I am planning on putting on my metal roof myself. My intentions were to use 1x4's 24" o/c as purlins and attach the roof one panel at a time, working my way down the roof line while standing on the 2nd floor. My roof rafters are 2x6, 24" o/c and are 13.5' long total. My plan is to attach the sheetmetal directly to the purlins. Is there any kind of vapor barrier that I need or will the metal do all I would need. I plan on putting in r-21 in the rafters. Will it need to be vented? I have heard that you don't need to vent a metal roof.
I just want to do it right. Thoughts, input, appreciated.
Just went through all of this on Christina's place.
Looks like 30lb or #30 felt to stop condensation. Jimmy Cason also has the problem. You could do it and have it foamed like Christina's place. http://countryplans.com/smf/index.php?topic=2991.msg43311#msg43311
Another option we do on steel buildings would be vinyl backed insulation sandwiched between the purlins and sheeting, although I haven't heard of it done on wood. It is my opinion it would work, but no guarantees.
If we're talking a house/cabin then yes, you need a barrier. Water vapor will condense on the underside of a metal roof if it's allowed to touch the metal. You need to keep the air away from the metal. Possibly the best way to do this is like Okie_Bob and Christina have done. Spray on foam. Icynene or other.
I'm going to do a metal roof. My method is going to be to construct a normal rafter supported roof with sheathing nailed in place to form a nice rigid roof structure. The wind blows hard at times up in my mountains. The metal will go over the #30 roofing felt, over the sheathing. Maybe that's just me.
Going the purlin route, without spray foaming the underside of the metal roof you will need a vapor barrier and an air space between the R21 fiberglass or cellulose in between your rafters. I've got a picture someplace I'll dig out and post.
A question for you... is code and/or inspectors involved? Christina's plans were interrupted by her code inspector. She had to modify her plans and her budget.
Here's the picture...
(https://i133.photobucket.com/albums/q75/djmillerbucket/oddsnends2/roofraftersinsulated.jpg)
This is shown with shingles but if you simply make adjustments for deleting the sheathing and shingles and insert metal roof and purlins the principles remain the same. You need the air space and the air entrance and exit points, UNLESS you seal the metal up with foam.
no code/inspectors involved at all. But, after reading the posts Glenn linked to, I think I need a vapor barrier. I don't get it, but it appears I need it. Why would tar paper stop sweating but metal won't? Odd.
I don't really want to spray in foam, it would be very cost prohibitive.
any tips on installing the metal correctly? I am going to use a snap-lock metal panels. They are 16.25" wide and will be 14' long. I am really concerned about it not being square or drifting off square. With 14' long pieces, I can't really follow a chalk line.
The ability of the steel to change temperature rapidly cooling in the evening with warm air underneath causes rain inside similar to a glass of icewater on a warm day. The warm air condenses (reaches it's dew point- turns to liquid) on the bottom of the metal making a pretty massive amount of water.
The felt does a couple things. It keeps the mass of warm air away from the bottom of the cold metal - slightly insulating, and if there is condensation on the metal, it will be drained safely outside of the house on top of the felt. If by chance a bit gets through - the felt will wick it out and allow vapor to slowly pass, besides allowing your venting to work without having to deal with the liquid rain.
Quote from: phalynx on January 29, 2008, 01:30:00 AM
any tips on installing the metal correctly? I am going to use a snap-lock metal panels. They are 16.25" wide and will be 14' long. I am really concerned about it not being square or drifting off square. With 14' long pieces, I can't really follow a chalk line.
How about making a jig from 2x4's and screwing it to your rafter tails to stop the sheets evenly, then remove it when done.
Man Glenn,, you are handy! I bet that would work pretty well.
Thanks. I have built around 300 steel buildings so have an idea or two of what could work -- even on a house. :)
I am also considering using spray foam (closed cell polyurethane) but I plan to place the metal roof over plywood or OSB sheathing. I am in Alaska so insulation is critical---would the foam allow me to omit an additional vapor barrier and also omit the usual ventilation space between the insulation and the roof sheathing?
If you have a good vapor barrier on the inside of the insulation, why would there be any warm, moist air under the metal when it cools off at night? Or are we just talking about outside air that enters under the metal during the day? Is venting really a good thing, if that's the case?
I'm wondering if I should use felt under the metal roof of this cabin that we will be building. The metal will be installed on runners over EPS foam insulation, so a little condensation isn't going to hurt the foam. Might it rot the runners, though?
