Installing 5V roofing tin

WV Sawmiller · March 30, 2024, 11:16:27 AM

Question - can you install 5V roofing directly to a solid wood roof or do you need air flow under it?

I am going to be replacing a roof on my upper shooting house. It is a 6' square elevated building with an 8' square badly leafing shingle roof. I have ordered 4 sheets of 8' 5V tin to replace the roof. I plan to tear off the existing roof and put a solid roof on of 4/4 rough poplar lumber. Because of the distance and slope I have to carry the wood and metal I opted for 5V tin instead of wider sheets I use most of the time.

In the past I always put metal roofs on wooden nailer strips and they were open underneath. If I need the air flow I can either add some 1X4 strips on top of the roof or just use 2X4s every couple of feet between the 4/4.

Any experienced recommendations will be appreciated.

beenthere · March 30, 2024, 12:13:02 PM

Without the air flow, how will you deal with the condensation ? Or will 5V not have condensation from the changing temps??

Magicman · March 30, 2024, 12:54:13 PM

Yes it will drip (condensation) inside because of the temperature difference. It will be minimal but it will still happen. There is a thin layer of insulating material that you can lay that is shiny in the top and whatever underneath that will prevent this. You can lay felt between which is not as good but better than nothing.

I am saying what you should do and I did nothing. It drips, but it ain't much and I ain't changing it.

moodnacreek · March 30, 2024, 01:03:09 PM

Put any rough 1" boards close and black paper. Screw through the highs always. All my low screwed roofs leak after 15 years or so and walking on them is not fun with the purlin boards 2' on center.

Larry · March 30, 2024, 01:08:56 PM

Thirty years ago I built a house and had true standing seam installed. It is similar to 5V except for the width of the panels. The roof was osb with a layer of heavy roofing felt than the tin. I sold the house but the roof is still in place. I never had one problem with it and still looks good today. Probably the best roof I've ever had.

With standard roofing on out buildings I have went to 1/4" fanfold insulation under the tin. This stops any condensation and cuts the summertime heat a lot. I used a Dow product mostly, but think it is discontinued now. This looks like the same stuff. fanfold insulation

Magicman · March 30, 2024, 01:50:58 PM

Quote from: moodnacreek on March 30, 2024, 01:03:09 PMScrew through the highs always. All my low screwed roofs leak after 15 years or so

My experience and recommendation is the exact opposite. Maybe it's the glaciated stuff up North??

Don P · March 30, 2024, 03:33:08 PM

Where does the condensation come from?

WV Sawmiller · March 30, 2024, 03:58:08 PM

Sorry Lynn but I'm with Moody on this one. I was always taught to nail into the peaks although I see lots of folks nail into the flats. When the washers deteriorate in a few years (I guess there are no more lead head nails like we used when I was a kid) the nail hole will leak.

I usually tap the peak with my hammer to make a small flat dimple and put my screw there and screw it through. If/When the rubber washer deteriorates the screw is still on a peak and the water is shed to either side and cannot pass through the hole.

I've been considering whether to put tarpaper down on the roof then nailers on top of that with the 5V on top of and nailed through the nailers but I'm planning on using green stock lumber and it is going to shrink and would tear holes in the tarpaper. Also I only have an 8' square roof (64 square feet) and the tarpaper only comes in rolls that cover about 400 square feet.

I think I'll put the roof on then nail nailers to that then the metal which will give a 1" gap for air flow between the metal and wood. I know it will condense some but should not be enough to rot the wood out during my lifetime.

There is a very good chance I will put the materials on top then finish that and have to shinny down a slender beech tree next to my landing. I keep thinking of Tom's video of Inga and Bill on their "Elevator trees" .

When I think of that option I keep remembering a coon hunting trip trip Labor Day night in 1976 just before I left for the USMC. My dogs had treed up a slender tree and left after other coons. We determined it was a baby coon and my buddy said "Let's catch him" which means "You climb up in the tree and grab him while I stay below and watch". (He is now the VP of a Bank/Credit Union so you can see where this is going.) I climbed up the tree till it was about an inch in diameter and leaned on a big Cypress too big for me to climb and the coon was at the tip and about the change trees so I yelled at my buddy I was going to shake him out and to grab him when he hit. I shook, the coon fell past me but without the support of the cypress my tree bent sharply and quickly and I tried to shinny down till "CRACK" the tree (and Me) fell out in the middle of the mud and cypress knees and the dogs who had returned. My buddy was chasing the coon but his light fell apart. I stood up in the pitch dark and leaned against the cypress tree for support and when I did I felt fur and grabbed it and caught the baby coon who was trying to escape again. He then squalled and I had all the dogs trying to climb up me, I finally got them kicked back, my buddy got his light back together, I took off my knee high rubber boots and took off a sock to roll the coon it (Socks and shirt sleeves make good catch bags if you don't have a corn sack) and we headed out.

