Tin Roof Questions / Mistakes

I learned this one the "hard" way. Did pay off a year later, though... fella was building a gold plated boat house on the rich folks development east of me, and I mentioned his roof was gonna leak. He didn't believe me. I told him to call the manufacturer, about using their product on top of pressure treated lumber... the next morning, he had the builders out pulling the roof, and redoing it... got me the job as the electrician on site. One of those cost ++ jobs .

Nel... it's great to tackle a project DIY. It's real easy to check out a book from the library first, to see the 'regular' way to do something. Lots of basic building idea's are online. About the only time I do something without consulting the pro's, is when nobody's ever tried doing something like I'm trying before. Don't be afraid.

btw... a lot of the work I get, is from folks who jumped on a project and couldn't finish... they call me to come rescue them... I like rescue jobs!

good luck in gettin her fixed...

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Luck is what happens when preparation meets opportunity. Seneca
Learning is not compulsory... neither is survival. W. Edwards Deming

Next question is re the "pitch" of the roof: Today the children and I took lots of pictures and met with a very nice roof man and a contractor who agreed to give suggestions. As per their instructions, we took measurements and.......if we are correct.....then we need to re build the whole roof OR lower the deck area.......since it seems to us as if the "pitch" part is way way too low.

But we are not sure how to find the "pitch" --

At the house end of the porch......where it meets the old part of house......it measures 9 feet 4 inches from floor to tin roof........5 feet later it is 8 feet 7 inches from floor to tin.......and so forth till end at 6 feet 10 inches......

Said another way........ it is 9 feet 4 inches at the start.......and 16 feet 10 inches later (the width of the porch....or would that be the length..).....it is 6 feet 10 inches.

So - the boys are saying the "pitch" is only 30?

And the contractor and roof man said to have a proper pitch for a tin roof, we had to have 68 inches LOWER at the end......than at the beginning........and we only have 30 inches lower

So - how do we say what our "pitch" is?

Thank you everyone for help with this one.

(NOTE: we do have, up above the shed roof we built, a pitched roof part of the 2nd story of old part of house, we did the shed roof for the porch since there was an old small, only 5 foot shed roof porch there and we wrongly though we could just follow that shed roof line.....but that was before we learned about "pitch" -- soooooo --- we may just tear off the shed roof and go Up up up and make the roof just follow the pitched one.....but first we want to see if we need to abandon the current plan......

and yes we are still learning and having fun with this one.....we stopped and picked up some more free wood out of a sawmill trash pile on the way home to subsidize the project.....

Nel, How far west are you in western NC? What size lumber and what spacing are the rafters in this project?
Provided you are not in a heavy snow area and provided the lumber supporting the roof is adequate you can get by with as little pitch as 1' in 12' provided the flashing and caulking is correct. If you will look around at the metal building that appear to be nearly flat they are 1 in 12 and they are very common here in NC. I would use screws when reassembling and even with the neoprene washers I would apply some caulking in the used holes as you reassemble.

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Agmantoo
If they can do it,
you know you can!

Well let me completely mess it all up by saying I never screw or nail into the ridge on any metal roof or siding. It just makes no sense whatsoever to nail or screw into a ridge, which is 1) not firmly against the backing board; and 2) won't allow the gasket to fully seal.

I always nail -- or preferably screw -- into the flats, close to the ridge. By doing so, I draw the gasket and tin up TIGHT against the underlying board. I use screws whenever I possibly can, because they are superior, and I rarely have a leak (last one I did was a 40x40 building, had 3 leaks). If there is one, it will be a very small weep, and a caulking gun loaded with 100% clear silicone sealant takes care of those without compromising the color of the roof.

I fully realize that where you nail or screw is controversial, but I can show you two shop buildings side by side. One was nailed into the ridges, one was on the flats. The ridge-nailed building will need soon to have the trusses replaced from all the leaks. The flat-nailed one is tight as a drum.

One possible solution to your leak problem is simply to get up there with several tubes of clear silicone, bring some rags to wipe it off your hands, and coat every nailhead with your finger. This is superior to the paints, which eventually crack with expansion. Most 100% silicone is good for 25-50 years.

The best stuff to use under metal to prevent weeping is double-bubble insulation BEFORE the metal is laid, but it may be too pricey for some. If your metal is already up, you can staple plastic up on the underside BEFORE adding insulation, to serve as a moisture barrier. This will not be as good as having the barrier between the metal and wood, but it will be better than none at all.

It is adviseable to use something under the metal as a vapor barrier, even if it is an outdoor roof, to prevent it from raining condensation on your head.

A metal roof ought to rightfully have at least a 4/12 pitch. What that number means is the distance the roof falls for every inch of its length. A 4/12 falls 4 inches for every 12 inches of horizontal length. So for example, a 4/12 roof that was 14 feet off the ground at the high point and covered a room 10 feet wide would be 10 feet, 8 inches off the ground (not including any overhang) at the low side wall.

Metal can be successfully used for roofs of 2 inches pitch or less, but it should be D-seam or standing-seam for such shallow roofs. V-seam, which is the cheapest but also most troublesome of all metal configurations in my opinion, almost requires a 4/12 minimum pitch to properly drain and remain leak-free for any lengthy service time. I have seen V-seam successfully installed with silicone laid on the laps to seal it with some success on shallow roofs, but for the added cost, I'd just go with a D-seam.

Hope this helps you some.