I don't think there should be any problem with what you call runners. (Horizontal strips, if I interpret correctly?)
I base this on the fact that it is common practice here, when constructing a home with a tile roof, to build the roof in the following order... sheathing, roof wrap or building felt, wood nailing strips, then the roofing tiles. The strips are not continuous but are in sections with gaps to allow for drainage whenever necessary.
Here's an interesting technique aimed at building in a very cold climate (Alaska would qualify I think ;D ). This is from Building Science Corp (http://www.buildingscienceconsulting.com/designsthatwork/default.htm). They have produced several design techniques aimed specifically at differing climates. There is no one size fits all according to them. All their designs are aimed at energy conservation. They have many PDF documents available for download.
Not shown in the diagram is the ridge vent.
(https://i133.photobucket.com/albums/q75/djmillerbucket/construction/verycoldclimate.jpg)
That's a LOT of EPS foam!! :o
Hey MountainDon,
I always say the more EPS Foam the better.
The right insulation now will save a bunch later.
Build Smarter....EPS Structural Air
http://ergodesk.blogspot.com
http://styrihomenews.blogspot.com
Yep, Don. 1''x4'' wood strips to tie the foam down and secure the metal to.
phalynx If your metal has a rib or peak then it should not run off if it is not forced. It should lay perfect for the next piece to lock into. The main thing about metal is getting started square. If it is not then the end result can be very much to your dislike. If you sheeting or perlins are the same distance from you end rafter then decide how much overhang to aloow for the tin. I use 1" and 1-1-1/2" . Set a string line blocked out on each end to the desired overhang. Then move your tin after it is overlaped on the previous piece to that string line. Do not try to have too much of an overhang on the rafter tails or you will have to add extra facia to make the gutters work right.
If you want to double check yourself half way through the process you can pull it some to get back on track. Measure from the sheet edge to the last rafter or sheeting edge on top and bottom. If it is the same you are good to go. If you see that it is running off then when installing the next sheet attach the top or bottom( depending on which way it is short)and before screwing down that end just lift it slightly out of the groove while pushing toward the direction that you need and then attach the screw. You can also pull in this fashion by going tthe opposite direction. You would be surprised how much you can gain just a little at a time.
I know you can"t stretch metal but Oh yes you can of sorts.
Quote from: phalynx on January 29, 2008, 01:30:00 AM
any tips on installing the metal correctly? I am going to use a snap-lock metal panels. They are 16.25" wide and will be 14' long. I am really concerned about it not being square or drifting off square. With 14' long pieces, I can't really follow a chalk line.
The way we did it was to make sure that the first piece was as square with the roof as possible. That is the one that will determine how the rest of the panels end up, as they are all snapped togeter and have very little ability to move laterally.
First, we ran a string along the eave, and another up the gable to the ridge.
We marked 4' out on the long eave string, and 3' up on the short gable string. Then we adjusted the top of the short string to and from the gable end until we measured 5' diagonally between the marks. This established a square edge on the gable end. We lined the first panel edge up against that string, about 1/2" in from the gable end.
After placing the first panel, the rest just snapped/screwed in place, measuring the overhang at the bottom to keep it uniform for each panel.
The last panel wasn't more than a half inch or so off of square (could be the roof, rather than the panels). It all worked very well, and was much easier than any shingle roof I have been involved with.
(http://www.arizonaranch.org/Process/little_house/images/aug07/first_panel.JPG)
(http://www.arizonaranch.org/Process/little_house/images/aug07/roof_north.JPG)
Quote from: Redoverfarm on January 29, 2008, 07:16:04 PM
phalynx If your metal has a rib or peak then it should not run off if it is not forced. It should lay perfect for the next piece to lock into. The main thing about metal is getting started square. If it is not then the end result can be very much to your dislike. If you sheeting or perlins are the same distance from you end rafter then decide how much overhang to aloow for the tin. I use 1" and 1-1-1/2" . Set a string line blocked out on each end to the desired overhang. Then move your tin after it is overlaped on the previous piece to that string line. Do not try to have too much of an overhang on the rafter tails or you will have to add extra facia to make the gutters work right.
If you want to double check yourself half way through the process you can pull it some to get back on track. Measure from the sheet edge to the last rafter or sheeting edge on top and bottom. If it is the same you are good to go. If you see that it is running off then when installing the next sheet attach the top or bottom( depending on which way it is short)and before screwing down that end just lift it slightly out of the groove while pushing toward the direction that you need and then attach the screw. You can also pull in this fashion by going tthe opposite direction. You would be surprised how much you can gain just a little at a time.
