Home>Discussions>EXTERIORS>Roof Valley replacement without reshingling complete roof
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John Oosterling
Re: Roof Valley replacement without reshingling complete roof
keith3267 wrote:

I agree with painting the valley before it starts to leak. If the flashing is galvanized steel, then I would suggest the following. Clean the whole valley with a degreaser and let dry completely. Sand to bare metal only where there is rust. Do not damage any protective coating that is still working. Treat the bare metal with a phosphoric acid product like Por15 rust converter. This makes an Iron Phosphide coating that is very effective in preventing future rust. Dry the area with a heat gun or hair blow drier. As soon as it is dry, use a zinc rich primer like a Zinc Chromate on the repaired areas. Then coat the whole valley with a primer and follow with a coat of paint to match the shingles.

If you accidently sand a hole in the flashing, complete the steps through the zinc chromate. Then use a metal filler like JB Weld to fill the hole. Then prime and paint.

Edit: use a spray can for the zinc chromate, but a brush and/or roller and tray are OK for the final coat of primer and paint. You can work a little paint under the edges of the shingles with a brush.

Thanks for your reply very helpful indeed, John

Re: Roof Valley replacement without reshingling complete roof

As lead is so expensive, many roofing companies will also offer a fibreglass GRP closed valley alternative which can be neater and is less inclined to clog up

Mastercarpentry
Re: Roof Valley replacement without reshingling complete roof

Woven or cut valleys are the way it's done here, never is valley flashing left exposed on a shingle roof- that's a cheap shortcut way of doing the job. Patch the valley as explained but when it's time for the roof to be redone, have them install wide flashing on the decking first, then felt, then aluminum flashing, then felt, then valley roll roofing Ice and water shield works nicely here). Use a cut or woven pattern to shingle the valley, keep the nails away, and it will never leak thereafter unless it's damaged.

Phil

llmotoll
Re: Roof Valley replacement without reshingling complete roof
dj1 wrote:

5 year old roof is almost like new.

The normal valley installation follows a sequence like this:
1. 36" wide 30 lb tar paper.
2. Sheet metal, 24" wide. No nailing 9"-10" from the center out.
3. 30 lb tar paper.
4. shingles, no nailing 9" from center out. over a bead of lap cement along the edges of the sheet metal.

If your roof was done like this, you see how difficult it would be to extract the sheet metal valley without tearing up the tar paper on top of it.

You can sand the rusty spots away then paint with rust proof paint or cover the spot with tar and paint the valley, without over spraying the shingles..

Dude that is the most ridiculous assembly for a valley in a shingle roof I have ever seen. Does not even come close to industry standards set by the NRCA available on line to the public. You need to stop making recommendations on roofing immediately. based on that reply.... You do not have a single clue what you are talking about when it comes to roofing.

I'm sorry that assembly would work perfectly fine in a drought.

llmotoll
Re: Roof Valley replacement without reshingling complete roof
keith3267 wrote:

I agree with painting the valley before it starts to leak. If the flashing is galvanized steel, then I would suggest the following. Clean the whole valley with a degreaser and let dry completely. Sand to bare metal only where there is rust. Do not damage any protective coating that is still working. Treat the bare metal with a phosphoric acid product like Por15 rust converter. This makes an Iron Phosphide coating that is very effective in preventing future rust. Dry the area with a heat gun or hair blow drier. As soon as it is dry, use a zinc rich primer like a Zinc Chromate on the repaired areas. Then coat the whole valley with a primer and follow with a coat of paint to match the shingles.

If you accidently sand a hole in the flashing, complete the steps through the zinc chromate. Then use a metal filler like JB Weld to fill the hole. Then prime and paint.

Edit: use a spray can for the zinc chromate, but a brush and/or roller and tray are OK for the final coat of primer and paint. You can work a little paint under the edges of the shingles with a brush.

+1

Just paint the valley if it looks bad.

As long as the shingles are flexible the valley detail can be replaced. Pending the linear footage of valley to be replaced it may not be an economical option in lieu of full roof replacement

A. Spruce
Re: Roof Valley replacement without reshingling complete roof
llmotoll wrote:

industry standards set by the NRCA available on line to the public.

Got a link, the NRCA site doesn't indicate that this is available to the public, only members of the site/association.

dj1
Re: Roof Valley replacement without reshingling complete roof
llmotoll wrote:

Dude that is the most ridiculous assembly for a valley in a shingle roof I have ever seen. Does not even come close to industry standards set by the NRCA available on line to the public. You need to stop making recommendations on roofing immediately. based on that reply.... You do not have a single clue what you are talking about when it comes to roofing.

I'm sorry that assembly would work perfectly fine in a drought.

First of all, your comment is completely out of place, even if you disagree with this sequence, which has been the sequence around here for at least as long as I've been in business. This is not the first time you are coming out swinging and bashing others on this site. Is it "Your way or the highway" no matter where the roof is located? Well it wouldn't be on one of my jobs.

Second, drought or not, we get rain. We may not get as much rain as your city, but we do get rain - it's raining right now. None of the many roofs that I have ever installed since 1976 has ever leaked in our rains, ever.

John Oosterling
Re: Roof Valley replacement without reshingling complete roof
dj1 wrote:

1. What do you have in your valley? sheet metal or tar membrane?

2. If it's sheet metal, what exactly is wrong with it? Do you have a leak or it's just the appearance that you don't like? Do you have nail holes or rust holes?

3. What type of shingles do you have? How old is the roof?

Sheet metal, no holes but rust and don't want to take chance on becoming holes and leaking, want to repair before it does turn into holes and leaks, shingles are only about 5 yrs. old.

dj1
Re: Roof Valley replacement without reshingling complete roof
John Oosterling wrote:

Sheet metal, no holes but rust and don't want to take chance on becoming holes and leaking, want to repair before it does turn into holes and leaks, shingles are only about 5 yrs. old.

First, remove the rust (sand it or use a metal brush but don't force it), clean well.
Paint the valley with rust proof paint. If you spray, cover the shingles from the over spray.

keith3267
Re: Roof Valley replacement without reshingling complete roof

If you don't mind a little ugly, there is a roof mastic that is primarily used on trailers that you could paint over the metal with. It is thick and forms a membrane so if there are any holes in the metal flashing, it will fill them and stop any leaks. The stuff is difficult to put down so that it doesn't look like it was done with a broom, thats the ugly part. I would only recommend this if you were within a couple of years of replacing the roof, but since you are not, I am only giving information, not a recommendation.

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