Greetings
I’m building an addition to a very small cottage on Cape Cod.
The attached .pdf shows an exterior view from the gable end.
My questions are about where the old and new gable ends meet.
The existing cottage has exposed rafter tails and rake (about 10″ overhang), so we are matching that detail.
Where the old and new roofs meet there will be a V shaped valley for about 20″.
What is the best way to deal with water/snow in this area?
Is there some kind of cricket to build?
Thanks
Chris
Replies
Yes, build a cricket. You'll basically install a ridge 10" from each edge and run a roof to the outlet.
That is what is called a dead valley. It is a gauranteed leak situation the way ti its designed and must have a cricket large enough to divert water.
At a minimum 3/12 pitch, and 20' long, that means the 'cricket' will have a ridge 5' higher than the intersection between the two structures. It looks like you barely have that much room with the cricket ridge even with the ridge of the left structure.
You should also plan a good scupper to catch the large volumns of water than will come off at the bottoms of those valleys and guide it so that it does not damage the foundations.
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Piff, I think he said 20", not 20'.
Yeah, a plan view would have been worth a 1000 words.copper p0rn
Gents-
Here is a plan view.
The roof overhang is not shown, but it is 10", making the 20" dead valley.How high out of the valley should the ridge of the cricket be?
The roof pitch is 6.25"/12" (matching existing)Thanks for the replies
You don't need much. I used to cut them in by eye. Whack, whack, whack and I'd have the three parts (ridge and two pieces of sheathing) getting nailed in.
Not too high, not too low. Make it look good to your eye.
Not too pointy at the outlet.
Right you are!
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Piffin,
Out here it is called a hog valley. But dead vallley seems to be a better term, actually.
At 20' we'd be looking at doing a transverse ridge with 4 valleys - a huge cricket if you will. Your concerns are right on. At 20" we'd go with Blue's solution.
But I don't like these situations regardless of length.
Jim x 3
LOL, Hog trough more like it!;)
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alternative suggestion------
i would like to see the valley in person because what I am going to mention I don't know if I would do in your case
however-----
consider an EPDM pan
around here Ryan Homes--and some of the lower end builders built similar models where a valley would come down and just hit the corner of the house---was more like a four inch valley--if that--- rather than a 20 inch valley
what I have done a handfull of times--- is pull back the siding---- ( usually it's vinyl)-- loosen the corner post---and make an EPDM pan that wraps right around the corner.
anyhow- i have done it 4-5 times--- one of the houses ended up being featured in a FHB article for a different project the next year.
the first one of these I did--was maybe 15 years ago--and still working fine-- I expect the .060 EPDM to out live the shingles
anyhow-- just another option which you are free to disregaurd.
stephen
My experinece with these things is that because of it being mostly in the overhang whjere the roof is colder, there is more ice build up, so ypou create an ice dam that rises all winter, making it back under the shingles. In a moderate climate like the cape it might work with EPDM tho
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Piffen,
the pictures Joe carolla showed------- showed something much different than what I was thinking the OP was describing in my area---- a dead valley or a blind valley referrs to a valley that terminates against a wall. the valley Joe showed---wouldn't cause me a minutes worry----- it's really common around here on "ranch" style houses where the garage is a bit offset from the house we get a thing here called "lake effect snow"--- so the weather is nasty,snowy icy--anywhere from thanksgiving to the first week of April----and very slightly to my north east--it's even nastier joes Valley--would not be a problem
stephen
against a wall or another roof, either way, the water sits there dead instead of flowing, thus the dead valley term
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well to me- a blind valley or a dead valley--has no real exit.
the valley joe showed-- actually has 2 exits- they aren't good exits- but they are exits--one over the gable-and one down the roof it's really no different than having a pan behind a single flue chimney that would be 20 inches wide or so I would NEVER put a cricket behind a single flue chimney-wouldn't be needed.
stephen
it's really no different than having a pan behind a single flue chimney that would be 20 inches wide or so
We always put saddles behind every chimney; even the 20" ones (do they really exist?). I wonder now if we were following code or following the boss's tradition?
