Standing seam roofing for 2:12 without mechanical seams?

[pago cruiser]

(Finally) building a 40W x 24D (or26) x 13H garage. Criminy, I have been working on this for years...
Roof will be 12" parapets on 3 sides, with water sheeting off the back.
Cannot seem to find a metal standing seam roof that is certified at less than 3/12 without resorting to mechanical seams. Nothing in R-Panels either.
Would prefer to do this at 2:12, otherwise the building gets 2 feet taller...
My local plan checker has indicated that I must have min 3/12 on my plans, unless I can show him the manfg certifies it at less.
TIA.

 

[readhead]

You should consider a rubber roof. If you go with a water proof SSR roof at that slope you will have to pay for the inspection and warranty from the manufacturer.

 

[jack stand]

^^ this is what I was thinking at that low pitch and not visible from 3 sides.

 

[billconner]

Curious when you say "rubber" if you think epdm or pvc or tpo?

Like Pickle's garage...

 

[Voi]

Bridger Steel based out of Montana has an exposed fastener, structural steel that is rated down to 1:12.

I think it's their 7.2 Structural Steel.

 

[jack stand]

I'd think that it would have to include a sealant (rope caulk?) of some kind at the long panel overlap seam. Maybe they have a much "taller" rib @ the overlap?
I haven't used much of the snap down standing seam, but would think that it would be much more water resistant than a simple screw down "agriculture" panel that generally has a 3/12 minimum pitch.???

 

[sjvicker]

I looked into this awhile back and couldn't find anything less than 3/12 for snap lock standing seam.

 

[jrsavoie]

I found some that would work on a 2-7/16/12 pitch roof.

McElroy in Clinton, Illinois

 

[K'ledgeBldr]

Go TPO.

 

[scofo]

I know you were primarily interested in standing seam but Mueller Metals claims their R panel is good to 1/2:12. Their standing seam with mechanical crimp is good to 1/2:12 also
I have R panel at 2.5:12 on my house. No issues in 13yrs.

 

[jrsavoie]

Go TPO.

What is TPO?

 

[billconner]

thermoplastic polyolefin

It's a single ply membrane roof. Usually white compared to EPDM which is usually black.

 

[ducatithunder]

I have a mono pitch roof that is 1/12 pitch. Im located in MD so I get snow and ice loads. I did a snap lok system for the standing seam. I have the entire roof sheathing covered with WIP I/W shield. I have no issue with water sheeting off the back of my roof nor do I have issues with snow load. We got 2 feet of snow a couple months ago, again no issues. IT took about 4 days to finally melt and sheet off.

The company that did my roof had no issue with a snap lock on a low pitch roof. I can send you the details if you like. They came in and rolled out the panels out on site. Each panel was roughly 34ft long.

My garage is very visible from the road above so I didnt like the idea of a membrane. For the extra cost ... maybe 6K I ended up with what you see.

 

[bob15]

Use Etrabond double sided tape between the roof panels and it won't leak.

https://www.hbfuller.com/en/north-a...ds/eternabond/eternabond-roofing-repair-tapes

 

[theoldwizard1]

thermoplastic polyolefin

It's a single ply membrane roof. Usually white compared to EPDM which is usually black.

Some flat roofers consider it superior to EPDM. Any roof penetrations should use pre-molded inside/outside curbs. These are heat welded/bonded to the roof. No glue or caulk is required on the outside.

Both TPO and EPDM come in different thicknesses. I have heard that TPO holds up better to ultraviolet (sun light).

 

[oldmxracer]

Save Yourself some grief, it sounds like the roof will not be very visual, just put a membrane roof on it, EPDM glue down can be a diy roof with a little study. I have many years of roofing under My belt. Just My opinion!

 

[rcbk00]

My roof is 2.25/12 and I used a snap lock panel. I covered the whole roof with ice and water shield first, just to be safe. The panels were made by a local contractor with a roll former on a trailer. If my memory is correct, the manufacturer of the roll former said the panels were approved down to 3/12, but when my installer called them about my roof, they said it would be fine. It's been 10 years and I haven't had any problems.

 

[pago cruiser]

Thanks for the info all. Good to see there are several choices. Been kind busy at work and my design has also changed a bit.
I now need 1:12 in order to provide max headroom at the back. This will give me 9' min for storage racks above the car hoods.

I ended up (I think) with a standing seam with mechanical seams. Good reference here if anyone else is so inclined:

Low Slope Metal Roof: Which Panels Are Best For A Low Pitch?

Wondering what type of metal roof is best for a low slope roof? We go over the best types of metal panels to use with a low pitch roof.

www.westernstatesmetalroofing.com

They would not certify the Snap Lock at less than 2:12.
I was not thrilled about fasteners in the water channel of their 7.2 or their R Panels. Seems... problematic.
The Mech Seamed is certified down to 0.5:12! Single or double lock options, both about $3.75/SF for 24g, and $4.55/SF for 22g material.

The only drawback is the roofing vendor does not provide, rent, or sell the seamer! Nor does anyone in AZ (I'm in the Tucson area)! That said, they provide a link on their site, which takes you to a seamer rental company in... would you believe Mississippi? Called them, and they charge $50/day rental, starting from when I sign for the delivery, until it is returned to them via Fed X. They indicated that 1000 SF could be done in one day; so 1 day of working and 2 days shipping will cost me another $300.

Seems an interesting way to do business... sigh.

 

[RoninB4]

Following this for my parking area design. Dammit things are expensive now.

