I have a 55 foot long shed that gets a new metal roof tomorrow (my first roof). I’ve put down battens on 2 foot centers. The old shed has a few waves or ripples in it due to 1)sagging rafters 2)an inadequate beam when first built 40 years ago and 3) it was built at two different times several years apart. I’ve read the instructions carefully and they indicate to start at the “lee” end and work to the prevailing windward or weather end. Some of the guys in the neighborhood who have stopped by to render free advice suggest starting the panels in the middle and working out to the ends to even things out. I’ve squared up with the 3-4-5 method and popped lines. The building is fairly square. Should I follow the instructions and start at an end or start in the middle? Arguments for or against either way? I plan to pre-drill the stuff and start screwing it down bright and early tomorrow. Thanks.
Keith
Replies
Follow the manufacturer's instructions; ignore your helpful neighbours. By starting at the leeward end of the roof, the laps between panels will be shingled downwind, which is what you want to help prevent wind-driven rain infiltrating the lap joint.
The other thing you should do--which should be mentioned in the mfgr's instruction sheet, but do it even it it is not--is to run a bead of butyl rubber sealant down the entire length of each lap joint. (Easiest way to do this is with a pneumatic caulking gun but a manual gun will work, of course.) Flip over each new panel before you install it, and run the bead of butyl down the underside of the ridge that will lap the last panel. Then flip the panel back over and line it up for height before you the lap the ridges.
If the roof is very steep (12/12 or steeper), failure to seal the laps may not cause you to have capillary leaking through the laps, but I wouldn't want to bet the farm on it. You should definitely seal the laps for any medium (10/12 to 4/12) pitch. (I would not use screw-down steel at all under 4 in 12.)
You may have to get the butyl from the company which supplied the steel roofing; most hardware/big-box stores don't carry it (at least around here). Don't substitute a silicone or latex or thermoplastic caulk; butyl is the only sealant flexible enough at all temperatures to take the expansion and contraction that steel will go through.
Last bit of advice: Don't overdrive the screws; it distorts the ribs and spreads the sheet out unevenly, so if you do too much of it by the time you get to the other end of the roof, you'll be off parallel by an inch or two or more. Drive the screws just enough so the rubber washer starts to squash, and stop. A small, cordless impactor is the ideal tool for this.
Dinosaur
How now, Mighty Sauron, that thou art not brought
low by this? For thine evil pales before that which
foolish men call Justice....
Thanks. I'll follow the instructions. I've already gotten the seam caulk and plan to use it. I appreciate the advice. Keith
H'lo keith_n!
Dino's advice re: not overdriving the screws & using a cordless impact driver are good.
Depending on how you finish the gable ends you may want to plan out your sheets so the last sheet finishes down. By that I mean that a high rib does not fall at the edge of the roof. With a long tape you can keep track of your sheet spacings so your end sheet will finish the way you want it. It is rather easy to stretch or shrink your sheet spacings a bit to achieve the final placement for the last sheet, you do have to keep track of it as you go, however. Unlike flat panel sheathing (ply, OSB etc.) you can't just run the steel "wild" & cut it off after it is all down.
If you happen to miss one of your battens with a screw & it is loose it can become a leaker, take it out & seal the hole right away before you forget to. These things have a way of fading from your memory. I would make up storey poles of plywood strips with hash marks drawn on to indicate batten spacings if your help aren't all that careful about eyeballing the screw centerlines. (I happen to appreciate a straight line of screws & feel that adds to a professional install)
If you want to get really retentive about things you can make up some wooden support blocks that match the profile of your sheet to use to keep the sheets tight in the joints at ridge & eves. Use a couple of long reach Vise Grip type C-clamps to clamp the two sheets to the support blocks as you screw the ridge & eves down, before filling in the rest of the "field" of screws. This will go a long way to help keeping the seam an even spacing. I think that is more important than following the line of the eve if you will have a gutter anyway.
If you start at the ridge & progressively install screws down the seam, for example, it is difficult to keep the seam from spreading by the time you get to the eve. screws.
Sincerely,
STAINLESS
>>I would not use screw-down steel at all under 4 in 12.<<
I've used Galvalume and standing seam on as little as 2/12 and never had a leak. Usually used rosin paper or felt over decking for those instead of purlins.