I've done a lot of 20-24 inch chimneys with no cricket too, but it depends where on roof it is located and the climate it is in.At the bottom of a long roof, I have sen 4" of water pile up behind a 24" chimney in a heavy rain
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blue, we very rarely see a cricket here and when I do see one--almost invariably-- the cricket has rotted---and frequently the board underneath so--- on the rare occasions i find a cricket--- first thing i do is tear it out and throw it away despite what piffen says-- i think it's physically impossible for a 4 inch deep puddle of water to pond behind a 20 inch wide chimney do the math---20 inch wide chimney-- water only has to travel 10 inches to reach one of the sides--- it simply isn't going to pile up 4 inches deep here-- I generally make a back pan out of 24 inch aluminum stock---actually the last few years I am much more likely to use 18 inch wide stock as I can get THAT in an even thicker metal my upturn--is four inches--making the pan either 20 inches high--- or 14 inches high-- I extend the pan 4 inches beyond either corner--- so the pan for a 20 inch chimney--will be 28 inches wide---- I bend the corners down at a 45 degree angle--- the 4 inch high upturn-protruding 4 inches beyond the chimney--makes this easy so now the water has to travel 14 inches to get around the chimney---- but then it drops entirely clear of the sidewall typically-- i will shingle up to within a few courses of the bottom of the chimney- then the front, sides and back of the chimney get wrapped in icegaurd-- the front edge laps out onto the top half of the shingles---and is covered by the last few courses if you really want--- you can but another course of icegaurd above the rear pan lapping down onto it---- look at velux skylight flashing kits-- they usually spec this detail--and a Velux flashing kit back pan------doesn't go 20 inches up the roof---- it doesn't have a cricket either--and 4 inches of water doesn't pile up behind it think it through--what are the entry points--water/ice could magically pile up above the upturn------- but with a cricket---you still have the upturn--only now it's a side wall
water could enter at the 2 back corners-- but my corners extend 4 inches beyond the chimney---and actually form a roof over those corners---- compared to a cricket--- that forms a valley that ends at exactly the corners- VERY leak prone---plus you have the ridge/roof intersection which means----- water actually has ONE more entry point with a cricket----and 2 other entry points that are more vulnerable than without a cricket if crickets were so great--- I wouldn't find most of the few here---rotted RE: our climate-- perhaps much like you had in michigan?---- frequent temps in single digits------ below zero once or twice a winter------- occasionally as much as 2 feet of snow on the ground----- but rarely much more than 10 inches---a lot of ice storms, freezing rain- miserable from november untill april?-sound familiar?stephen
If the cricket will rot, a plain flashing will rot faster Steven. Both are the same material, but the cricket sheds water while the plain can hold some of it." despite what piffen says-- i think it's physically impossible for a 4 inch deep puddle of water to pond behind a 20 inch wide chimneydo the math---20 inch wide chimney-- water only has to travel 10 inches to reach one of the sides--- it simply isn't going to pile up 4 inches deep"You only think it impossible because you have never seen a torrential downpour or been stupid enough to stay out on a roof in one.
I have seen rain so hard that every horizontal surface has water an inch deep within twenty minutes. been driving in it where there is enough water remaining on the hood of the car to see raindrops make splashes as they hit, and where wipers on high speed re not doing the job of keeping up so you have to pull over because you can't see where you are driving thru the windscreen and even if you could see thru it, you can't tell just where the road itself is.take that kind of rain where it is coming down at a rate of three inches in an hour..That is 1/4" in five minutes or an eighth inch in 2-1/2 minutes.And a roof that has twenty feet upslope of the chimney means that you get 2-1/2 inches of rain depth there in that two minutes. Believe me that when that rate continues, it is impossible for it to shed sideways fast enough to drain out without pileing up deeper. Remember that the drain size at the chimney corner is a tiny triangular space that only gets larger as the water depth increases.I've been up there and seen it happen. That is why a flat flashing needs to be a min 8" high behind a chimney and why a cricket is better. It divides the flow instead of letting it try to puddle and eddy before flowing sideways.Add a pile of leave debris there in that flat flash job and you compound the problem, both with water flow and with the flashing rotting faster than the cricket.
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Remember that the drain size at the chimney corner is a tiny triangular space that only gets larger as the water depth increases.
I always ran the cricket wider beyond the edge of the chimney.
I was talking about the plain flashing fitting tight to the chimney.
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nonsense piffen,
a cricket is wood not the same material as a back pan---which is a non ferrous metal--- not going to rust through but a rotted wooden cricket--- means that the flashing leaked---- why would the flashing leak?----- well a cricket un-necissarily adds seams and joints to the flashing--which WILL leak---compared to a seamless back pan as far as your melodramatic version of how much water these things need to handle------ not so-----certainley not so here.