All was well for about 100 yards till I stepped on something that was whacking my leg and I looked down and found I was standing on about a 36" cottonmouth who was striking my R leg. The only thing that saved me was my floppy boot tops. He was hitting them but did not penetrate my leg. I set a new state record standing high jump, came down and got my 10/22 Ruger rifle unslung and proceeded to empty the clip till the snake expired then we continued our hunt.

I don't need that kind of excitement at this stage of my life.

Quote from: Don P on March 30, 2024, 03:33:08 PMWhere does the condensation come from?

The metal gets hot then cools and it gets moist on the bottom. I had the same thing with dripping copper water pipes in my basement till I wrapped them with foam insulation.

SawyerTed · March 30, 2024, 04:13:16 PM

Got any unused asphalt shingles? Throw a layer on before the metal, aggregate side down. Put the metal on.

You won't ever have to worry about the roof again. Condensation shouldn't be an issue. The shingles don't even have to lap like a regular roof.

Magicman · March 30, 2024, 05:22:18 PM

Quote from: WV Sawmiller on March 30, 2024, 03:58:08 PMSorry Lynn but I'm with Moody on this one.

No argument from me nor any reason to apologize.

When we put tin down with nails we nailed through the peaks. With the captured neoprene screws, I know of no professional roofer that does not screw through the flats. If the lath is 1X4's they use 3/4" screws. If the lath is 2X4's they use 1 1/2" screws.

Old Greenhorn · March 30, 2024, 06:02:26 PM

Quote from: WV Sawmiller on March 30, 2024, 03:58:08 PM.......................

When I think of that option I keep remembering a coon hunting trip trip Labor Day night in 1976 just before I left for the USMC. My dogs had treed up a slender tree and left after other coons. We determined it was a baby coon and my buddy said "Let's catch him" which means "You climb up in the tree and grab him while I stay below and watch". (He is now the VP of a Bank/Credit Union so you can see where this is going.) I climbed up the tree till it was about an inch in diameter and leaned on a big Cypress too big for me to climb and the coon was at the tip and about the change trees so I yelled at my buddy I was going to shake him out and to grab him when he hit. I shook, the coon fell past me but without the support of the cypress my tree bent sharply and quickly and I tried to shinny down till "CRACK" the tree (and Me) fell out in the middle of the mud and cypress knees and the dogs who had returned. My buddy was chasing the coon but his light fell apart. I stood up in the pitch dark and leaned against the cypress tree for support and when I did I felt fur and grabbed it and caught the baby coon who was trying to escape again. He then squalled and I had all the dogs trying to climb up me, I finally got them kicked back, my buddy got his light back together, I took off my knee high rubber boots and took off a sock to roll the coon it (Socks and shirt sleeves make good catch bags if you don't have a corn sack) and we headed out.

........................

All I could hear in my head when I read this was "Knock him out JOHNNNN!"

WV Sawmiller · March 30, 2024, 06:16:54 PM

Ted,

I have 3 bundles of asphalt shingles I bought at a bargain at a local flea market. If you want to volunteer to lug them up that steep slope for me I will be glad to use them.

I get a back ache just thinking about carrying them up there.

Tom,

In my prime I'd have given John Eubankls a serious run for his money when it came to tree climbing.

I well remember climbing a big magnolia in the swamp behind my house with this same buddy along one day while looking for flying squirrels. About 50' up I stepped on a big dead limb that broke and must have weighed 40 lbs. I was up there hanging by one arm watching the limb headed straight for my buddy below knowing it was fixing to kill him. At the very last second he stepped back one step and it hit about 6" in front of his toes.

Don P · March 30, 2024, 07:34:44 PM

Here's where my mind goes, which I think will line up with the manufacturer specs, which is what you should be reading. I think they want 5v on a solid deck but either way moisture comes from the air in contact with metal that is below dew point

Why in the world would someone then say, let me pass more saturated air on the underside of said cold metal. That would cause sweat on the underside, which would then drip down.

Put the underside in direct contact with solid decking covered by tarpaper. First, there is no saturated air hitting the underside, no condensation. Any minor water is absorbed by the paper till the sun shines again, then vapor drive follows heat drive, the moisture is pushed to the underside on the sheathing where the ventilation should flow... if there is insulation this is its air channel under the sheathing as well.

moodnacreek · March 30, 2024, 08:29:48 PM

Quote from: Magicman on March 30, 2024, 01:50:58 PM
Quote from: moodnacreek on March 30, 2024, 01:03:09 PMScrew through the highs always. All my low screwed roofs leak after 15 years or so
My experience and recommendation is the exact opposite. Maybe it's the glaciated stuff up North??

My experience comes from several roofs on the barns and several here at the sawmill plus many others done by my son and customers. Over time the screws work up and cause a small leak and rot a little around the screw so you need a thicker screw. The damage done to the items stored like lumber; stained and full of ppb was or is completely unnecessary. This mistake has really cost me and it is not over yet.

WV Sawmiller · March 30, 2024, 09:39:17 PM

Sounds similar to my experience. The wind and heat and cold lift the metal and loosen it. Being over a solid roof on my shooting house should reduce the wind's effect. As mentioned always before I just had the metal attached to nailer/strips and the rest was open.