I know you can"t stretch metal but Oh yes you can of sorts.
The pan deck sheeting will be a little harder to stretch or shrink , but John is right -- you can stretch or shrink a bit by how tight the ribs or standing seams are pulled or pushed allowing you to pull them the same distance from a check line top and bottom. In low wind conditions I sometimes screw a few sheets together without fastening to the purlins to prevent sawtooth then measure the eave or match a string line and check line, then fasten the front edge in the proper place and go back and install the rest of the screws. That was on steel buildings - low pitch -- steep pitch is much harder so that will probably be of no use to you. Still wanted to get the info out though.
rdpecken
What color do you call that shown in the picture? Unusual but I like it. I am sort of tired of the Forrest Green and reds used today. Thats why I went with a burnished slate.
I just realized. I bought the edge trim pieces like you showed in the green roof picture. What I didn't think about was the overhang. I planned on having just a 6" overhang. I was just going to extend the purlins 6" over the gable end wall. I was then going to attach the sheet metal to it. Now, the problem I see is I didn't create a facia board on the gable ends like you did. Will this be a problem with the edge trim pieces or will it work fine/look funny.
(http://www.ouramericanadventure.com/coppermine/albums/house2/DSC_6746.jpg)
I think it will need the board or be floppy and not able to be squared.
Glenn I would imagine that the tin you used was a little heavier than residential tin (29 ga) that would allow you to walk between perlins without it bending. I just worked off the perlins. Tried to work from the floor and scaffolding but a real pain moving the scaffolding every couple of sheets plus you really couldn't reach all the screws either. But my porch was 3/12. The cabin main I used my Duetz and a ladder in the bucket laid against the roof sheeting. ;D
Quote from: ergodesk on January 29, 2008, 04:39:50 PM
Hey MountainDon,
I always say the more EPS Foam the better.
The right insulation now will save a bunch later.
Build Smarter....EPS Structural Air
http://ergodesk.blogspot.com
http://styrihomenews.blogspot.com
Interestng info, ergodesk. Second link didn't work.
We used 26 gauge - occasional 29 on odd jobs. We worked on the roof on 1/12 or 2/12 pitch. When I did my garage --12/12 I worked off the purlins and a fold down ladder along with a forklift meat catcher at the bottom where possible.
My sheetmetal is 24 guage. Will that be less floppy? There will be 1x4 purlins extending out with the sheet metal.
A little less- the only problem I see is that the bottom edge of the trim is usually screwed to something to keep it square. It may or may not sit square by itself on the top of the rib. Possibly spacers on top of the sheet on top of the 1x4's could give you a way to keep it square but it depends on how the trim comes out in relation to the sheeting and if the trim is a tight fit on the rib or is taller which would allow it to sag more without the bottom edge screwed. There is the possibility of the wind coming up under it and folding it up over the roof also.
phalynx I was just making a comment about Glenn screwing the sheets together then going back and attaching them to the perlins. He could easily walk on a lesser pitch to fasten the sheets to the perlins. You will be OK with 24 guage. Had you considered putting a false rafter in your 6" overhang that you would attach the facia tin onto. Just watch that you do not end up with more roof than you have tin or you will be having to cut 6-8" off one side to slip under the next to last piece to make it work. Another option might be to figure a wider overhang on each end and one more sheet of tin to make it all come out right.
If you don't get anything else out of your inquiries think square. I have seen buildings where the tin is 1-2" overhang on the gable ends at the bottom and 4-5" at the top and worse. But if you start off with the same amount of overhang on the end(ridge and tail) and hold the bottom to a string line and your roof sheeting is fairly square you will be fine.
I forgot to ask if you are putting a ridge vent or ridge cap?. That makes it a little more forgiving if the tin falls a little short on the ridge end.
Quote from: Redoverfarm on January 29, 2008, 11:26:42 PM
phalynx I was just making a comment about Glenn screwing the sheets together then going back and attaching them to the perlins. He could easily walk on a lesser pitch to fasten the sheets to the perlins. You will be OK with 24 guage. Had you considered putting a false rafter in your 6" overhang that you would attach the facia tin onto. Just watch that you do not end up with more roof than you have tin or you will be having to cut 6-8" off one side to slip under the next to last piece to make it work. Another option might be to figure a wider overhang on each end and one more sheet of tin to make it all come out right.
