Metal roof+metal chimney+snow=PROBLEMS
I built an airplane hangar for myself on a private airstrip in central New Hampshire a couple of years ago. About 48 x 48 footprint. Not quite finished yet, still a few details. I had planned to build a masonry chimney, but time and budget forced me to put up a metal chimney for the woodstove (too much money spent on red cedar shingles and the metal roof). I installed the chimney according to the Simpson Duratech and the Fabral instructions. Well, last winter we had a LOT of snow, and the chimney was damaged by the snow. I wasn’t there when it happened, so I am not sure if it was due to a snow avalanche or just snow build-up pressure on the chimney. I am looking for the best solution so this is less likely to happen in the future.
The roof is a click-lock type standing seam steel Fabral 1 ½ SSR with 16†pans, 24 ga. On a 6/12 Advantech deck. I have learned the hard way to avoid the avalanche line when there is snow up there. The roof of my pickup has a huge dent from a snow slide. I used the metal roof because my neighbor had his hangar collapse a couple of years ago after a series of snow-rain-snow-rain storms. Truss failure. Total loss of irreplaceable antique airplanes. I have 48′ clear span trusses.
http://www.fabral.com/product.php?id=19
The chimney is a Simpson Duravent Duraplus 6â€.
http://www.duravent.com/pdf/catalogs/duratech.pdff
It is installed with a Fabral-supplied metal roof jack:
http://www.pipebootexpress.com
The roof pans are about 30’ long, secured to the Advantech with screws at the peak, and with expansion slides every 18†down to the eave. The chimney penetrates the roof about 1/3 of the way up from the eave. The roof pans expand in the sun down from the peak, where it is screwed through, and seem to move a 1/4†or so at the eave drip edge.
I have considered four possible solutions for the chimney problem:
1. Use snow guards; there are many types out there. Most attach with screws through the metal to the deck. I am concerned about the differential movement of the metal and deck eventually causing leaks at this point. Fabral recommends a type that clamps on the raised seam without poking holes through the pan, but that doesn’t seem strong enough to me.
2. Build a pipe-type snow guard, with screwed-thru attachments through the raised seams, probably two pipes high, above the chimney and one pan on either side.
3. Use a Vent-saver
https://snoblox-snojax.com/shopping/product_details.php?id=8
Has the same concern about the screw-differential-movement leak problem as conventional snow guards
4. Build some type of cricket. I have some metal left over, but the same question-how to attach and prevent leaks. How high?
What do you think?
Replies
Can chimney path be re-routed internally to come out closer to the peak?
If it was sliding snow that did it, maybe some of those snow stoppers which are supposed to keep folks on the ground from getting dumped on?
Good idea. I did cheat the chimney over as far as I could toward the peak, but the inside of the building has to remain clear. And, with the shallow 6/12 roof, there is not a lot of room for elbows and offsets. It pretty much has to be where it ended up.Thanks
I really don't have an answer, just wanted to comment on a nice looking hanger.
Snow guards are the only thing I can think of.
Slateman has a source for good ones.
Edited 7/26/2008 11:24 am ET by frammer52
Stouter pipe or sleeve? more braces closer to the roof? Now you see this one-eyed midget
Shouting the word "NOW"
And you say, "For what reason?"
And he says, "How?"
And you say, "What does this mean?"
And he screams back, "You're a cow
Give me some milk
Or else go home"
Thanks Frammer. The most interesting thing about the building is the big hydraulic door which opens with two cylinders. It is about 40 x 12', hangs on 7 big hinges. Two hp motor opens it in about 60 seconds. It weighs about 4500 pounds. The pic shows it before I finished the shingling. With the vertical lines of the shingles, it is hard to see that there is a door there. When it is up, it is exactly horizontal. Up--lotta forces going on. I welded up a steel bar joist horizontally across the opening at the top to resist the outward forces at the hinge points.Down--the cylinders are double acting so they pull the big door into weatherstripping. It is surprisingly airtight.Dick
me likes! thanks for the picts.
We have used a sleave made from well casing. The boot goes around the casing. The casing is braced by the roof on the lower side and against the truss to counter the rotational force.