I have NEVER seen a back pan here 8 inches on the up turn--and they don't leak---so your statement that they need to be 8" high--not accurate. I made a rough calculation years ago-- of how many roofs I had been on at that time----- not necissarily personally roofed-- but climbed in order to repair,or estimate, or inspect.-- At that time-well over 3,000 MAYBE 20 or so of those roofs--had crickets-----and most of the ones we eventually roofed--- crickets were rotted out I should clarify something I said about an 8 inch up turn--- I have seen a few where guys bent an 8 " upturn out of a 24" piece of aluminum---and then Karnaked it to the brick.-- those leaked--- but not because water somehow magically rose 8" vertically---but because there was no counter flashing--- and rain down the chimney backside ran BEHIND the pan--- the upturn could have been 80" high--and it was gonna leak as far as the velux flashing kits go--- they are in fact a pretty fair comparison to chimney flashing.- I have 5 of them on my truck right now for a project starting Tuesday------ no where on the packaging does it say" make sure you only use these high up the roof ,cause we think Piffen says they might leak lower down the roof!"---;>) Stephen
obviously you don't get heavy rains there, so your advice doesn't apply to areas where we do.
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View Imagecopper p0rn
Have you ever seen a wood cricket?
Or do you use metal?I wouldn't expect a wood one to do much good.
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Metal. Solderable metal.
I think Haz is using alum, so he has to rely on caulk for cricket flashing joints.copper p0rn
My point ios that a piece of wood is just there for shiming as support sometimes.Since Steven does not see or use crickets, how can he say they rot out? The wood is just support and the metal itself is the same material as a flashing would beSo yes, if he has to caulk the cricket metal, that might explain his predjudice.But as good of a roofer as he is, his experience is limited to one very narrow area of roof style and material and climate so it can't be expected to apply to other places, climates, and materials.
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We have wood crickets, we always cover with grace or simular then shingle if you can.
I have seen the metal crickets, just not done many of them.
Wwell, ifthat is whaat SH is thinking, I can see his displeasure. Thaat would be a foolish way to do behind anything smaller than about a 6' chimney
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"a Velux flashing kit back pan------doesn't go 20 inches up the roof---- it doesn't have a cricket either--and 4 inches of water doesn't pile up behind it"skylight comparison is not apples top apples for at least two reasons.One is that a skylight is normally high up in thje roof area so there is little rain running to it from above, while a chimney that needs a cricket is more often near the bottom of the slope where a lot of runoff is flowing to it at velocity.a skylight that does get water piling up behind it that deep is letting it cascade up over the glass and on down the roof, while a chimney presents a solid damn where water can seep in over the counter flashing reglet cuts.velux skylights do have a return bend in the top base flashing for the very purpose of stopping the water than backs up that far, a recognition that it does happen.
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I think ponding is the anomaly that would dictate whether a diverter cricket is necessary for the (Gable valley ?) dead valley here. I don’t think there will be any ponding and the adjacent roofs would have close to the same pressure of runoff to each other so I think 32” of uncut flashing should do it.
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I do not agree that single chases chimneys are fine without crickets. They are SOP for me and will remain so.
Would you leave it as a 20" "v" or put a saddle (ridge) in it?
Personally- i would leave it as a 20 inch Vee--and there would be zero problems. several years ago- i posted a zillion pictures in a thread"welcome to stephens neighborhood"- something like that? several of the houses I pictured had roofs we did with similar situations- never a problem.
I admidt-- it isn't ideal---- but it isn't a problem A common house style here--has rake coming down and intersecting the porch from 2 sides--never a problem-also similar situtions--main gable comes down--but the bottom of the gable is held maybe one inch above the lower roof--- the lower roof is shingled and step flashed right under it like usual-never a problem these are all houses i see almost every day with in a few blocks of me--- zero problems-- if there were problems-- i would hear about it--but they just are not problems.
gotta run-----dog wants her morning hike
Stephen
Your plan view and left side view shows no valleys at all. You just have about a new 7' gable end butting into your existing gable end.
Joe
Although the buildings themselves don't overlap the plan view does not show the 10" roof overhang on both the existing house and the addition. This is where the valley occurs.I'll go with the small cricket idea and loads of Grace I&W to divert the water off either side.Thanks
You have 10" fly-rafters/gable overhangson the existing house and addition?
Joe Carola
Here are a few views.Joe Carola
Joe
These pictures are exactly what I am dealing with.
Thanks!
Chris
Joe did a nice job of showing a proper cricket for your situation!
OK-So I built the cricket today like Joe's pictures show.
What is the best sequence of flashing??
Grace first? Aluminum? Lead?
Thanks for the guidance
I&WS 1st. I'd use a metal you can solder sonce there will be joints in it.copper p0rn
You're gonna light up Steven and Paul again !!!
I'd have done it the same way as you, but since he's built this nice cricket, he needs to do it justice.copper p0rn
I agree , shingles on that cricket isn't the answer .
Have a great day . Heading back for more copper eyebrow work today .
Make that three. It's a waste of time to shingle that
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Theres no need to use a cricket for this . Bend a 3' wide piece of metal to conform to this small trough . Use drip edge on either rake and lock the metal to it .
Leave 9" exposed on each side . It will never cause you problems .