If you don't get anything else out of your inquiries think square. I have seen buildings where the tin is 1-2" overhang on the gable ends at the bottom and 4-5" at the top and worse. But if you start off with the same amount of overhang on the end(ridge and tail) and hold the bottom to a string line and your roof sheeting is fairly square you will be fine.
I forgot to ask if you are putting a ridge vent or ridge cap?. That makes it a little more forgiving if the tin falls a little short on the ridge end.
The thing about tin not fitting the roof you should have been getting the mesage that it won't a long time before hand. If you have been triming plywood to fit and other boards that were all the same length but for some reason not fitting in place. there should have been a red flag your out of square. Buildings all start at the foundation. if it is not square and level the rest will have to be adjusted during the whole building process. That is why it is so important the time is taken to do the first part right no matter what. Don't ask me how I learned this a long time ago! Mark
Quote from: Redoverfarm on January 29, 2008, 10:44:41 PM
rdpecken
What color do you call that shown in the picture? Unusual but I like it. I am sort of tired of the Forrest Green and reds used today. Thats why I went with a burnished slate.
Actually, that is the Forest Green supplied by AbsoluteSteel in Tempe, AZ. http://www.metalroofingsource.com (http://www.metalroofingsource.com)
I like it. It's kind of dark.
Just didn't look like that green it looked darker. Might have been the photo, time of day or sun. They have a dist in Lancaster Pa which is not to farm from me. But that is steel country anyway. Keep us posted.
When we started putting on the roof we had no idea, the roofer put us off for to long and we decided to do it ourselves.
To hold the metal up we used L brackets made out of 2x4's clamped on to the end of the rafters and leveled leaving a 2" overhang. We chalked a line across the top of the rafters at 17' 10" squared up. After I screwed in the roofsheet on the top to hold it and adjusted to the chalk line. After the 1st one we just moved the brackets to hold the next sheet level. I tied off to the ridgebeam so I just moved up and down the metal. I hope this makes since, we did it on all 3 roofs and square on all.
(http://[img]https://i263.photobucket.com/albums/ii125/mo981/Picture028.jpg)[/img].
Quote from: Mo on February 09, 2008, 09:01:25 PM
When we started putting on the roof we had no idea, the roofer put us off for to long and we decided to do it ourselves.
To hold the metal up we used L brackets made out of 2x4's clamped on to the end of the rafters and leveled leaving a 2" overhang. We chalked a line across the top of the rafters at 17' 10" squared up. After I screwed in the roofsheet on the top to hold it and adjusted to the chalk line. After the 1st one we just moved the brackets to hold the next sheet level. I tied off to the ridgebeam so I just moved up and down the metal. I hope this makes since, we did it on all 3 roofs and square on all.
(http://[img]https://i263.photobucket.com/albums/ii125/mo981/Picture028.jpg)[/img].
What ever works and if by yourselt that sounds like a good way to do it. I allways put one screw in a top corner till I have the sheets up and all square. Then I go to the bottom edge line them up put in another screw and then finish with the rest of the screws. That way it is easy to correct a problem. Mark
I had 2 people helping me but they didn't want to get on the roof. I took a knot tying class at the local climbing school and tied off the center of the ridgebeam. You need to make sure you push the metal out from one side to the other as you put the screws in.By the 30th sheet you will be really good though. This is our cabin. It is a modification of Victorias Cottage. :) The roof is my roof the cabin is ours
(https://i263.photobucket.com/albums/ii125/mo981/Picture028.jpg)
Nice job, and great that you could handle the roof. Some folks have a real bad time with the height.
Thanks. I was the 1 out of 3 that didn't mind. The side room was added 1 year after the main. 32' to the smack didn't seem exciting to the Just Helping friend.
Mo
Great looking place, like your siding. I want to do board and batten, I'm leaning towards reverse though with the batten underneath.
I haven't installed metal before but am leaning that way, most everybody that I know say they would go that way. In regards to what Willy said about doing it right from the start. Seems to me it would be easiest to measure your diagonals when you just had the rafters on and then you would have a idea of where you are. My 2 cents worth.
Mike
Thanks, we were going to do reverse but after reading many posts and looking at other cabins we decided to do it this way. We put on black paper, then perlins and decided to put the wider boards next. We used screws and covered them with the battens. No warping.
We did measure that way but only the outside rafters. Measured. Plumbed. Measured. Chalked.