Interesting idea. How far above the roof did you go? If the boot goes on the pipe, did you also seal between the pipe and the chimney?Dick
We went about 3 feet above the roof. The vent was a "B" vent for propane and was centered in the casing by some galvy sheet metal I bent into a WWWWW shape. The cap kept out rain or snow. With this method you could weld a splitter/cricket to the casing and have it float above the roof so you wouldnt have any more penetrations.
Why not have a sheet metal shop fabricate some sort of "cow-catcher" that you attach to the roof just above the chimney? If it's stout enough and pointy enough it will split any sliding snow in two.
I vote for the cow-catcher idea as well. Good to separate the functions.
Forrest
Some great ideas! Keep 'em coming.How would you attach the cow-catcher to the roof? Through the sides of the up-turned seams?
I would screw them to the roof decking thru the panels using the same washerhead screws and sealant used with your decktite boot. You could possibly go thru the snap-loc ribs but it would be harder to get a connection that would take the solid whack that an avalanche will impart.
Take a look at the brace kits that come with metal chimney systems... arms designed to screw to the roof, etc.
Thanks for you thoughts. I have done my share of roofing, but this was my first metal roof, and maybe I am overthinking it.I agree that a secure washer seal-head screw through the metal and into the Advantech would be the strongest. But I worry about the thermal movement. On a hot day, the lower end of the panels, which are screw fastened at the top, grow maybe 1/4" relative to the wood deck. So, at the chimney maybe it's 3/16". Actually, per both the Fabral instructions and the boot instructions, I relieved the Advantech about 1 1/2" all around the boot flange, and the flange is screwed only into the metal roof.I did use one of the standard roof brackets to secure the upper half of the chimney, and probably will add another one lower down. As you can see from the pic above, I attached it to the side of the seams, and that did seem to hold up. The chimney is supported by a metal support at the truss lower chord, probably 4 feet below the roof line so when the snow hit the chimney, it buckled between the upper support and the truss support.Thanks again,
Dickps:
I just found this on the Fabral site:"There are three ways to attach snow guards to a metal roof. They can be screwed to, or thru, the
roof panels, glued on, or clamped on. Fabral does not recommend the use of screwed on snow guards.
On standing seam roofs they can restrain the designed thermal movement of the panel system. Also, if
they do get torn off they leave a hole in the roof. Glued on snow guards can be used, but they have a
tendency to come off. Also, sometimes they are installed with clear silicone sealant and many clear
silicones are acid cured and can damage the paint and metal substrate. Our recommendation is to use
clamped on snow guards. Fabral carries the S-5 snow guard system, which has been tested for design
strength on all of our standing seam systems. (See our S-5 Snowguard Systems Design and
Installation Manual, A-600, for details of the design and installation of this system.) When clamping
the S-5 or other clamping snow guard systems to our panels the installation procedures are critical. On
the S-5 system all the set screws must be installed from the same direction so the mounting bracket is
clamped against one side of the rib. Alternating sides on the bracket with set screws will deform the
panel side joint and can rip the panel under snow load. This was particularly true with our old bracket
that had 3 set screws. The new bracket with two set screws is more likely to be installed properly
since putting the two set screws in on alternating sides would badly twist the bracket. Also, even
though there are holes on both sides of the bracket, only two set screws are used and they are to be
installed from the same side."
Dick,
Cant help you on the chimney problem but also want to say thats a nice lookinig building.
I am getting ready to re-roof my 24x24 detached garage and was going to use the Fabral SSR like you have. How did it go up ? The instructions make it look pretty easy for anyone with a little skill. Mine will be on the existing 1/2" plywood deck after I strip the existing shingles. Did you use felt under yours like they suggest ? Any hints would be appreciated.Bill Koustenis
Advanced Automotive Machine
Waldorf Md
BillThis was my first snap-lock roof, so I am far from expert, But I can give you some first-timer impressions.
