I'm about to put a metal roof over our existing shingle roof and have been told it is wise to lay 2x4s between them. That's a lot of 2x4s as the roof will take about 150 square of metal. I'm assuming you would do this to prevent moisture accumulation between the metal and shingles. First, is it necessary and second, if so can it be thinner than a 2x4.
I used1x4's.
i put them on right over the shingles. i have helped do serveral this way that are 10 years or older. no problems. some worry about moisture and the shingles wearing the metal from underneath but it hasnt been an issue. i would be more worried about the space between the shingles and metal being a home for rodents spiders and wasps. not to mention that hail can ruin a metal roof with the spacer boards in there.
it is imperative that you have good decking under the shingles and use screws that are long enough to reach it. pc
My folks had a metal roof put on their house recently. The contractor said the old shingles needed to be removed. I'm not sure what the reason was, but I know that there were at least two old layers.
I would use the cheapest boards you can find. Its true about the shingles wearing through the metal. If the metal is going to expand and contract a lot it will rub through quicker. Some days I can hear metal moving around quite a bit.
A trick to getting straight screw heads is to pre drill through a stack of roofing but measure carefully.
Don't use treated wood. It will eat the metal up.
For a longer lasting metal roof, the ventilation would be helpful. But who wants a roof that lasts a long time? ;)
I like a roof to last 30+ years myself.
In my neck of the woods most people that put metal roofs over asphalt shingles use ΒΌ" Styrofoam, commonly called fan fold, between the metal roofing and the shingles. The reasoning is that over time the sand on the shingles will cause the metal to wear out from the bottom side due to expansion and contraction. The Styrofoam allows the metal to move without the sandpaper effect, if you need additional insulation use thicker foam. :)
(https://forestryforum.com/gallery/albums/userpics/10034/wsroofsheetmetal20070601.JPG)
We had the same question and got all kinds of answers. We went ahead and put sheet metal right over the shingles using longer screws. It looks great after 4 years.
We roofed another couple more sections of roof this spring - again, right over the shingles. But we have one more major section of roof to do that has a long span. We will probably remove the shingles just to save weight.
They do make as special and pricy rubber sheet to put down under the metal. But we opted not to use it.
One tip I've learned to make the roof look better is to layout and pre-drill the screw hole before putting it on the roof. Leave them in a stack and that way the screw heads will all line up.
Quote from: Bibbyman on May 18, 2011, 04:14:39 PM
(https://forestryforum.com/gallery/albums/userpics/10034/wsroofsheetmetal20070601.JPG)
We had the same question and got all kinds of answers. We went ahead and put sheet metal right over the shingles using longer screws. It looks great after 4 years.
We roofed another couple more sections of roof this spring - again, right over the shingles. But we have one more major section of roof to do that has a long span. We will probably remove the shingles just to save weight.
They do make as special and pricy rubber sheet to put down under the metal. But we opted not to use it.
One tip I've learned to make the roof look better is to layout and pre-drill the screw hole before putting it on the roof. Leave them in a stack and that way the screw heads will all line up.
Going to agree with Bibby on this, I've done lots of metal over shingles. You don't need strapping as long as you the right mini-lags. As for the metal rubbing againts the shingles it's a myth if installed right. :)
Glad to see this topic, as I am goning to be in this boat pretty soon. So lets hear some more pros and cons...Tim
A builder friend of mine told me to lay down felt paper over the shingles so they can't make contact with the metal roofing, so that is what I did. However, after reading the responses to this thread and sitting here thinking about it, I don't think that was nessessary.
How much and how fast does the metal roofing move? I think it would take a very long time for the shingles to wear through the metal.
Thanks for all the input. I think I'll just lay it over the shingles. It doesn't make much sense that the shingles could wear through the metal, at least not in my lifetime.