 

[Zippercat]

Did you try these guys?

Panel Seaming Archives

Find professional panel seaming tools for metal roofing projects. Create strong, reliable seams with precision tools made for durability.

www.stortz.com

 

[jack stand]

I'd check with a nearby "commercial" *roofer and see what he'd recommend. Generally it will be what is commonly used in your area on/with similar conditions and works well, is cost effective and it'll be what they're familiar with therefore they can bid it with complete confidence in they're labor and material estimate.
If you're stuck on the metal, from what you've described, I can't imagine the need for the heavier gauge material.
* flat or low pitched roof

 

[welder57]

Check with MBCI, Ultradek. They may or may not be able to supply you panels and clips. 103 Mph Wind Speed (Code) there may be the problem, Doublelok 24" 24 Ga. Seamed Panel would be the way to go.

 

[pago cruiser]

Thread resurrection time...
Finally got the garage under construction (now 36 x 26, the biggest I could fit on my hilltop), with concrete now scheduled for next week.
Found a local vendor who reps "Metal Sales" (nice germane name....) who makes a 1.75" rib height Snap-Lock system certified to 1:12 pitch (I am 2:12), that also meets Miami Dade County (MDC) for windspeed. MDC is the typical worst case design criteria nationwide for HVAC stuff (Louvers and rooftop fans) that I design (or did, before I retired ). Rated to -137 PSF! That would be (I think) suction trying to pull the roofing off as a hurricane rips through. That is also a pretty big number. In designing the footers for my adjacent wood stand-alone patio cover, the force generated by a 100-mph wind (nominal design speed for my hilltop) is about 50 PSF.

Another question: I am going to be using a product by "Grace" called "Ice and Water Shield HT" over the entire 5/8" ply roof deck. Probably overkill, but.... There are multiple roofing references discussing the benefit of a thermal break in the roofing; here in southern AZ in summertime a roof can reach 180F. While I don't want to spend the several thousands necessary for battens and rigid insulation, I might spend a grand on something like the attached "Rolled Roof Insulation Mat". While I think the idea technically makes sense, the Roofer I have engaged thinks it would be a waste of time. Don't know why, but it seems every Contractor on each discipline for this project (Concrete guy would not use dobies, or concrete pad covers, even though we are seeing mid 20's at night), Framing guy (does not want to install a 42" door), and now roofing, has no interest in doing a "better" job. Even if I am paying them for it!

It's too late now, but tomorrow I am going to call the "Metal Sales" folks, and see if I can reach somebody in engineering to get their thoughts.

Any thoughts on this 0.40" (before compression) "Insulation Mat" under the Standing Seam panels? I can't quite get my head around if each clip would need a 0.40" standoff, or if the 0.40" is compressed to (say) 0.10" at each clip...

TIA. Love this site.

 

[billconner]

it says "ventilation", not "insulation". What do you think you get from it? Certainly no insulation.

 

[pago cruiser]

With all respect, air at about R3.6/inch is a great insulator, almost equal to any typical insulation, excluding vacuum panels (at R60/inch) and Space Shuttle Heat Tiles (at R50/inch).

How great?:
Assuming I was to add 0.4" spacers to the clips (to not crush the Mat) I could prolly maintain the full thickness of the stuff, at 0.4". Call it R= 1.44 (0.4*3.6). As U=1/R, this equates to a U value of 0.69. Heat transfer = UADT. For simplicity make the area 1 SF, and the DT (180 - say, 70) = 110.

So without the Mat (and ignoring the wood R value, as it is the same in both cases for these calcs) I have heat transfer of 1*1*110 = 110 BTUH/SF. With the Mat I have 1*.69*110 = 76 BTUH. So I will have stopped (1-(76/110)) = 31% of the heat from reaching the garage space. I have measured 130F within my shed in August at about 6 ft above slab; reducing that heat flow by 31% is a big deal. Based upon my 936 SF, this cuts conduction from (110*936) 102,960 BTUH to (76*936) 71,136 BTUH. This 32,000 BTUH sensible saved is about the output of a 3- ton HVAC unit.

Are there technical or real-world problems with the mechanical aspects of the install? Wish I knew; hence, my post.

That said, after going down this rabbit hole, the cost of the Mat at $1/SF is about equal to a 2" polystyrene rigid foam, with a R value of 7.7. Think I'll look at the rigid insulation to get the most bang for the buck. But... this will also require 2" longer screws for the clips, and I'm not sure the rigid foam has enough compressive strength to mount the clips on without deforming ...hmmm.

New solution, new problems... Sigh.

 

[pago cruiser]

Figured I would close out this thread.
Got ahold of the Engineering Guys at Metal Sales yesterday. They do NOT have any factory approved method of adding insulation under their panels. As I suspected, they need the clips anchored to a solid surface. When I asked him about spacers under the clips, he said..." well that might work; but we do not sell the longer screws, and if the heights of any "extended" clips were as little as 1/16" off in elevation, that difference will be telegraphed to the panel". Meaning an oil-canning type of deflection in the flat surface of the panel.

The ONLY thing he could suggest is that I build and secure a say, 2" x 2" framework on top of my existing sheathing to "house" the 2" insulation panels, and then the metal roofing would be secured onto these frames. Sure; I'll build a second roof on top of my first roof...

So. If you want metal panels, at least there is a Snap Lock version that is high wind rated; but apparently none of them have an easy manner to install a sheet insulation product in between the roof sheathing and the metal panel.