I was going to use one of the local roll-your-own guys, who use 28 or 26 ga, but I did not like the excessive oil-canning and generally sloppy appearance. The 24 ga Fabral 1 ½ SSR is much stiffer and better looking. At the time, the cost was the same, so it was an easy decision. You can also use one of the many ribbed snap lock panels. I helped on a barn that got than and it was fine.
http://www.idealroofing.com/pages_english/hf16-2025.shtml.My building was new and square, so all the panels could be ordered the same size, except for the few near the cupola and the many on the cupola and the little hipped wrap-a-round roof. You want to minimize handling and cutting. I used Rooftopguard 2 on this and the few roofs done since. This is my weekend project and I knew the roof would be exposed for a long time--as it turned out all winter. The rtg was like new. My panels were 30 feet long and hard to handle alone without buckling, but I rigged up a little stretcher from emt, which worked well to carry them. Yours will be much shorter and easier Look at the first picture. The panels come crated/strapped, and you can only handle one at a time without the crate “exploding” on you. I built up a simple work table from some old 2x4 pump jack poles screwed to sawhorses about 14” apart so the pans could rest upside done while I worked on them. After cutting to length, if reqd, you need to notch the ribs and bend the end down around. The Fabral tool--$15—works great. Cut the ribs with an angle grinder with a thin metal wheel but be careful to cut so the sparks spray away from the metal to avoid imbedded chips and rust. After preparing the ends, the panel is ready to go up on the roof. I had planned to prep all the ends in advance, but the handling problem soon convinced me to do them one at a time, then right up on the roof. It is very easy to accidentally bend a pan. I did the end prep and had my two sons on the roof. They snapped and screwed the panel down while I prepped the next one. I found the best way to get them up was to use a couple of the steel roof cleats with a light rope tied thru the holes, hooked on at about the 1/3 and 2/3 points along the length. . Easy to hook and unhook. Gotta keep the panels vertical and lift only from the topside to avoid bending. Two guys pull up ropes together. Didn’t drop any. We did the main part of the roof over a 3-day weekend. The second pic shows the beginning of day one, 3rd end of day one, finished up the east side. Second day, finished west side. Third day messing with flashings and cutting the last pans lengthwise to fit. The hipped cupola and the little roof took a lot longer—many many cuts.Tools—Angle grinder, but use it carefully and as little as possible to avoid the spark-rust problem. Other cuts, I used a nibbler from, I hate to admit, HF but it works well and I have used it countless times since.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=96661Also get a step drill like a Uni-bit to start the nibbler. I also build a little jig to drill two holes in the (bottom) end to be hemmed on either side of the pan. This made it easy to locate the cut for the angle grinder to cut the ears (cut the flat part with shears, left and right) and it also stress relieved the end of the hem, hopefully reducing future rusting. Use sheet metal vice-grips with cloth protected jaws to crimp the hemmed ends after installation. My impact driver got dropped on day one 20 ft onto concrete (I was not pleased), so the boys had to use normal drivers to install the cleats see pic. Advantec is very hard and I think some of those screws didn’t get fully driven, and there a few screw head dents in the panels. Watch that.
This is a scary slippery roof, esp if there is any pollen or junk on it. After a rain, no problem Slope is 6/12.Any particular questions-ask away.
Dick
Couple more pix
Hey Comanchero!
Nice hangar but it doesn't look like one with that hide-a-door. Is there a reason to that rhyme? Modern camoflage?
Peter
Maule MX7-180A
Went for that trick James Bond look. People are amazed when the whole side of the building goes up!About to build a house next to the hangar. Wife is particular. Hangar HAD to look good, ideally not like a hangar. It is in an area of nice houses, with neighbors not to happy about our airstrip. Even though it was there before they were--the old story. Miracle-truss would have been so much easier!The one-piece hydraulic door was a hassle, but it did allow windows on it since it did not hinge in the middle like a bifold. Door side is sunny south side. Tighter too in the winter. Future radiant floor planned.Hey-I like Maules, couple of friends have some. NH40 if you are ever in NH.
Dick
Miracle-truss would have been so much easier!
You ain't kiddin'! And bi-folds are more pleasant to deal with, particularly in the winter. I think I'd have built it that way, then hired a good artist to paint a really nice camo forest on the door. ;-) In any case, it's a unique and handsome hangar. And no one can complain about the usual industrial look.