One tip I have used and really appreciate that came from Tom King IIRC was to use rivets to repair nail holes such as in used metal or if you miss a nailer. The good thing about the rivet is you can install them from above or below. From below it is easier to spot the light and where you can reach it from below you can seal it.

SawyerTed · March 30, 2024, 09:57:20 PM

Quote from: WV Sawmiller on March 30, 2024, 06:16:54 PMTed,

I have 3 bundles of asphalt shingles I bought at a bargain at a local flea market. If you want to volunteer to lug them up that steep slope for me I will be glad to use them.

I get a back ache just thinking about carrying them up there.

Piece of cake! It won't take but 25 shingles edge butted together.

If you can carry the poplar boards, 4 pieces of 24x96 metal roofing and all the tools, 25 shingles ain't nothing!

Of course I'm just a young man of 61! Driving to WV will be harder than carrying shingles!

Old Greenhorn · March 30, 2024, 10:10:19 PM

Quote from: WV Sawmiller on March 30, 2024, 06:16:54 PM....
Tom,

In my prime I'd have given John Eubankls a serious run for his money when it came to tree climbing.

I well remember climbing a big magnolia in the swamp behind my house with this same buddy along one day while looking for flying squirrels. About 50' up I stepped on a big dead limb that broke and must have weighed 40 lbs. I was up there hanging by one arm watching the limb headed straight for my buddy below knowing it was fixing to kill him. At the very last second he stepped back one step and it hit about 6" in front of his toes.

Just for the other folks not following what Howard and I are referring to in these side comments, because i (we) don't want to be rude, here is the story we are referring to:

moodnacreek · March 31, 2024, 09:20:27 AM

I have a recording of that.

RetiredTech · March 31, 2024, 12:55:39 PM

Quote from: moodnacreek on March 30, 2024, 01:03:09 PMPut any rough 1" boards close and black paper. Screw through the highs always. All my low screwed roofs leak after 15 years or so and walking on them is not fun with the purlin boards 2' on center.

I have to disagree with that too. I put the roof on my house in '95. We screwed it through the peaks beind careful not to strip the screws. That was a bad mistake. Within a few years I had screws baking out of the roof. I've had to tighten screws back down several times over the years and I'm always fighting small leaks around the screws. My advice would be to put down some felt or insulation sheet then strip on top of it with 1 by material and screw through the flat being careful not to over tighten the screws. Just tight enough so they start to bulge but not stick out from under the washer.

WV Sawmiller · March 31, 2024, 03:19:31 PM

RT,

I don't see how you are getting even small leaks if you installed the screws through the peaks?

RetiredTech · March 31, 2024, 05:23:18 PM

Unlike the old lead nails we used to use the screws will back themselves out. I don't know why. Another problem is years of being screwed down on the ridge the neoprene washer will deform and/or crack. They're made to be installed on the flat. That's a fact I did not know when I installed the roof. My roof has been nothing but trouble. It's a story and a half, I believe it is 6/12. That's been too long ago for me to remember. You can not stand or even sit on it. It's a pain to work on. On the other hand, my shed is a low pitch roof and was installed with the screws in the flat. I've only had two leaks in it. Probably from over tightening the screws. That's just my experience, YMMV. For me I'd never put in another 5v roof screwed through the ridge.

beenthere · March 31, 2024, 05:29:49 PM

On the flat or on the ridge.. is a catch 22. They both can and likely will leak at some point in time.

May just be that there is, and/or will be, some need for maintenance either way.

RetiredTech · March 31, 2024, 05:42:21 PM

Quote from: beenthere on March 31, 2024, 05:29:49 PMOn the flat or on the ridge.. is a catch 22. They both can and likely will leak at some point in time.

May just be that there is, and/or will be, some need for maintenance either way.

Agreed. The main reason I went with the 5v on strips was to hear the rain and not to have to replace shingles every 20-30 years. Well, I haven't had to replace a shingle and I still enjoy listening to the rain tinkling on the roof. Life is good!

At least until I have to scale the roof again.

SawyerTed · March 31, 2024, 05:45:03 PM

A manufacturer guide specifies 1 1/2" screws on peaks.

Any backing out of screws is probably due to heating and cooling, urethane caulk (can get colors to match roof panels) on the screw prior to installing will usually help screws stay in place if backing out is a problem. I've spent more than an hour or two adding caulk to new screws while refastening a metal roof to stop leaks. Backing out happens more with OSB sheathing.

The biggest DIY mistake is using an impact driver to drive the screws - they over drive screws/over compress washers. A screw gun is a better tool.

But hey, we use what we've got, right?

RetiredTech · March 31, 2024, 06:07:23 PM

That's interesting. I used silicone caulk on the screw threads the last few times I had to work it. I guess anything would be better than nothing. I can't say that I have had to redo any of the screws I've done that way. I also put a small dab around the base of the washer. I still think I'll screw though the flats from now on. Experience tells me it just seals better. I think you are 100% correct on the impact driver. A cordless drill with a properly set clutch is the way to go.