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Small Cabin Forum / Cabin Construction / Metal roof screws leaking
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gauman2
Member
# Posted: 12 May 2018 10:35
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I have one screw leaking on my porch metal roof. While this is an easy fix by replacing with a new screw and washer. My concern now is that my cabin roof could have the same issue. The ceiling in the cabin is six inch spray foam so a leak would not be as noticible if ever if it was a small leak. What would you do for peace of mind?
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Mike 870
Member
# Posted: 12 May 2018 10:40
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I'd get up there and do a visual inspection of the screws and try to find any where the rubber washer is either over or under compressed. I just did a metal roof on my place and have the same worry.

ICC
Member
# Posted: 12 May 2018 11:49
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A screw that is too tight is the most common cause.

There are metal roofing screws that have a cup washer instead of the traditional flat washer against the neoprene. The cup prevents overtightening. Maybe too late now but something to remember.

DaveBell
Member
# Posted: 12 May 2018 14:03
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Ditto. Per the manufacturer, never tighten the screw so the washer is beyond the cup. How long ago were screws installed?

Borrego
Member
# Posted: 12 May 2018 15:58
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Too late now too worry about over-tightening (until next time anyway)...I would get up there with some roofing silicone and neatly put a little around each screw head......

Malamute
Member
# Posted: 12 May 2018 20:45
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I dont care for silicone in any way thats exposed to weather (or really for much of anything), its really a poor adhesive sealant and simply rubs off most things Ive seen it used on. Id use Big Stretch or other premium grade sealant.

Id also back the screw out a bit and squirt a little sealant under the washer, then carefully re-torque rather than try to put something on the head, which may not be the path the moisture is getting in.

Did you use the correct screws for the type of roof sheathing? For the metal Ive used, they spec'ed the smaller screws with 1/4" heads for real wood and plywood sheathing, and the larger, I believe they called them type S screws, for OSB. The small screws dont bite well in OSB, the larger screws are probably not spec'ed on wood and plywood because of cracking concerns.

gauman2
Member
# Posted: 12 May 2018 20:55
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The roof was probably installed 20 years ago by a previous owner.

KinAlberta
Member
# Posted: 12 May 2018 22:15
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Maybe your porch roof flexed and that caused the leak. Has anybody been walking across it?

gauman2
Member
# Posted: 13 May 2018 06:41
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Never thought about it flexing. I have been on it and the snow loads this winter.

old greybeard
Member
# Posted: 13 May 2018 10:33
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Mine was leaking at places after 20 years. Went up and snugged every screw, about 10% loose. Found a couple dozen which were rusted or stripped. Replaced them and sealed with rtv sealant. Dry now.
Doing the roof again I'd do standing seam.

toyota_mdt_tech
Member
# Posted: 13 May 2018 23:26
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Quoting: Malamute
I dont care for silicone in any way thats exposed to weather (or really for much of anything), its really a poor adhesive sealant and simply rubs off most things Ive seen it used on


I'd use a butyl type tape under the screw if it has leaked already. Under tightening and over tightening are common failures. The MFG is very specific on this.

DaveBell
Member
# Posted: 14 May 2018 01:32
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Quoting: gauman2
The roof was probably installed 20 years ago by a previous owner.

If the washers have rotted, water may have rusted the screws. After 20 years, time to replace them. (life span is 15-25) Silicone, rtv sealnt, etc. won't help keep the roof on.

KinAlberta
Member
# Posted: 1 Jul 2018 11:15 - Edited by: KinAlberta
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Quoting: DaveBell
If the washers have rotted, water may have rusted the screws. After 20 years, time to replace them. (life span is 15-25)

I’ve never heard of that as being a maintenance requirement. Unscrewing and replacing hundreds of screws is a big costly job. That changes the whole economics of using metal roofing.

Plus, replacing screws introduces a broad new issue - putting screws in existing holes. Same sized screw threads will likily strip the wood and metal and not seat as well as the first spin in. So would a larger screw with a larger washer be required when replacing any old screw or would a sealant have to be squirted into each hole but making sure none squeezes out and affects the proper neoprene washer-to-metal seal?



neoprene washer | Ask The Experts Forum | Metal Roofing Alliance
Guest User
2/1/2009
We are fixing to get a new metal roof on our house I was told that the washers will go bad and leak in 7-10 yrs. We heard that metal roofs should out last any shingle roofs.

https://www.metalroofing.com/spirit/topic/3742/neoprene-washer/



Borrego
Member
# Posted: 1 Jul 2018 11:34
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Quoting: KinAlberta
I’ve never heard of that as being a maintenance requirement. Unscrewing and replacing hundreds of screws is a big costly job. That changes the whole economics of using metal roofing.

