Thoughts on metal roofing.

Dave Shepard · September 30, 2020, 08:51:58 PM

My only experience with metal roofing has been on steep single pitch roofs. I'm designing a small barn with a lean-to on one side. The main roof will be either a 9/12 or 12/12. The lean-to will be fairly flat, probably around 4/12. I'm wondering what the limits of metal roofing are regarding low pitches. Also, I'm wondering if it's best to have the lean-to come in under the eaves of the main roof, or to have a transition from steep to flat section of the roof. Thanks.

Brian_Weekley · September 30, 2020, 09:36:32 PM

Hi Dave—here's the installation guide for the 5V metal roof that I put on my barn. It says the minimum slope is 3/12 in this guide (check out the slope change detail diagram on the last page). The slope of my shed roof was 25 degrees (5.6/12) and I just used a direct transition.

https://www.abcmetalroofing.com/Documents/5V-Crimp-Manual/

Brian

Don P · September 30, 2020, 09:40:53 PM

The manufacturer's literature will state min pitch for the particular type of metal roofing, usually quite low pitches, all will do 4/12.
Transition is easier and better IMO, no snow stacking against a fascia.
I just today moved the scaffolds and ladders off a roofing job from last week 10/12 and a transition onto a 4/12 porch. They had 2.7" of rain yesterday so we had a good check on it right off the bat. That is my last roof

I hope :D

Dave Shepard · September 30, 2020, 09:55:44 PM

Thank you Brian and Don. Very helpful.

Tom King · October 01, 2020, 09:21:26 AM

I've done standing seam on pitches as low as 2 in 12, on sheds, and porches, with no problems. One is even about 1 in 12. I reframed the old structure of that 1 in 12 roof, to make sure the planes were perfectly flat, and used the heaviest gauge of metal. It's worked fine.

I won't put an exposed fastener roof on anything again. I get calls to troubleshoot leaking metal roofs, more than I want, but I do end up going a lot because I'm usually the person of last resort. I've probably seen most of the problems. We may have the only chicken coop with standing seam roof.

Tom King · October 01, 2020, 09:46:25 AM

I found a picture of the 1850 house we redid, with the 1 in 12 porch hip roof. There's one exactly like it on the back of the house too. Originally had lead sheets on them, but the framing had sagged enough that they held water.

picture later.

sawguy21 · October 01, 2020, 11:10:58 AM

I had a metal roof over my mobile home, it caused me grief. Sliding snow kept taking the stack off and I wasn't going up there to shovel. Never again! Like Tom I have seen too many problems with exposed fasteners.

kantuckid · October 01, 2020, 01:46:45 PM

I'll share this: We/I started in May 2019 to find a supplier and installer for a standing seam roof. I'm very rural and unless you are near a city it's tough to go that direction as most local roofers won't ouch standing seam meta as they lack experience and also seem to shy away simply because it goes up slower. Within logical distance I have 5 different brands of metal roofing to choose from, one a mfg. Finding an installer was a much different challenge. The Amish brothers/partners I found turned out to be younger brothers of the man who did my last shingle roof yet since they don't advertise too much I'd missed asking them. In the new England I suspect the population supports more pricey roofs jobs but here and rural a school or library is about all that gets them and then since the taxpayers are footing the bill the all types larger roofing companies can afford to bid and do that style of roof.
In the end I'm glad I persevered and didn't settle for an exposed fastner roof! In fact I paid little more for labor and materials than several of the cheaper metal bids I got.
I did change my 1st choice of suppliers to be in agreement with my contractor as he preferred the local mfg who would run materials if something turned out wrong, missing etc., so no job hitches.
Most local home builders hire out all types of metal to aa roofer and many of those have never done even one standing seam roof.
I went with 24ga metal and every few minutes it sounds like incoming as our big buckeye tree drops on the new roof-sounds like "incoming"...
My current off grid cabin will get an exposed screws roof done by yours truly.

kantuckid · October 09, 2020, 08:59:12 AM

A metal roofing mfg difference I ran across was that "local roll formers" buy coils of pre-painted roofing steel. A mfg in PA, their engineer told me they heat form their metal THEN they coat.
Liken a vehicle mfg stamping a fender with the paint on it to stamping then the finish comes after the stamping press. Of course, rolling is not the same as stamping but I bought his argument that their finish is a better application timing wise in forming steel.
Most all seem to use the same Valspar paint products from my searches.

