Good afternoon. I have a quick question about step flashing.
This Fine Homebuilding article https://www.finehomebuilding.com/how-to/departments/building-skills/installing-step-and-corner-flashing-on-a-roof.aspx shows that the step flashing is only sealed at the bottom and top course.
My question is:
If shingles have tar strips on every shingle to protect from “wind driven rain,” then why isn’t every piece of step flashing sealed underneath?
Edit:
P.S. In another forum post they disagree about nailing to the wall. Any thoughts on this either? Wall seems better to me, as the housewrap would lap and cover it.
Replies
The tar strips don't protect (much) from wind-driven rain. They prevent the wind from lifting the shingles and tearing them off.
Before the strips were common practice most roofs around here of any age would have several shingles missing after 5-10 years. Now you hardly ever see that.
So you think putting a bead of caulk on the step flashing is unecessary? (It won't tear off in the wind)
At the top and bottom, using the techniques shown, you're not getting the full overlap that you get from the other step shingles. So the caulk helps prevent blow-in in those areas.
Kevin
Here in NW Oh, there's a flexible step flashing offered (sort of a corregated pc, that bends around things real nice. It would be perfect for that starting corner flashing.
and around here, not many even start with that style of corner detail shown in the article you linked to. Then again, there's not many roofers who happen to know flashing worth squat. A shame, because it's part and parcel to roofing.
If you so use caulk as recommended, don't use cheap stuff. Most here will use roof cement in a tube. However, if you can find it products by Geocel are good, a clear sealant called Through the Roof, or any Urethane caulk.
The rest of the stuff can't take the heat.
Awesome, thanks for the advice guys.
I've been using http://www.gardner-gibson.com/linedetails.aspx?id=15 "Black Jack" #99 I think. It's neoprene, which is weird.
I also used a bit of DAP http://www.dap.com/product_details.aspx?BrandID=29&SubcatID=6. DAP makes two roofing caulks, I think I used the one linked which is polyurethane.
I'll keep an eye out for geocel and Through The Roof, but I don't think I've seen them distributed locally.
kevin
www.geocelusa.com/php/oic/index.php
www.sashcosealants.com/Home_Improvement/Through_The_Roof.aspx
Use these links to find the local distributor-Ace Hardware probably can get geocel, probably the same is true for the Sashco products.
Good stuff.
I found a local place that was "supposed" to carry it, but they don't.
I'm gonna buy a couple tubes off Amazon and check them out.
Is the 3300 what I want?
http://www.amazon.com/10-1OZ-3300-BLK-POLY-SEALANT/dp/B002M8JBBM/ref=sr_1_8?ie=UTF8&qid=1298390543&sr=8-8
I'm going to have to check prices, but $5.99 a tube seems like a decent price.
Edit:
It looks like the 2300 is the higher grade product, is this correct? I knew $5.99 was too cheap : X
http://www.amazon.com/Geocel-2300-Clear-Tripolymer-Sealant/dp/B003F1MC3Y/ref=sr_1_5?ie=UTF8&qid=1298390812&sr=8-5
$8.99
I've used the 3300
but take a look at this-
http://www.geocelusa.com/php/oic/product.php?prdb_product_id=12&prdb_category_id=30
and
http://www.geocelusa.com/php/retail/product.php?prdb_product_id=84
When you do your reading, remember that you should know what you're using it on/with-and look for compatibility.
For instance-you wouldn't use a solvent based caulk on a rubber roof.
and also, in most cases roof cement in a tube does quite fine bedding shingles.
It's when you start getting into areas that "show" that you drift away from the roof tar and look to clear sealants.
But, roof cement can and will dry down and lose adhesion.........
Kevin
I'll jump on the 2nd part of your question 1st, I go with nailing the flashing on the wall, high and tight.
As the article says, the building paper and siding will cover those nails, but I like to use a strip of Ice and Water (Grace), or Vycor running up the sidewall and lapping over the step-flashing nails about 1", then the building paper and siding. Since you will be replacing the roofing before you ever have to replace the siding (hopefully) it makes more sense to me to nail to the sidewall. This way you can strip out the roofing and still re-use the old step-flashing by simply bending it up slightly to slip the new shingle underneath.
Also, using the I&W allows the nails used to fasten the siding to self-seal, helping to prevent water intrusion (rain splash,snow melt etc.) at those points as well.
The caulking at the top and bottom is needed because you are changing direction with the flashing and not running a continuous straight line, as you are from bottom to top, you have compromised (slightly) the water shedding capability by cutting the flashing so the caulk acts as a back-up seal.
Just my 2cents worth
Geoff
I'll add more change to your 2 cents.
to remind Kevin to hold the siding up at least and inch and a half above the shingles. Use colored step flashing if the silver bothers you. Seal all siding / corner boards very well along that cut line as well as back priming. I'd add kick out flashing at the bottom of any dormer/chimney chase / sidewall application.
kick out flashing
What is kickout flasing?
What is kickout flashing?
Lemme see if I can find an already explanation, description or photo..........................
Here you go. http://www.kickout.info/
Good to know and apply on all roof/wall junctures-including chimney chases.
OTOH, if you nail to the roof and don't nail to the sidewall then it's easier during reroofing to move the step shingles slightly to align with the shingle rows.
The step flashings should be nailed to the roof at the very top of the flashing. The next step flashing and it's corresponding shingle will cover that nail. If you nail any lower than that, the nail can penetrate the step flashing below. I've roofed for nearly 30 years now and I can probably count the number of times without removing my shoes that I've found step flashing in truly re-usable condition. If it's nailed to the wall, it's tough to remove/replace the steps without boogering the siding.
hmmm
I'd consider that a workable and adequate but somewhat sloppy flashing technique myself. I would not trust it without it being backed up by ice and water shield rolled up the wall behind the flashing.
2" is just no where near enuf over lap except in dry desert.
And I try not to nail thru the step flashing. I pinch it into place by nailing immediately next to the metaledge so the head of the roofing nail is over the metal. If I have to nail into the piece, I nail it high and in the roof, not the wall