Ain't that the truth? Hard to walk on a lot of metal roofs, particularly corrugated where you screw it in one panel at a time as you go...no walking on those...

DaveBell
Member
# Posted: 1 Jul 2018 11:36
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Quoting: KinAlberta
I’ve never heard of that as being a maintenance requirement.

Look it up.

Quoting: KinAlberta
Unscrewing and replacing hundreds of screws is a big costly job. That changes the whole economics of using metal roofing.

A handyman would probably do it for $500-$700. And then you are good for another 20 years.
A new roof averages $7,000.
What economic class did you take?

KinAlberta
Member
# Posted: 1 Jul 2018 11:51 - Edited by: KinAlberta
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I spent several hours reading metal roofing threads trying to confirm that over asphalt shingle applications was ok. I just couldn’t believe it could be ok. Well, it sure seems that it is ok and I now can perceive several benefits over firring strips:

1 - over-shingle applications mean there small touch points of support all over the surface of the roof (so walking on it can’t flex it very much at all),

2 - the grit provides airspace even at contact areas,

3 - old asphalt shingles still provide another membrane to shed any leaking water,

4 - the lapped asphalt shingles to provide one or two thicknesses below grade seal for the screws,

5 - the tar paper or other membrane under the old shingles is even one more layer of protection from leakages.

Laying gritty roll roofing vertically over a traditional horizontal lapped layer of tar paper over bare sheathing might even be an alternative to the 1”x4” firring.

However I don’t know what happens to old shingles over decades when ‘trapped’ between layers.

I also don’t know how much or how little air is needed to move under the metal to keep the underside good. 1x4” strips would allow lots of air to move horizontally but not vertically (the natural direction of air due to heat convection) so it may not be all that effective either.

I always thought that that dimpled tile and engineered wood underlay, either rolls out vertically down the roof or horizontally if lapped might be a good membrane over roof sheathing.

KinAlberta
Member
# Posted: 1 Jul 2018 18:44 - Edited by: KinAlberta
Reply 


Quoting: DaveBell
Quoting: KinAlberta
I’ve never heard of that as being a maintenance requirement.

Look it up.

Quoting: KinAlberta
Unscrewing and replacing hundreds of screws is a big costly job. That changes the whole economics of using metal roofing.

A handyman would probably do it for $500-$700. And then you are good for another 20 years.
A new roof averages $7,000.
What economic class did you take?


Yeah you’re right. I just googled the cost of the screws and they are really cheap. I thought they were a lot more. (When I ordered the metal for a couple roofs at the lake I just handed over the credit card without looking at the itemized costs.) The whole job including labour was maybe $2-2.5/sqft. on 1,700 sqft or so. Paid more for the materials than asphalt but then saved on the labour. And like you say, now have added a lot of potential longevity.

toyota_mdt_tech
Member
# Posted: 1 Jul 2018 20:27
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I found metal roofs hard to do if it has any pitch. My cabin is a 7.5/12 and my container roof is a 5/12, and the 5/12 was impossible to stand on without being tied off, very slick. A special built or modified latter would be idea. I am thinking a right angle bracket at the top with small rubber wheels, roll ladder up roof on wheels, then it flops over the ridge, lays flat on roof, but use felt tape on taller edge that contacts roof. Climb up to ridge and check fasteners along the way. You do not want to walk on roof without special bootie covers, special shoes. Any scratches of finish leads to rust.

KinAlberta
Member
# Posted: 1 Jul 2018 23:49 - Edited by: KinAlberta
Reply 


Seems that not only the screws with neoprene washers may need to be replaced but the entire metal roof. Too bad. I was under the impression that all the components; the neoprene washers, the screws and the metal would all last 40+ years, not just 20 years. Similarly when I’d mentioned that we’d installed 50 year shingles on our house someone said that long before then the sheathing would fail so the long life asphalt shingles were a waste of money. (Oddly our cabin with 1950s plywood was still like new in the 1990s but maybe our decades newer home has different plywood.)




The Truth About Exposed Fastener Metal Roofing - American Metal Roofs
Excerpt:

“...

All of these compromises in the quality of materials make these products 20-25 year solutions while most homeowners expect a new metal roof to last 50+ years.

And then there are all of the fastener holes. An exposed fastener system on an average sized roof will result in hundreds, if not thousands, of screws drilled through the face of the panels. These screws have rubber washers or grommets initially but those soon dry out and crack. Additionally, the screws do not allow for the metal’s expansion and contraction and the fastener holes slowly “wallow out” over time. Water eventually penetrates these growing holes and significantly compromises the integrity of the roofing system. In order to prevent water from penetrating, the screws will need to be replaced every so often with screws of a larger diameter.

When homeowners ask me about these products, I tell them that they must be aware of these shortcomings and decide if it is the right investment based upon their own goals and circumstances. These products have significant shortcomings that can detract from the value of their home and not last much longer than traditional asphalt shingles. ...”

