tin over shingles ???

[1jjpop]

I have been watching people overlaying a shingle roofs with tin , one guy laid the tin over the shingles & nailed thru the old shingles into plywood sheeting another guy nailed 1'' x4'' strips of wood across the roof every 2' Then placed tin on the roof & nailed to 1x4's . Which is best ? By putting strips on you may get some ventilation ??

 

[Boilerhouse]

I asked a roofer about that when I redid my roof in 2014. His advise was strap every 2 ft then tin - so I did. To be honest, despite the fact I had zero time to squeeze this job in, I wish I had removed the old shingles first. I dunno - just think that is the right way to do it.

 

[lugnut71]

I see it all the time, I personally would remove them , to me its like sweeping dirt under the rug.

 

[rlitman]

I wonder what the difference in noise would be. Tin isn't all that quiet in the rain (let alone hail).

 

[77thor]

...I personally would remove them , to me its like sweeping dirt under the rug.

^^^ This.

 

[blair683]

Remove them! When you put the tin directly on the shingles it will scratch the **** out of the back of the tin and rust through. I’ve heard of people putting the strips first and the shingles would rot under the tin. I’ve read where people said their shingles would rot to the point that you could smell them. Also you say nail the tin down but am guessing you mean screw with the rubber washer. Back in the day they would actually nail it on old barns. The right way is to remove the shingles. It doesn’t cost much more but maybe 3 hours of labor. Not to mention that you don’t get to see the condition of your roof decking without removing the shingles. The roofers that throw it on top of the shingles are hacks just trying to make a quick buck (that’s my opinion).

I forgot to mention. Look at the metal manufacturer install instructions. I guarantee they want you to use synthetic underpayment with ice and water guard. I bet leaving the shingles voids the warranty on the metal as well. Most will even tell you where to screw (it’s not on the rib either).

 

[Kaizen]

Definitely remove. Too much money for new metal to half *** the job


Sent from my iPhone using Tapatalk

 

[NUTTSGT]

Put me in the remove crowd also.

When we did a friends roof with rotten decking, we took the shingles off along the 4x8 sheets of roofing and replaced the sheathing then put down synthetic underlayment.

 

[850xpeps]

Remove the shingles. It’s a half assed way to leave them. My tin is set down right on my 1x6 roof sheathing. No noise at all from rain or hail because it can’t bounce. If you install it on strapping it will be noisy.

 

[ford33]

Remove the shingles. They will rot under the heat and humidity of the tin roof. You may get mold or algae growing under the tin.

 

[KevinL]

I had a steel roof done on my house 10 years ago. They screwed down 2x4's, cut out the peak and screwed down the roof panels and put a continuous vent on the peak.

I have a 4/12 pitch roof. The one thing that I didn't consider was the rain gutter. I had to go with a 6" gutter and put leaf gaurd so that snow wouldn't take the gutter off. If I could have went with 5" gutter I could have done the entire house and garage for $1100. Only one person here in North Iowa does 6". It cost me $ 3000 for the 6" with leaf gaurd and it works great.

It makes no more noise than my old roof. Neighbor has the same thing and they love it as well.

 

[alwaysFlOoReD]

Where is the moisture coming from to rot the shingles???? Unless you screwed up on ventilation or improperly applied the steel there is no way for moisture to be present.

 

[blair683]

In this thread you will be able to pick out the guys who have steel over shingles. There is no excuse for it other than trying to cut corners.

 

[firebirdparts]

I don't know about the shingles, but furring strips ought to allow the roof to be a really good radiation barrier, which overall I think is a plus.

 

[WausauDug]

1jjpop, garage or barn ? Metal roofing expand/contracts w/ the sun and wears whatever below and and over time can make you wet! In many situations fanfold insulation handles that wear and gives you the cushion just fine. Takes some time to knock down the curled if bad and then fanfold takes care of it

 

[ZipSnafu]

Where is the moisture coming from to rot the shingles???? Unless you screwed up on ventilation or improperly applied the steel there is no way for moisture to be present.

Condensation??? I am by no means a roofer type of person but that would be my guess.

 

[johninct]

Remove them!!! Don't forget, tin weighs something too.

 

[tapered-pin]

remove them, but not for any of the reasons given to you, remove them because of the differential in thermal expansion between the two materials.

tin leaks over time because it's typically face nailed through to wood (rigid connection) and the tin moves in the direction of the long axis of each piece when heated/cooled, so you essentially have a nail that "rips" a hole in the tin, as the tin moves under it..
OR
if your fasteners are far enough away from each other, the tin will buckle, causing an audible indication and potentially separate from the adjacent piece of roofing, causing a point of water infiltration.

standing seam doesn't do this because it's traditionally installed with concealed clips which will move within the seam and allow the roof to move independent of it's substrate (sheathing)

 

[jjgrappler]

Here's what I was told when I had my metal roof done 2 years ago. First contractor wanted to put them over my shingles, 2nd contractor quoted me a little more than the first guy but removed all the shingles. His explanation to me was as the shingles deteriorate they break down and could loosen the screws on the metal roofing causing them to become loose. I went with the 2nd contractor. I am glad I did because when they pulled up my shingles I had a bunch of rotted boards that need replaced and they did it. I agree with the other people, its laziness and cutting corners, also possibly could be hiding a problem hidden under the shingles.

 

[NUTTSGT]

If you roof could talk, it would thank you if you take the shingles off. Do you realize how weight you're taking off the trusses ?

 

[Schurkey]

Tin??? Really?

 

[NUTTSGT]

Tin??? Really?

Yes..