KC your are two years older than me ...so I need more input... ;) Tim
I suppose it could be a regional issue, but the supplier where I buy most of the metal I use voids the warranty if it's placed directly over asphalt shingles. It also voids the warranty if you cut the metal with a saw. Five to ten years is only 10-20% of what is advertised to be a fifty year product. I guess time will tell who's right, but I will continue to use the foam not only over shingles, but under any metal roofing it also prevents condensation problems. :P
I used the Dow fan fold stuff on a shed. Great for new construction but I wouldn't use it on old. Put tin on the new house and pre-drilled all the holes on the ground. Made it lot easier putting the tin down.
Give these guys a call for a price.
http://www.gravettemetalsales.com/ They sell Central States tin. Good prices and good metal.
I am also getting a metal roof installed. The roofer is planning to put down 1x4 nailers over the singles. He said the air space helped cool the roof, and in Georgia, that is a big deal.
Quote from: Banjo picker on May 18, 2011, 07:40:23 PM
Glad to see this topic, as I am goning to be in this boat pretty soon. So lets hear some more pros and cons...Tim
The pros that the metal roof will last a very, very long time 8) The cons......if you don't like hearing the rain then don't install it :D
Quote from: WDH on May 18, 2011, 09:11:35 PM
I am also getting a metal roof installed. The roofer is planning to put down 1x4 nailers over the singles. He said the air space helped cool the roof, and in Georgia, that is a big deal.
Your roofer is right, it will keep things cooler with strapping, also keep in mind that the colour of the tin helps lots :)
Quote from: SamB on May 18, 2011, 08:41:50 PM
I suppose it could be a regional issue, but the supplier where I buy most of the metal I use voids the warranty if it's placed directly over asphalt shingles. It also voids the warranty if you cut the metal with a saw. Five to ten years is only 10-20% of what is advertised to be a fifty year product. I guess time will tell who's right, but I will continue to use the foam not only over shingles, but under any metal roofing it also prevents condensation problems. :P
So if you can't cut the tin what do they expect you to cut it with :D Take a skill]saw, turn the blade around and go for it 8) The noise will kill you but a perfect cut every time 8)
Quote from: cutterboy on May 18, 2011, 07:40:53 PM
A builder friend of mine told me to lay down felt paper over the shingles so they can't make contact with the metal roofing, so that is what I did. However, after reading the responses to this thread and sitting here thinking about it, I don't think that was nessessary.
How much and how fast does the metal roofing move? I think it would take a very long time for the shingles to wear through the metal.
The movement of the tin on the shingles is minimal, like if you think about it how can a tar based material with a few rocks go through metal over the years.
I've done it both ways. Be aware of weight, it can be a problem if you apply over the shingles. Metal roofing comes in 2 thicknesses. The thinner gauge needs a clean solid support, else walking on it will bend it. On my house, I removed the 2 layers of shingles, cleaned up the decking, and laid down 1 layer of tar paper, then the thin gauge metal. didn't pre-drill, used a battery powered drill driving hex head, self-tapping screws. I used long screws through the ridges, not down on the flat. If you do that, be careful not to over tighten the screws. That flattens out the ridge and messes up the sheet spacing.
Painted steel siding/roofing should be cut with snips or shears per manufactures instructions. Sawing with any type power saw heats the metal too much and causes premature oxidation. The same premature oxidation can occur when said material is placed directly over sand coated shingles and the underside of the material is compromised. Whether from expansion and contraction or simply being walked on. That being said, I guess it's up to the one paying the bill if they want to follow the manufacture's instructions and have a warranted product or not.
We had our medal roof installed 9 years ago. Its put down on the shingles. It doing just fine. The roofer had been installing metal this way for a long time up to this point. He said that there is a lot of untrue stories about the old shingles rubbing holes in the metal and moisture build up. But if anyone is unsure and can afford it then put what ever makes you feel more compfortable with under the metal. bg
A little clarification as to why I don't want to spend a lot of money putting this roof on. I picked up about 200 square of this metal roofing from an insurance company for a mere $600. It was supposedly hail damaged but I couldn't find one dimple in the whole mess. Basically it's in great shape, a little oxidation, but that's it. The holes are already there so I will have to use them. It's even the right color. If I can get 15 to 20 years out of it I will be happy.
