Minimum Pitch for Metal Ribbed Roof

[LouNY]

My main concern would be ice damming in the winter, if the snow on your house roof melts and runs down to the steel roof and freezes.

 

[EddieWalker]

Here in East Texas, we don't build for snow, but do have to deal with extreme rain instead. Two weeks ago we received 3 inches in less then an hour and I was at 4 7/8s inches for the day. Slope of metal roofs has to be enough to shed a lot of water quickly. For metal, my local provider is Mueller's, and they told me that at 4:12, I don't need to worry about sealing the overlaps, but if I go less, I need to seal the overlap, but not to go less then 2:12

 

[lzicc]

Yeah, I ignore those type of post. I'm thinking the same way you are thinking. I'll also have gutter on the eave end to catch the water.

You'll have no load problems. Worse leak problem you might have is that water running off the eave may try to turn the edge of the tin and come back toward the house. If you give this roof an 1.5" of drop it'll be fine.

Don't worry about "The Sky Is Falling" crowd.

 

[RoyKing]

You don't have any good solutions.. You can't put enough drop because of the other window. If you make it fit rain will be all over soffit around the other window it will rot everything. If you want sun screen use a small rollup. But a enclosed screen room will be problem

 

[SandburRanch]

For low slopes the over lap was increased to compensate, but that was back in the good ole days.

 

[the old grind]

See posts #16-20 and carry on.

Rafter and slat spacing of 24" min should be enough. Similar sheds and lean-tos next door have handled mid-MI's snow for a decade w/o leaking. The steep one is ~1:12 pitch, if that.

IMO, ice damming isn't likely on an unheated surface below a 18" o'hang. (toss handful of rock salt up there if needs) Small o'all size & low placement should be easy to sweep of heavy snows, and snow spreads its weight evenly, nothing like someone walking up there.

If the sky didn't fall in too big of chunks, I'd like to sit under such to 'watch' storm clouds and birds.

 

[ovrszd]

If the sky didn't fall in too big of chunks, I'd like to sit under such to 'watch' storm clouds and birds.

Good point!!!!

 

[lzicc]

This is exactly how I am looking at it. There are a lot of lean too's that have hardly any pitch. As far ice damming, that won't be an issue since there will no heat to melt the snow on the roof. I think I'll be fine. It's nice to hear other inputs though.

See posts #16-20 and carry on.

Rafter and slat spacing of 24" min should be enough. Similar sheds and lean-tos next door have handled mid-MI's snow for a decade w/o leaking. The steep one is ~1:12 pitch, if that.

IMO, ice damming isn't likely on an unheated surface below a 18" o'hang. (toss handful of rock salt up there if needs) Small o'all size & low placement should be easy to sweep of heavy snows, and snow spreads its weight evenly, nothing like someone walking up there.

If the sky didn't fall in too big of chunks, I'd like to sit under such to 'watch' storm clouds and birds.

 

[Oldoak]

--------------------------------------------Don't worry about "The Sky Is Falling" crowd.

I don't think anyone here is shouting "The Sky is Falling". Just many varying opinions and suggestions.

Yeah, I ignore those type of post. I'm thinking the same way you are thinking. I'll also have gutter on the eave end to catch the water.

You also ignore what the manufacturer recommends. :confused3:

 

[QRTRHRS]

I'm doing a 6"/12' for a horse stall awning. I'm in N. TX, so snow load isn't typically an issue. I'll also tape the seams where the sheets overlap.

I agree on taping or caulking the overlap. I had 1/12 sheds added onto both sides of a sixty foot long barn with up to about 16 inches of wet heavy snow on it. Perhaps it was due to having animals within but after snow events like that I would get minor enough ice damming on the one foot overhang outside of the walls. Then during a melt, water would pour out of the seams.

In my location, a few inches of snow usually melts off quick enough but beyond that, I shoveled it off. Having the screws in the flat made it easy enough to shovel off with a plastic shovel and did not scratch the paint off of the tin.

 

[Diggin It]

You also ignore what the manufacturer recommends. :confused3:

Manufacturer recommendations are full of hidden lawyer speak. They're all about potential liability to the manufacturer. 'If you don't do it this way, you can't hold us accountable, yadda-dada, yadda-dada, yadda-dada......' It doesn't mean that is the ONLY way to do it. Humans regularly tweak those recommendations without incident. You can do it different and still be safe if you design for your particular application, which is what we're advising the OP based on our own experiences.