I've used Galvalume and standing seam on as little as 2/12 and never had a leak.
Yet. You probably would have in heavy snow country. I doubt the rosin paper made a difference. Felt may have. http://grantlogan.net/
It takes a big man to cry, but it takes a bigger man to laugh at that man. - J. Handey
We generally have little snow, mainly ice.
How would heavy snow cause capillary action? Wouldn't the seams freeze?
I'm kind of ignorant about that.
How would heavy snow cause capillary action?
Don't know that it would. But an ice dam out by the eave can back melted snow way back on the roof on a low pitch and put the seams under water.
edit: Also, the lower the pitch, the slower the water evacuates during heavy rain. So, in a deluge, the seams could potentially be under water. These two items are the reasons most metal roofs are not approved (by the manufacturers) for less than 3/12.
http://grantlogan.net/
It takes a big man to cry, but it takes a bigger man to laugh at that man. - J. Handey
Edited 11/4/2007 9:09 am ET by seeyou
I like to pre drill the screw holes a fuzz over size - helps keep the metal from working the screws out as much. Clamp the sheets together when you drill them, you'll save on broken bits - have fun and don't fall off.
>>I would not use screw-down steel at all under 4 in 12.<<
I've used Galvalume and standing seam on as little as 2/12
When I say 'screw-down steel' I'm referring to factory-formed steel, not true standing-seam metal roofing. There are no locked and soldered seams in that stuff, just lapped ridges; the only thing keeping the water outta the house is a good, steep pitch.
On a low-slope roof, anything that obstructs or slows runoff--ice dams, chimney or vent penetrations, accumulations of leaves or pine needles--will create pooling, and capillary action will then suck water up into the lap joint below the neoprene washer under the screw heads.
Dinosaur
How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....
I only use butyl for less than a 5/12 pitch and never aleak.I also prefer butyl tape instead of caulk. It is neater to work with and will stay in the right place. A novice using too mucch butyl or getting it slightly in the wrong osition could easily end up filling the crimp that is designedto lead the capilary water off the roof
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
also prefer butyl tape instead of caulk. It is neater to work with and will stay in the right place. A novice using too mucch butyl or getting it slightly in the wrong osition could easily end up filling the crimp that is designedto lead the capilary water off the roof
I use it on any screw-down steel I touch; it's cheap insurance and with a pneumatic caulking gun, it takes about 30 seconds to run the bead right down the underside of the lap seam. On the job we just finished last week, I used 7 tubes of butyl at $4 a pop for 1000 sf of steel; it probably took me all of 10 minutes extra to apply. For $36 bucks extra, the client ain't crying and I can sleep sound even if her tenants fail to shovel off the roof like the lease specifies.
I've never seen butyl tape, though. Tell me about this stuff.
Dinosaur
How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....
Doing the caulk from backside is definitely the way yo do it. Fitting the gun tip to an inside crimp guides the gun straigh instead of hjaving it wobble all overon thehigh top of the female side of the lap. And it is less likely to get it on anything else that it should not be on.The tape comes on a roll about 1/2" or 5/8" wide. It has a waxed paper between like ice and water shieled does, so you can roll it into place, cut it off, and then strip the waxed paper just before placing the steel. It is gummy like chewing gum
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Thanks; I'll see if I can find someone up here who sells it; might be handy to have around.
But Santa's gotta find you a pneumatic caulk gun fer Xmas. I can see using tape on small repairs or patches where you don't want to open a whole tube of caulk for a seam or two, but I would not use it for a whole roof (unless the alternative was to squeeze the handles of the Cox until my forearm fell off...).
Dinosaur
How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....
http://www.alibaba.com/showroom/Butyl_Rubber_Tape.html
They can't get your Goat if you don't tell them where it is hidden.
You will make your life miserable by starting in the middle. The lapps are male/female.
Use some vice grips to handle it and to emp cinch each sheet to the previous. That holds it in place while you screw.
Pay attetion to staying aprrallel. Each sheet will want to turn downhill slightly, so I cclamp the grips top and bottom on the lap, then set my first screw near the edge away from the lap so that the triangulation is holding the sheet exactly wqhewre I want it. I check measure to opposite edge of roof every 3-4 sheets
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!