:snowball: I'm living here in the great white north( :snowball: CANADA :snowball:) :D And was just wondering about how far apart do you place the 1x4's.For we get round about 3' to 4' of snow.Cause I was just wondering if a person has put stringers parallel with the rafters I know this over 120 days over on the comment,But I'm just wondering cause I'm tired of rain in the house also, :D .
Personally, I use 26 gauge roofing and 24" OC spacing for my 1X4 strips.
Quote from: Magicman on October 03, 2013, 08:00:57 AM
Personally, I use 26 gauge roofing and 24" OC spacing for my 1X4 strips.
Course you get a bit less snow in Mississippi than the OP does up in Canada.
Herb
Yup, my snow load is a mite less. :D
I just put some on my building. The guy at the lumber place said put the screws at 16 inches. He figured out the screw amount 16 inches on center.I put boards on the roof,no strips. I was undecided about steel or shingles.
I put metal on my 1000 sq/ft workshop over rolled roofing 8 years ago. I removed as much of the old R/R as i could but alot was stuck on really bad and time was of the essence (rainy season). I followed manufacturers directions and screwed next to ribs on the flat and using a 3/4 screw threw the ribs. I also used that rubber string and placed under each rib from top to bottom. All screws lined up and it came out great. With that many screws installed over good decking i cannot see that metal moving much at all. I used white to reduce heat in the shop.
As I type my son is having a metal roof installed over shingles .They layed down a layer of some type barrier to prevent deteriation from the shingles .
Kind of odd as I have something like 12,000 sq feet of new hidden seam 22 gauge lock seamed standing seam roofing material .He couldn't find anyone locally who knew how to install it .
As I have stated above, haven't had one problem with our roof as of today. It was installed over shingles in 2001. Thats about 12 years ago. bg
Which version of tin are you guys putting on, ridge and valley or free standing with hidden fasteners? I've been looking at tin on my house too, every time I ask I get a different answer and none are even close to being the same.
Ridge and valley with exposed screws. That free standing,standing seam is nice stuff. I would have it,but kinda pricey but 4 times as good as what I just used.
On the metal roofing with the exposed screws, you can get a pan head screw where the pan head completely covers over the little neoprene washer and compresses it just the right amount. The normal screws do not have a head that covers all the way over the washer, they just compresses it. The pan head type screws are a lot more expensive, but they are worth it because you will not have leaks in the future.
WDH,That's what I've been using,pan head screws.One inch,9 cents each,2 inch ones,14 each. The place that I brought the steel from calls them painted wood grip screws.
Anyone notice on some roof overs some of the screws back out after a few years?
I usually just screw it right over shingles unless roof is spongy feeling
Then I just use any one or two bys I have around
I did an old mobile home for someone ( it had the rounded roof ) I just made trusses from junk 2x4s
used old salvaged treated 2x6s from a deck I removed for something to hook trusses to
nailed old wood siding to them for something to screw the metal to that was over ten years back and it's ok
They still live in it
Ok guys, questions, on the free standing roofs, do they actually stay put and not leak with the hidden fasteners, everyone claims they do and one guy who actually makes the tin, rolls it onsite told them they will leak and will actually float and are not as nice, strong or durable as a ridge and valley tin, he's the only one to ever mention this to me, everyone else claims they are just as good as ridge and valley. On the ridge and valley tin, do you screw then on the ridge or in the valley, we used to nail on the ridge and have been having problems over time with them leaking, when we go to check it out, the tin has been moving enough to wear the hole larger and the nails are loose, so we've been screwing the tin on lately, seems to stay put better, but now we're considering screwing in the valley for new tin installation.
Next question, my house has an old slate roof on it now, any suggestions as to how to put a new tin roof on it? I figured we'd have to take all of the old slate shingles off and start completely over again, some say do nothing to the old base roof, just tin over it, and others claim I should put a membrane down, after taking off the old roof, and one guy told me he'd take off the old and just put tin on with nothing under it, seeing how we now have all options covered what's the right way to do it? I can't imagine leaving the old roof on, we'd break it up badly trying to tin over it and I thought it would be a disaster myself, but I don't want it to leak anywhere either and every tin roof on every shed I have has some leaks in it somewhere over time.
