How do I flash the intersection of a wall and a shed roof? The last course of 3-tab shingles came out where I had to trim 1/2″ off the back to butt them against the wall and have them hit the next row in the right place. I got some galvanized L flashing and un-bent it some. If I put that in place, it comes out just uphill of the sticky strip on that last shingle row.
So that’s where I am. What next? Do I cut down another row of shingles to just tabs and put those down before the flashing? Or do I put down the flashing and nail down the cut off row of shingles on top? Asphalt cement on the nail heads? Something just seems wrong with nailing through the flashing. But I guess I’m getting the wall water on top of the shingles? But won’t water just build up on top of the flashing in that pocket formed when the sticky stuff seals to the top cover-up shingles?
Maybe I do both? More shingles to cover that sticky strip, and then a duplicate row to cover up the flashing.
This flashing is not pretty. I sure hope I’m not supposed to just leave it exposed. My Architectural Graphics Handbook shows it like that for copper roofs, but surely that’s not right for 3 tab fiberglass reinforced asphalt. I hope.
Thanks for advice,
B
Replies
Just to get the ball rolling....
"Do I cut down another row of shingles to just tabs and put those down before the flashing?"
That's what I would do.
Then I would install the flashing.
Then I would cement cut off tabs over the flashing to hide it, no nails.
Roofing cement does not hold up if it is exposed, sunlight degrades it rapidly. I use butyl rubber anytime I need to cover a nail head or otherwise have sealant exposed.
I don't see how you can go wrong with the above, but...
I'm still learning myself....
Rich Beckman
Sounds good. I pretty much decided on that same tactic in sleeping on it. I figure if Iearn a better way later, I can always pull off the little pieces and change things so long as I haven't punctured the flashing.
John Carroll already told me to get the flashing bent to the right shape at the sheet metal shop. My husband vetoed that and insisted on flattened out 90 degree stuff.
I let him have his way on the roof because he paid for the shingles and carried a lot of them up there, but now he's not here and I'm on my own. I'm just trying to zip it up before the next rain.
Now to figure out this hideous plastic ridge vent.....
B
Any of those options will work with a little adjustment.
Here's what I usually do; I would install the flashing you have (You've already sprung the angle so that it will pressure itself to the roof and wall at the edges) Lap the ends by about 4". Then use roofing cement to glue the tabs over it. Now in some locations the heat will allow them to slide around and down so I use 4d galv fine or 4d SS ring nails to pin them in place. Then I use clear butyle or Geocel caulk to hit the nail heads. Roofing cement will be cracking up on the heads in three or four years and is more messy.
Flashing totally over is the most weather resistant for the long run and can be better looking if it is custom formed to the pitch and has a crimp at the edge to help hold it straight. That way it is only nailed at the wall edge and not down through the shingles. More common with slate and cedars.
Now this flashing needs to be in behind the siding and it's underlying screen. If the wall is sided already and you can't break into it easily, there is still hope. But it relies on trusting a pair of caulk beads, not something I care to do except on garages or sheds.
Thanks for the reasurrance! That's how I did it. It was over 90 degrees today, but the plastic roofing cement I used held the little tabs on the flashing just fine. It looks just OK. I'm not going to post pictures and brag how good it turned out. The flashing should really have been bent properly.
How many nails are you supposed to use on flashing? I've been using one per on step flashing, and about one every 2 feet on the long stuff. Is that enough? They leave out these details in all my books.
I have the siding off the wall above the roof. I slipped the flashing behind the tar paper that's up there. It's all pretty torn up. Been there a while. I think I might ought to take it all off and put up fresh before I put on the Hardi Shingles. I had to do that before I put shingles on the roof. I figured I got my money's worth out of that 15# felt considering it was up there about 9 months. Long enough to pull half the plastic cap nails through it and turn the rest of them brittle. I got them all pulled out in no time, though, and started over.
I think that I remember you posting a Q back then about nailing pattern so the wind won't blow it off.
I sometimes nail as far as three or four feet apart if I think that it needs to move. An application like this, I might nail every foot OC. For flat roofs it should be nailed every four inches. Reason is that the metal will have a high degree of expansion/contraction from thermal movement. A seal on a flat roof cannot be allowed to move and braek the bond. In other places such as yours, appearance is a factor. If the metal expands and isn't nailed tight enough you will see wrinkles in it. The most obvious example of that is where someone uses aluminum eave edging and nails it about three-four feet apart, then on a hot summer day, little mountains appear.
Excellence is its own reward!