I have a roof valley where a small 4/12 pitch roof arrives from the left onto a 2/12 roof that is from the front to back, the back being higher. This valley is 19 feet long and I can tell that the bottom five feet of it has a very troubled history. The last roofing job of asphalt shingles to create a cut valley has been a disaster. It appears that water flowing from the left flowed over the cut edge and onto the 2/12 roof (which has a lot of water on it already flowing downhill) in a sideways direction that found its way under shingles and did damage to a complex soffit and the sill it rested on as well as the roof deck and three rafters. I’m going to try to install a “w” type metal valley . How wide should it be on this low slope roof? I’m thinking 16 inches from the kick up in the middle to the outer edge with one shingle tab running onto it. Anyone? Thanks for your time and consideration
P. S -The roof was originally barrel tiled
Edited 11/25/2006 11:56 pm ET by Islagrande
Replies
It sounds like the problem isn't the valley per se, but that the 2/12 slope is shingled.
The shingles on the 2/12 need to be removed and a different roof installed (I would want EPDM, but others here might prefer something else). The new roof membrane should go through the valley a ways with the shingles on the 4/12 only coming to within maybe two feet of the valley.
But I've been wrong before.
Rich Beckman
This signature line intentionally left blank.
ditto what rich said.
BTW----------personally i might go with a modified bitumen system. Certainteed makes a nice one color matched to their Landmark shingles. A 3 ply system would be pretty near BOMB proof----and it installs much like icegaurd.
I switch back and forth between EPDM and modified bitumen.-- In------- some situations EPDM gets the nod--in others the modified works better.
Depends on visibility, roof configuration, anticipated flashing details, LANDSCAPING, foot traffic etc.
Stephen
Thanks very much for your reply. I do skylights for people and I have a high success rate. My first in 1986 is still in service with its homemade flashing and glass from a medicine cabinet door. I tell people to think the way water thinks. I see the results of laziness, earnest but unknowing efforts, and people who have contempt towards the work. What I saw here was the local handyman layering five layers of shingle on top of a 14 inch wide strip of aluminum sitting on six layers of light tar paper. The water flowed off this built-up valley and on to easier and lower surfaces. I was wondering if I could trouble you for one more detail.
You mention that a three ply system would be bombproof? What system is that? Here in Florida I recently found a source for RW Grace snow and ice shield ! Also of the two types of roof membrane you mention, is one more suitable for going around a skylight curb than the other? I attach two photos now, of the failed valley. Thank you for your time and consideration. Thank you to RichBeckman as well
Did I see right that the cut side of that valley goes up the roof in the second pic? If that is the case then I'd definetly be redoing that valley.
You mentioned Florida. Without the snow you might be alright if you ice and snow the valley and then go with the metal W valley.
My .02,John
J.R. Lazaro Builders, Inc.
Indianapolis, In.
Here are the pics resized.LOL!! Nevermind! I screwed it up!Rich BeckmanThis signature line intentionally left blank.Edited 11/26/2006 3:08 pm ET by RichBeckman
Edited 11/26/2006 3:09 pm ET by RichBeckman
There are two major problems with that valley.The first is that composition shingles should never be installed on a pitch of less than 3/12, with 4/12 and greater being optimal.The other majopr error is thaat the lapped valley is lapped the wrong way - the steep pitch should always overlay the lower pitch to work with mass of water flow. Ooops, now that the second photo has downloaded, I see a third, which tells me that whoever laid these shingles had no idea whaat he was doing. The lower pitched side not only is laid facing hte wrong way, it is not cut at center of valley, so that it faces UPHILL inviting water to come on in and pay a visit.To have any slight chance of success withthiss roof, you need to remove all the shingles, apply ice and water shield, and shiungle with vlleys done correctly. I would also lay the low pitch with 4" exposure instead of 5"BTW, it is best when posting photos on the web or sending viaa e-mail to keep them edited to a decent size to avoid choiking the bandwidth. If it were not late at night and I watching TV, i would not have bothered with such a large file
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Thanks very much for your post. I was not aware that the attachments were bloated and I will correct that . When I first saw that valley, I thought for a moment there was a new understanding of water that I wasn't aware of. The opposite valley is done in the same fashion. I will take your suggestion to reduce the exposure to 4 inches if I do any repairs with tabbed shingles. I drove around this town in Florida and looked for other houses this developer built in 1958. People with this same roof plan have done this shallow portion of the roof with roll roofing or the tabless 50 years shingles with a cut valley. I would like to put in a metal valley. I will also take your suggestion to be generous with ice and snow shield.
The current valley was made thick with tar so the water flowed off it and into the field. The damage to the final four feet of that roof is extensive, rafters, soffits, roof deck, drywall/plaster cieling, the beam on which it rests and even the columns holding it all up.
I started out roofing for three years in Florida. That type hopuse with low pitch is common there, but they were usually originally roofed with BUR tar and gravel. It takes a certain amt of skill and equipment to do that sort of work, so a lot of folks found ways around it, not alll with good results.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!