- Todd Miller

https://www.americanmetalroofs.com/2013/06/05/the-truth-about-exposed-fastener-metal- roofing/




Plus checking the tightness of a hundreds or thousand screws bi-annually.




The Lowdown on Exposed Fastener Metal Roofing

Excerpt:
Going the cheapest route can cause your roof to have a lifespan closer to 20 or 25 years, rather than the 40 or 50 years most homeowners hope for.
Use best practices when installing the screws. While it's true that installation is relatively easy, that doesn't mean the job can be done haphazardly. Pay careful attention to the manufacturer's instructions. Only use the recommended screw gun for the job and be careful to create a tight seal, without using excessive pressure. Read, Metal Building Fasteners: A Quick Rundown for more detailed tips and recommendations.
Perform bi-annual inspections. While the fasteners may be exposed, it requires regular inspections to ensure they're performing properly. Make a ritual of bi-annual inspections of the fasteners - more frequent if you live in an area with more serious weather. Tighten any screws that have loosened as a result of weathering and/or temperature-related roof expansion and contraction. Replace any screws and/or seals that look ...”

https://www.whirlwindsteel.com/blog/bid/407560/the-lowdown-on-exposed-fastener-metal- roofing



DaveBell
Member
# Posted: 2 Jul 2018 04:03 - Edited by: DaveBell
Reply 


Metal roofing screws are available from 1" to 3 1/2". If you start your initial metal roof with 1" or 1 1/2" in the valleys, you could replace them every 20 years with longer screws that reach into solid wood. Thereby getting 40+ years of life from your metal roof.

If the metal panels ever need to be replaced then you can seal the old screw holes and use new course lines across the roof because you remembered to mark the old course lines on the roof edge and then chalk-line the new course.

(Adding a dab of silicone in the hole might help also but only if the screw gets into fresh wood. I don't think silicone as a thread restorer would provide the strength compared to longer screws in fresh wood.)

The Galvalume hot dipped metal roofing panels at Home Stores are the best for rain water harvesting. Asphalt being the worst, and Zinc/Galvanized the second worst.

https://www.sciencedaily.com/releases/2011/03/110307142229.htm

I've been researching the use of concrete backer board (about 4 PSF dead load) and rubber roof coating as a roof. You apply one color first coat, 24 hours later the final coat in a different color. Over the years if you see the undercoat appear, you just "paint" the roof again. I'm still looking into the viability of the rubber roof coating for rain water harvesting.

NorthRick
Member
# Posted: 3 Jul 2018 16:12
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Quoting: KinAlberta
Similarly when I’d mentioned that we’d installed 50 year shingles on our house someone said that long before then the sheathing would fail so the long life asphalt shingles were a waste of money.



Completely disagree with that. If the shingles were applied properly, and replaced before degrading to the point where they were leaking, your sheathing should last indefinitely.

I replaced the shingles on our house when it was 40 years old and the sheathing was fine. It's now 48 years old and I'm not the slightest bit worried that the sheathing will fail in 2 years.

Borrego
Member
# Posted: 3 Jul 2018 17:45
Reply 


Quoting: NorthRick
Completely disagree with that.


Absolutely! I've worked on plenty of 100+ yr old homes that have had asphalt shingle roofs...if properly maintained/replaced, the ply underneath will last a long time....
of course the plywood must be installed over the 1x's the first time it's done over...

Borrego
Member
# Posted: 3 Jul 2018 17:59
Reply 


Quoting: DaveBell
I've been researching the use of concrete backer board (about 4 PSF dead load) and rubber roof coating as a roof.


Out in the desert, we do a similar thing...I was introduced to this by some of the old-timers out there, everyone uses it even on high pitched roofs. It's worked out great for us so far...

We put down a basic rolled roof product and then wait one year to let it really bake in the heat. After the first year, we put on an elastomeric coating (Home Depot $120/5 gallons), 2 coats...repeat the next year, then every few years as needed...

It produces a slick, hard, reflective surface, much like plastic, but not slippery. After I did my cabin like this, I used it on a flat roof deck so I could have a walkable deck surface that was easy to install ala rolled roofing. Works great.

I personally think metal roofing is overpriced and a PITA because of the reasons mentioned above. But not everyone would want rolled roofing with a white coating on it at their nice suburban home....for an off-grid cabin like we all have, I think it's perfect though...

DaveBell
Member
# Posted: 4 Jul 2018 02:43
Reply 


Quoting: DaveBell
I'm still looking into the viability of the rubber roof coating for rain water harvesting.


The MSDS for EPDM Rubber Roofing Roll (contains Carbon Black) and EPDM elastomeric coatings indicates they are not a good candidate for Rain Water Harvesting.

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