Onto the third question, the tin itself, we've torn down some old buildings that had the old style corrugated tin on it, both the 2.5 inch and also the one inch or inch and a half corrugation on it, we used it inside to line my shop so we just flipped it over and screwed it on upside down, it looks like new underneath and most think its new tin, but its heavy galvanized tin, about three or four times heavier than the new tin you can buy today, galvanized rusts over time and colored metal wears off over time, I have now two sheds that have no white color on at all left, my dad built the sheds back in the 80's and he's been having the galvanized shed roofs painted every few years for decades now, as of yet we've done nothing to the worn off white colored steel. Sorry this is getting long winded but does it make sense to just put a new galvanized roof on or go with a colored steel and let the color wear off over the years first, some tell me its the same tin, colored is just painted over the galvanizing and others say its completely different and galvanized is heavier on galvanized tin verses the painted style, any ideas as who's right, basically which will last longer before it starts to rust out and need painting??
I have re-roofed my house and a couple of barns. My experience may differ from others. I ripped off the old asphalt shingles because the were extremely old and brittle, plus the house had 2 layers of shingles. Put a layer of roofing felt down on the decking. Otherwise warm moist air against the bottom side of the cold metal will condense and eventually rot the decking. If you leave the old shingles in place, no problem. I used the ridge and valley type, ridges every 6 inches. Watch the way the edges of the sheets lap. The edges are different for a reason, and they lap right backwards from what you would think. The short edge goes on top. Never use nails to fasten any sheet metal roofing. Decades of experience shows the nails will eventually back out. Screws won't. The neoprene washers under the screw head are critical. Water tight seal, yes, but more important...The metal will expand with heat and shrink with cold. The soft washer will compress and expand as the temperature changes, rather than trying to pull the screws out. Don't over tighten the screws and flatten the washers. Do not pre-drill the holes for the screws. Use self drilling screws. About where to put the screws, I differ with most folks. The suppliers say use 1 inch screws and put them on the flat right beside the ridge. I think they say that because it does make the installation a good bit easier. My thinking is this. When, not if, the washers eventually come apart from age, you are definitely going to have leaks. By then, I'll be too old and decrepit to get up on the roof and fix the problems. I use 2 inch screws and put them through the top of the peaks, drilling through both layers of the laps. Here, over tightening will cause another problem. It will flatten the peaks and mess up the alignment between sheets.
Another observation.. I have an old broiler house/shed that I use for lumber storage. Roofed with used corrugated metal. there's LOTS of extra holes. Stand inside and look up and you can see sunlight in dozens of places. the holes are all on the top of the peaks. Don't leak a drop...
Here in Indiana, I can literally hear my lean to roofs on the barn expand and contract as the sun comes out in the morning and goes behind clouds. With this, I believe them when they say put something over the shingles. It isn't so much that the metal expands and contracts enough to wear through, it is it does it enough to scratch and cause rust then it is like a chevy pickup in the '70's, rust through quickly! I also was taught on roofs to put the screws on top of the ridge, on walls on the flats. But to each their own.
I always put the screws on the ridges also.
Put up a quick screened porch once dew collected inside and dripped
Ended up removing metal and used osb and layer of felt under metal
Where do you get pan head screws from, I've never seem them anywhere, nor heard of them.
I got mine from a small lumber yard in town. I know the big box stores has them too.
This should do it for ya
http://www.metalsales.us.com/files/installation-guides/Application%20Manual-West%20Coast.pdf
Page 25,Fasteners
This where the steel that I just brought came from.
i have put tin 29gauge on my cabin up north and on the house i live in.on this house some pieces are 24 feet long ,one piece.i put the screws on the ridge which the tin supplier and i disagree about each time i see him.one thing of note ,tear off the old dripcap and put new drip on on top off shingles.do not be in a hurry and slap the tin on without fixing the drip cap.right now galv is 1.60 alineal foot,wite is 1.90 a lineal foot.both 36 inches wide,29 gauge.brand new no. 1 tin .around here we call this pole barn tin.