 

[TractorJeff]

All my roofs are "tin". House was done before I bought it. They left the shingles on and laid furring strips. Nails are working up now after 20 or 25 years. I go up there in a basket and pull them out. Then drive longer screws in the same holes. 1/3 is done, need to get the basket again when the wind is warmer!
My shop and Garage roofs are tin that I put down after stripping off 2 layers of shingles and 1 layers of wooden shingles.
For what its worth "tin" is lighter than shingles!

 

[6768rogues]

Asphalt shingles weigh between 2 and 3 lbs. per square foot. That weight is almost negligible over trusses.

 

[TractorJeff]

LOL!
Maybe they are only 2 to 3lbs/ft till you are carrying them up a ladder!

 

[Schurkey]

Tin??? Really?

Yes..

What's the point of misrepresenting sheet steel as "tin". Might as well call it Magnesium, or Titanium, or Kryptonite. Any of those names would be just as incorrect.

It ain't tin.

 

[like2wheel]

Glad you cleared that up.
I'm sure everyone here was confused .


So from now on it has to be "cat on a hot sheet steel roof".
great...

 

[NUTTSGT]

Asphalt shingles weigh between 2 and 3 lbs. per square foot. That weight is almost negligible over trusses.

Per square foot maybe but when you start adding up the weight of those shingles across the entire roof, possibly maybe even having a second layer or worse, a third layer it becomes alot.

Take into account if it's an area that gets a heavy snow load during the winter. That extra weight could just very well be the straw that broke the camel's back with an exceptionally heavy snow fall.

My point, why make the trusses carry the extra weight ?

A 30x40 will need about 14 square to cover the roof. At 3 bundles/Sq = 42 bundles. A bundle of *dimensionals weighs 72 lbs. 42 of them will weigh 3024lbs. That's a ton and a half.



* Owens Corning Oakridge as an example

 

[NUTTSGT]

What's the point of misrepresenting sheet steel as "tin". Might as well call it Magnesium, or Titanium, or Kryptonite. Any of those names would be just as incorrect.

It ain't tin.

I know it's not tin, merely a joking reply to your post. I suppose you didn't watch MTV in the eighties and had to watch the B52s sing "Love Shack" every morning ?


It's more of a regional thing calling it tin. Even though it's steel, some of the older crowd still call it tin. . . . like calling a Coke, pop, soda or drank.

 

[redneckcharlie]

Do the math, even two layers and metal dont weigh squat when spread out over an entire roof. Even two layers of dimensional material is a little over 5lbs/ft. All of this comes down to if someone wants to pay the additional labor to remove the existing material or not. Metal roofing here with traditional screws will start backing the screws out due to expansion and contraction regardless of shingles being present under the metal or not. Standing seam is the only type of metal well do because of the above.

Per square foot maybe but when you start adding up the weight of those shingles across the entire roof, possibly maybe even having a second layer or worse, a third layer it becomes alot.

Take into account if it's an area that gets a heavy snow load during the winter. That extra weight could just very well be the straw that broke the camel's back with an exceptionally heavy snow fall.

My point, why make the trusses carry the extra weight ?

A 30x40 will need about 14 square to cover the roof. At 3 bundles/Sq = 42 bundles. A bundle of *dimensionals weighs 72 lbs. 42 of them will weigh 3024lbs. That's a ton and a half.



* Owens Corning Oakridge as an example

 

[willymakeit]

Tin comes from a different era. Tin is part zinc which on a sunny day builds a lot of heat behind the panels think 160 Fahrenheit.
We still see the occasional zinc coats for exteriors. Plays havoc with a lot of envolope materials

 

[1jjpop]

They were both houses I seen them do..

 

[tapered-pin]

We still see the occasional zinc coats for exteriors. Plays havoc with a lot of envelope materials

?

galvanizing is EVERYWHERE..

mainly because of it's weather resistance over time.

chain link fence
DOT railings
handrails
deck fasteners
roof panels
it's literally everywhere.

 

[Jazz1]

we tin right on top of shingles 20 years ago. Also did 6 more cabins on the river same way. No strapping, no issues

 

[billspit]

I see it all the time, I personally would remove them , to me its like sweeping dirt under the rug.

I feel the same way. My OCD would not let me do that. Its like when I see people putting vinyl over half rotten siding and fascia. It looks great after they finish, but you know what is underneath. There are several small houses I pass regularly that they did that to.

 

[Falcon67]

Lots of "tin" roofs here, it pretty popular even though it seems to run 50% more $ to install. I'll ask my ex SIL but I think it's either way - some leave the shingles, some strip and use a modern underlayment. Personally I'd like to see a tear off, check for damage and repair any decking, then a modern synthetic underlayment with the metal right on the deck.

 

[LS6 Tommy]

I'd do the tear off. Actually, I don't think I have any other option. I seem to recall being told that NJ no longer allows reroofing (second layer on a roof)...

Tommy

 

[gotwheels]

I would think you and your insurance company would have risk management concern of fire. I have seen the difficulty of extinguishing a fire with asphalt shingles under a metal roof. The fire keeps rekindling as the shingles hold heat and are a fuel source. I think the other expressed concerns of roof loading and less stable installation are valid as well.

 

[Tejay]

I’m sure I could install hardwood over carpet also and it would look fine. Just remove the shingles - it’s not that big of a deal and you then can make sure your roof is solid.

 

[toolmiser]

Something to consider with a "metal" roof. I was thinking of one a few years ago and the sales person mentioned that I wouldn't be able to walk on it for safety reasons because they are slick. I have a "hip roof" two story house with established trees all around, and gutters. It would take forever to clean the gutters off of a ladder. Am not sold on gutter guards, so went with asphalt.