 

[/pine]

The OP says they will be using "ribbed style metal roof"...exactly what style? one of the most common is "5V"...
There are many different configurations especially for commercial / industrial applications...
One of the most common low pitch commercial roofs are seen on rental storage unit buildings...some have hardly any pitch at all yet but making sure rental client properties are kept dry would be paramount to a storage business...

Most of the roof systems that come with storage building roofing packages include ribbon calking and both hold down and stitch screws...

 

[RoyKing]

Snow load just use more framing and move slates closer. The problem is going to be where the roof meets the wall above window and soffit area. Rain is going to keep that soffit wet from splashing. They are not designed to get wet and debris will build up in that crevasse you create. Both soffits need to be non vented vinyl. Where the tin meets the vinyl siding the whole area above that valley behind vinyl needs to have water barrier and return splash to the tin roof. Also on bottom edge of the vinyl a notch will need to be cut to keep the water from traveling the length. Vinyl is far from water proof when rain isn't falling straight down. Plus I think the roof line will look terrible.

 

[lzicc]

You all bring up valid points. Here is how I am looking it. I can buy a gazebo or canopy and put it over the porch, but the gazebo's are expensive and the roof of the gazebo would slant in all 4 directions which when it rains, it would slant towards the door and the rain would hit the door. The canopy would more or less do the same thing, so my thoughts is that it would be more cost effective to built a slant roof. I could make it the size that I need and it would look nicer and be more stable. As RoyKing mentioned, wetness and debris could collect between the eave and the roof which is a good point, but I could use trim coil that is the same color of the gutters and flash it behind the gutter and slope towards the new roof. /Pine, the roof panels I am looking at are at Home Depot.

https://www.homedepot.com/p/Metal-Sales-8-ft-Classic-Rib-Steel-Roof-Panel-in-Charcoal-2313217/204254778

 

[Diggin It]

I recommend NOT buying them at any Big Box store where they can be $3.00 per linear foot or more.. Check roofing suppliers or lumberyards. Prices I just got are around $2.25 per linear foot. You can also get custom lengths that way, 8'6", 9' or whatever you want. Most don't stock any at all, but delivery is usually within 2-3 days.

 

[Lineman North Florida]

You should be fine doing what you want to do and as far as manufactures specs they also tell you not to fasten tin in the ridge but people have been doing it successfully for more than 50 years, leak free.

 

[dnw64]

ABC Metal Roofing makes a PBR profile that is rated to 1/2:12 pitch. The ribs are 1-1/4" tall and 12" OC. PBR | ABC

We are getting ready to replace the standard Imperial Rib (3:12 rated) panels on our 2.5:12 pitch shop roof.

 

[3Lfarms]

Tuftex translucent panel installation instructions specify a minimum of one inch rise per foot, or 3” per foot in heavy snow areas. At that low of a pitch, you do need to seal the overlaps to prevent leaks between the panels.

I covered my pergola 4 years ago with 16’ Tuftex panels installed at just over the 1” per foot minimum. It has held up great and has had 8” of snow several times with no problems and no leaks.
The wind is favorable here so water is never blown up the pitch of the roof, but in my installation, it wouldn’t matter if it did.

 

[ovrszd]

I don't think anyone here is shouting "The Sky is Falling". Just many varying opinions and suggestions.

You also ignore what the manufacturer recommends. :confused3:

And you are free to ignore what he does.

 

[aczlan]

I agree on taping or caulking the overlap. I had 1/12 sheds added onto both sides of a sixty foot long barn with up to about 16 inches of wet heavy snow on it. Perhaps it was due to having animals within but after snow events like that I would get minor enough ice damming on the one foot overhang outside of the walls. Then during a melt, water would pour out of the seams.

Yep, animals will put out a surprising amount of heat.

I recommend NOT buying them at any Big Box store where they can be $3.00 per linear foot or more.. Check roofing suppliers or lumberyards. Prices I just got are around $2.25 per linear foot. You can also get custom lengths that way, 8'6", 9' or whatever you want. Most don't stock any at all, but delivery is usually within 2-3 days.

I agree. Get them precut to the right length for the roof (no horizontal joints that way), put down silicone calk on the seams and make sure you flash it properly where it meets the wall/eave.

Aaron Z