Dave Shepard · October 09, 2020, 05:03:02 PM

Today's question: my current ptoject is getting pine roofers put on. I don't know when it'll get the roof. Can I, or should I, put tar paper or ice and water shield on under the metal? I'd rather not rely on a tarp. Thanks.

Don P · October 09, 2020, 06:59:33 PM

Yes, you should. I've switched to the synthetic underlayments, titanium or WR Grace makes one, can't think of the name at the moment. They are more expensive but hold up to sun and wind better that tarpaper. Prior to that we would usually lath strip the paper, string it if in high wind and still on one house I went up 7 times to repair or redo the paper before we were ready to put the roofing on, major time suck. Ice and water is not a bad idea if you are pushing the minimum on pitch.

Texas Ranger · October 09, 2020, 07:49:04 PM

Great, until they start leaking. 30 x 130 metal roof that does not like winds, like Ike, etc.

kantuckid · October 10, 2020, 07:43:02 AM

My local metal roofing mfg sells a roll material, on display in their showroom, that's designed for roof as an underlayment on new jobs not over shingles as my home had already.
In general appearance it looks just like common house wrap to my eyes other than no brand names printed all over it, it light colored on one side and dark gray on the other.

I assume term "roofers" means 1x4 lumber, or similar?

Just saw a man with a blue tarp on his roof from the LA storm 6 weeks back and still on there.
I do see those used as a temp thing by roofing companies when weather catches them on a job.

I do feel that exposed fastener metal roofs have their place. An e.g. is agricultural roofs like equipment sheds and such. Also, in my area, what with many low incomes among those who also happen to own their own homes, they are an important roof choice for people who simply cannot afford any other choices. Well installed they do function. My own shop roof is getting a galvalume roof soon, not something I want on my home it will easily last far beyond my time.

Don P · October 10, 2020, 08:37:28 AM

There still tatters of them on some roofs here from years ago but they do work short term.

One thing, I haven't used Ice and water under metal and thinking more I'd ask the manufacturer, certainly don't use the mineral coat stuff but even so they might want a slip sheet of something like rosin paper between the two if you go that route. We had one of the pro roofing companies come out and do site formed standing seam on a roof. I had it in tarpaper but they rolled rosin paper vertically under each pan as they worked to act as a slip sheet under the metal.

As I talked to them they had recently done the capitol building in WV. It has gold leaf applied over the roofing metal. Super thin, glued down and worked with soft bristle brushes, steep, way off the ground. The first attempt didn't work so they had to do it twice and they were searched daily to make sure no one was carrying any home. No thanks! :D

kantuckid · October 10, 2020, 10:11:59 AM

I've always wondered if it was "fools gold" or real stuff? Is it CO that has a gold roof too?
Side entertainment: In Topeka, KS when we lived on bicycles and went into everywhere and I mean EVERYWHERE!, we went up into the dome all the time via suspended cast iron steps and could look out over our one main drag capital city. Of course nobody can do that now as the lawyers are protecting the public now. Another favorite thrill spot was the pipelines hanging under the blvd Kaw River bridge or the Union Pacific rail bridge, etc..
Yes, I think the material I mentioned is a slip surface for metal contraction/expansions. On my own roof the mfg said not needed as it can move on the 1x 4's OK.

Tom King · October 10, 2020, 02:03:03 PM

The synthetic underlayment has much better traction for feet, too. It seems like it wouldn't but it does. It's worth the price difference alone, just in the weight difference of getting it on the roof, and dealing with it while you're up there.

When I install standing seam, I don't put any fasteners in the underlayment. We roll it down from the top, and just let the sheets of metal hold it in place. Fasteners underneath the metal can telegraph through, and show on the surface.