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Jim Steele
Sweetpea Farms
"To avoid criticism, say nothing, do nothing, be nothing." -- Robert Gates

Nel, according tyo what you provided, over 10 feet you lost 18 inches, which is a 1.8/12 pitch...roughly 2/12. If you DO remove the tin and start again, do this:

-- Lay a bead of 100% silicone between the laps.

-- Use screws, and dab each hole with the silicone before screwing them in. Screw them straight in. I guess if you nailed the ridges, you will have to again. Just make sure the nails are coated with silicone, with no gaps because of the ridge.

Use a moisture barrier. I prefer the double-bubble, but tarpaper or plastic can work, too.

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Jim Steele
Sweetpea Farms
"To avoid criticism, say nothing, do nothing, be nothing." -- Robert Gates

jim s ur crazy what happens if you miss and the nail or screw dont hit any thing under then you a have ahole that will leak if you miss one one a ridge and leave a hole it wont leak and any one that knows about roofs will know its better to put them in the ridge have been in many a barn and looked up and could se daylight through nail holes in the ridges and there was no leaks. am i right people or wrong water cant run on the ridge very well it will fall off but in the flat it will leak for ever.

Thank you everyone -

We measured the tin from the top side (placing tape measure against house wall and then out to end of tin) and it measures 20 feet 9 inches. (we have a 2 foot over hand on the end to keep water away from our lower path) I am trying to find tin that long but so far cannot and will have to wait till morning to call other places now. Home Depot and Lowe's only carry it up to 16 feet long.

Agmantoo: We are near Asheville / The lumber is treated 1 X 4 "slat" pieces over treated 2 X 6 "joists" (not sure if that is correct term or would it be rafters?) ......over a 2 X 8 treated "header" piece.

I am confused still about the "pitch". We found a graft on internet and it said we have a 4 / 12 pitch? My son used a level and held it against the tin, leveled it, measured the distance from level to the roof and it was 4 inches?

We have determined there are nail holes, and the flashing must be removed.......so we are going to remove all the tin and start over with the current rafters / slats.........and we will add the plywood base / then.......we are still reading.......

If someone could help me figure out the "pitch" still it would help. Thank you

Okay, here it goes.

To calculate pitch, thing of your porch roof as the hypotenuse on a right triangle. (call it side AB). The wall of the house forms another side of the triangle (call it side BC). The next side of the triangle (side CA) is an imaginary line from the lowest point of your porch roof to the wall of your house, parallel to the porch floor.

Your pitch is the length of BC over the length of CA. Most roofers express it as if CA is 12 feet. You have a side BC of 30 inches over about 200 inches, so it is less than 2/12. That is a low slope roof.

By way of comparison, a roof with an angle of 45 degrees is 12/12. If you did a 45 degree angle on your roof, your side BC would be 16 feet plus. That is quite a steep roof.

The steeper the roof, the less likely it is to leak. If possible, you should try to frame it so that it is at least 4/12. Otherwise, you need to do a good job flashing and seal up all the holes.

Hope this helps.

Thank you -- we do have a few more inches we can build up on the upper side and that will help. Thank you to everyone.

Jim S, I agree there is some controversy on fastening into the ridge or the flat of the tin. On a wall I'd do the flat every time. Here at this farm most of the 10 out buildings were tinned 30+ years ago & nailed into the ridges. It has worked well here in the heavy snow zone. I would be reluctant to change to nailing - er, screwing prefered - the flats of a roof, tho I understand many are doing it & it should work fine. I guess it is easier for novices to deal with the flats.

I'm not familiar with the D ridges you mention, is that a regular term, or could you point me to an internet pic of the different types of roof ridges? Standing I know, and I assume what I am familiar with is V, but not sure on what D is....

--->Paul

Pitch is just a handy number that tells people how steep the angle of your roof is. It tell 'everyone' how much angle your roof has. It is expressed as how much fall in every 12 inchs of roof. a 12 in 12 roof would be a 45 degree angle, dropping 12 inches for every foot of length. A 1 in 12 roof would have very little angle, dropping only 1 inch in every 12 inches of roof.

The level was good idea. The question is, how long was the level? If it is a foot long level, then the pitch would be about 4. However, if the level was 2 feet long, than the pitch would be 1/2 that, or a pitch of 2 in 12. (2 inches of drop for every foot of length.)

Your measurements from both ends would indicate you have a pitch near 2 in 12, and we can guess your level is 2 feet long?

--->Paul

Rambler: He must have measured wrong.....plus he now points out that we have a 7 inch floor drop.....so he is going to use level and try again. He keeps saying we have a 4 / 12 drop but everyone else says it is 2 / 12 or a bit less than 2 / 12.

We have help on the way this weekend (husband and 4 buddy's) and we are going to try to add a few inches at the top to help the drop.

Its been a good math class in any event! Thank you again everyone.

We are off to the salvage place today for doors and windows.

I don't think your pich will be a problem especially if the rafters are strong enough. You will encounter possible heavy snow loads in Asheville area but it should slide off of your roof pretty easily, that's another thing about metal roofs.
Go to www.metalroofing.com for a forum on nothing but metal roofs and links to metal roofing manufacturers. They will give you correct info on the manufacturers suggested installation and insulation of metal roofing.

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"Education is the ability to listen to almost anything without losing your temper or your self confidence"
Robert Frost

To help hit the rafters, mark the tops with a small piece of masking tape. You should be able to see the bottom if you install the flashing or drip edge last.
A chalk line snapped on the metal while centered over the rafter will eliminate missing the rafter with your S.S. screw/washer combo