Great product for small applications like this. Can also get close to matching shingle colors with it.


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## Aframe (Mar 24, 2008)

hughjazz said:


> It will look kind of like this. (Ignore the text I didn't write it) :w00t:



That valley runs in the wrong direction.

I would square/level across from the new ridge where it meets the house to the existing dormer and infill the triangle between the dormers. 
Then Rubber the valley. Leave it open at the mouth of the valley if you can so debris does not clog it up.


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## loneframer (Feb 13, 2009)

Hugh, If you cheat the slope on the overframe rafters, the cricket will have a roll to it. That may or may not be acceptable, but thought I'd point it out. I've done similar things in the past and just did a "half diamond" cricket.:whistling

The low pitch can get torch down, fiberglass mat/resin or poly urea/urethane, as well as probably a half dozen other roofing products that I'm not aware of. This house got the half diamond dealio up high and a quarter diamond in the corner of the porch roof, along with some elaborate flashing details.:thumbsup:


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## JT Wood (Dec 17, 2007)

loneframer said:


> Hugh, If you cheat the slope on the overframe rafters, the cricket will have a roll to it. That may or may not be acceptable, but thought I'd point it out. I've done similar things in the past and just did a "half diamond" cricket.:whistling
> 
> The low pitch can get torch down, fiberglass mat/resin or poly urea/urethane, as well as probably a half dozen other roofing products that I'm not aware of. This house got the half diamond dealio up high and a quarter diamond in the corner of the porch roof, along with some elaborate flashing details.:thumbsup:



Hey riz, The roof will be similar in principle to what you have, ( I was going to ask about this in the framing section.


The back of the house is a big gable the width of the house.

then the perpendicular gable that is existing.

Then the new addition is parallel.

I guess what I don't understand, is where the water at the back end (for lack of a better term) of the diamond is going to go? I'm having trouble picturing what you guys mean?:blink:


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## dkillianjr (Aug 28, 2006)

I don't have to much to add to the topic:laughing: But I will add another vote for the flintastic. I have used it a decent amount of times and had very good luck with it. And like renegade said you can get some colors and maybe match it better. 


Dave


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## kage (Aug 17, 2008)

We also use the flintastic in areas like this, no problems and most they blend right in..:thumbsup:


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## 1985gt (Dec 10, 2010)

Renegade said:


> Use it all the time gt. Great product for small applications like this. Can also get close to matching shingle colors with it.


Ive used the GAF product like it, Im sure its great but for me personally I dont know if I would trust it in a area like this, just leary of the seams is all. I do love the way you can get it to match (or close to) the shingles and install is easy peasy.


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## shanekw1 (Mar 20, 2008)

I saw that first pic, Hugh, and thought " Crap, that house is falling over!" Glad you put the second one up.

:laughing::laughing:


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## loneframer (Feb 13, 2009)

Hugh, here's a pic of what I typically do.

I usually lay a valley plate up each side and a plate at the top of the triangle, then fill in 16" centers from side to side, down to the point.

The pitch on the gable roofs doesn't change, the valley formed by the two roofs intersecting is level. I just over-frame the sloped area. If the main roof wasn't there and it was just two parallel gables, the over-frame would start high in the center and slope both ways. (Diamond cricket):whistling


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## JT Wood (Dec 17, 2007)

I actually suggested that to the homeowner tonight, I have 2 questions still,

I'm gonna need to be at least 5 1/2" high at the wide side of the diamond right?

Where does the water go that runs to it?

Here's a pic I wrote the text on it :laughing:


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## JT Wood (Dec 17, 2007)

this is an actual rendering of the project


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