As far as coating the metal before it's formed, I thought that's the way it's all done. In any case, it's fine, and will hold up for the guaranteed life. It's not merely a normal kind of paint. That on my barn is now 40 years old, which was the guaranteed life, and it still looks just fine.

kantuckid · October 10, 2020, 02:26:26 PM

FWIW, I drive past many metal roofs on homes which are seriously UV faded, age unknown of course. Green & red seem to be the worst.
I priced one of those baked on finish steel shingle roofs back when they came out. The materials alone cost more than my home.

mike_belben · October 10, 2020, 03:11:15 PM

Metal is king in tennessee. Standing seam not as common as 5v which took the crown from ruffled potato chip sheets some time ago. When it leaks we get a mop and a $60 pail of silver goo to slather on. Theres still old barns with straight sheet metal here and there but not usually looking too good.

Big issue to keep in mind is under certain conditions metal roofs condensate and sweat on the underside like crazy. Itll look like the only place it rained was INSIDE.

Tom King · October 10, 2020, 03:19:01 PM

Quote from: kantuckid on October 10, 2020, 02:26:26 PM
FWIW, I drive past many metal roofs on homes which are seriously UV faded, age unknown of course. Green & red seem to be the worst.
I priced one of those baked on finish steel shingle roofs back when they came out. The materials alone cost more than my home.

I've never seen a dark color that didn't fade, and some very quickly. The blues are pretty bad too.
Our Barn roof is Lightstone (a light yellowish, tan), and it's dulled out some, but the 40 year old color still doesn't look bad from any distance. At least it's still all intact, with no rust.

Bruno of NH · October 11, 2020, 02:40:21 PM

I was told never put standing seam roofing over ice and water shield without a slip sheet on top.

sprucebunny · October 11, 2020, 03:30:40 PM

I'm buying a new-to-me house that needs a roof. After 40 years of steel roof ownership w/exposed fasteners, I'm getting it again. Also have a second building w/20 year old metal.

They make special High Temp Ice and Water shield for use under metal and synthetic underlayment that has a high temp rating. Check. I also bought lots of butyl tape which withstands high temp. I plan on sticking either the butyl tape or some small pieces of the ice and water shield to the backs of the site pre drilled sheets where the holes are so even if the stickum doesn't stop the screws from working out, it should stiffle any leaks.

I'll let you know in a month or so if it was a giant pain :D

Brad_bb · October 12, 2020, 09:01:47 PM

I'm sure there are some manufacturers with poor finishes, and others with great ones. All of my buildings have gotten standing seam Metal. They come with the coils of material and roll it on site. One thing to keep in mind is that snow can slip easier on the steel roof. For where I live this has necessitated snow guards to keep big bunches of snow from sliding in hitting someone. All of my roofs also incorporate a cold roof. For example on a SIP roof, titanium UTL synthetic paper is applied to the sip, And then a 2x grid that access both a cold roof and an electrical chase. A cold roof will allow the roof to breathe and any moisture to come out. It's also an extra layer of insulation between the sheet-metal and the sip. A cold roof will allow the roof to breathe and any moisture to come out. It's also an extra layer of insulation between the sheet-metal and the sip. We do the same thing on other roofs as well. Create a 2x grid as a cold roof.

Conduit is run on the roof for pendant lighting, and to get from one side of the roof to the other. I wouldn't run the electrical on the roof if not in conduit for safety.

In this last pic you can see the sip, Then walk boards are applied, then removed as titanium UDL synthetic paper is applied, and then a walk board goes on that(this also becomes part of the grid.)

kantuckid · October 13, 2020, 07:53:56 AM

My metal material came in sturdy crates with truss sides, standing on edge- unlike stacked exposed fastner metal roofing. The factory I bought from is in Winchester, KY 35k away, but they have locations in IL and OH as well.
Fact is they leave the crates (Amish have no way to remove them anyway) and tightwad me took them apart for the nice #1, 2 x 4's. I now have a collection of hundreds ranging from 3-4' to 14'plus.
All the mfg's I searched used Valspar coatings made for roofing.
I think many of the smaller players in the coating industry are gone? Probably couldn't do the EPA stuff? My home has 32 gallons of poly inside that came from one of those local paint companies back when but now gone.