I'm currently in Los Angeles on extended family business but I'll plan on dropping in on you after I get back. It's be nice to have another friendly destination in New England for one of my fly-ride days. I like to carry a bike(s) on trips. Usually leads to some interesting adventure.
Peter
Dick,
Thanks for the hints ! When I built the garage 25 years ago, I was pretty anal about getting everything square and the same size. They two roof decks are identical to within 1/8 inch so all of the panels should be the same length. When I talked to the Fabral dealer here he made it sound like a pc of cake for anyone with some decent skills. I have an angle grinder and will also use the Fabral tool for the ends. My garage is also 6/12 but it is low enough that I think I can get the panels leaned against the facia and then just pull them up or get a helper to push them up to me one at a time and then fasten them.
I like your cupola ! Was thinking of putting a small one on mine too. I am trying to plan everything so that as soon as it starts to cool off in late Aug or early Sep I can do this thing. I am going to order the metal and just put it in the garage till I am ready. I figure it will take me a good weekend to strip off the old roof, replace the felt and be ready for the new. If I can con some help, maybe quicker. I figure the Fabral should go up in a weekend easily. The first few pieces will be the learning curve, then it should flow pretty fast. Will definitely post pics when the time comes.
Thanks again !Bill Koustenis
Advanced Automotive Machine
Waldorf Md
Bill,
Couple other thoughts:
Make sure you accurately order up all the fancy Fabral flashings, channels, and especially take a careful inventory when you receive them. In my case, they shipped too much some stuff, not enough other and wrong items. Fabral was great, no questions asked, but it ended up taking three tries and 3 or 4 weeks to get it right and it held us up.I thought I'd be able to slide up the pans like you suggested, but they are very wibbly-wobbly and want to kink. Wind is an issue too. Yours will be shorter than mine and you may be able to handle it that way. I found the clip-cleats they supply clip perfectly into the female seam of the pan. Tie a lite rope thru the hole, clip 2 on (one near each end) and pull them up at the eave. They clip on and off in an instant and dont slip. With the pan pulled up by its edge ther is no kink potential. Prep all your pan ends, stack them on their edge on the ground next to the foundation and pull them up, 2 guys up and one down and it will be done safely in 5 minutes.Make sure the pamcake screws are down all the way on the cleats or you will get dents on the surface.
There is a very simple solution; it is used up here all the time to protect chimneys in similar installations to yours.
What you do is build yourself a wooden hook-ladder out of 2x4, and hook it over the ridge so it runs down the roof directly in line above the chimney. It doesn't have to be clamped on, screwed down, or glued in place, and it will prevent snow-slides in the track of the chimney, while allowing them elsewhere to keep static snow-load on the roof to a minimum.
The hooks should be about 2 feet long, and the connection of the hook arms to the ladder rails should be half-lapped, screwed, and glued very well as that's the joint that will take all the weight. (The rungs of the ladder can be inlet into the rails but it's not necessary; a couple of 20d nails or 3" x #12 screws on each side of each rung will hold the load that one rung will take.)
Don't place the rungs flush to the roof surface; set the ladder so the rungs ride atop the rails; otherwise they'll trap leaves and other roof trash trying to slide down the roof.
Dinosaur
How now, Mighty Sauron, that thou art not brought
low by this? For thine evil pales before that which
foolish men call Justice....
One thing on the photos: it looks like the braces were also bent by the snow load, since the chimney bent uphill. You might want stiffer braces as well.
I know the Simpson instructions recommend a snow shield separate from the flashing. (IANA expert, but I'm in the middle of planning a Simpson installation with similar concerns.)
You could stick the chimney through a roof curb.
This is a link to one company: http://www.patecurbs.com/catalog/index_s3.htm
You then fabricate an insulated metal cap and route the pipe thru that with a flashing. You can also have a welded cap/tall cone assembly fabricated.
The curb gives a solid anchor point to divert the snow, and you can specify a height. You can probaly have it clad with the same metal and finish that exists on your roof now.
Your current silicone flashing boot is useless for support.
Your photos are far too large for me to download on dial-up.
But we used to make up a lot of combo brace and cricket snow diverters. Think of the cattle gaurd on the front of the train in the old west movies.
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