Here is an example of what I called a "pan head" screw. Probably not the right term, but the picture shows you how the screw head will cover over the washer, not just compress it.
http://www.levisnailsandscrews.com/proZ.php
I don't know the name of the roofing screw, but it is not a "pan head" screw. Pan head screws have a rather large flat head. LINK (http://www.dkhardware.com/product-43160-sbp1420x134ps-1-4-20-x-1-3-4-pan-head-slotted-machine-screw.html?mr:trackingCode=93E3F610-CDE0-E111-9B44-001B21BCB944&mr:referralID=NA&mr:adType=pla&mr:ad=18074698332&mr:keyword=&mr:match=&mr:filter=60257256252&gclid=CLrAvqbT_7kCFUhk7AodxU4AIg) They can be either slotted or Phillips.
We've been using the screws from either menards or home depot, does anyone know what those are considered, good or bad? Or have a comparison of those to what your referring.
I doubt that there is any appreciable difference between manufacturers of the roofing screws that WDH posted. They are actually designed to be used on the flats rather than the ridges of the roofing.
I brought some steel from Home depot years ago and than some from that link I posted.I had some screws left over from Home Depot, I looked at the link that WDH and thay all look just about the same. The link that WDH put in,the part below the head does look more like a pan. If you go to the left of his link where it says to browse screws,those are more like the ones that I have been using.
Here's what I have been using.
(https://forestryforum.com/gallery/albums/userpics/10436/thecfarmroofscrews2013.JPG)
The 2 on the left are from Home Depot, years ago. The washers can be easily removed from the screw.
The 2 greens ones on the right are from the steel place. The washers are thinner,but are not easily removed from the screw.
And I brought the steel from a local lumber yard,delivered free, and I was in one of the big box stores and checked out thier prices. I have no idea about the steel panels,but the ridge caps was about $12 more and the edge trim for the trimboards was about $8 and the so called flashing pieces was about $8 more too. The stuff looked exactly the same thing as what I have.
Go with the hex head screws, a phillips head will collect water in the recess. Use a socket in a drill that has adjustable torque. Most suppliers will stock a 1/4 inch socket with a short shaft that fits in the drill chuck.
Make sure it's magnetic too.
We've been using a cordless impact driver made by rigid bought at home depot, slickest thing I've ever found to install screws of any configuration into anything. It'll torque things down gently and can stop in an instant as its torquing down, turns fairly slow which is a plus compared to any drill.
If these screws are meant for valley installation, what's the best for ridge installing screws? Is there any major difference other than the length?
I was taught to put the screws on the ridges on the roof and on the flats on the walls. More water runs on the flats on a roof and putting the screw on the ridge reduces leaks.
If your screws have the rubber seal on them, they should be drilled on the flat of the roof.
Screws with out rubber seals go on the ridge.
99% of the roofing today is installed with the screws with rubber washers. Just make sure your screw makes a flat fit.
Note: The reason 2x4's were recommended was that the screws will not back out over time. Using 1x4's will not give the screw enough meat to hold on to over time. So if your running your screws into a shingles roof and on into the plywood under the shingles....watch for your screws to back out over time.
The screws that I have shown can be used on the ridges or the flat part,The links shows it.
Postonlt40hd, why would one put screws on the roof in the ridge without any washers on them, what keeps them from leaking then or keeping the tin from wiggling, I was always told the washers held out water and also kept a snug fit on the metal, I have no idea if its true or not.
Sorry Randy, I honestly did not mean it like it sounds. My Dad built a barn back in the '60's. Screws and nails for roofing did not have washers on them then.
That is why they were installed on the ridge so the water would shed away from where the screw/nail went in.
I did not mean to be confusing.
I think most of the nails and screws now have the rubber washers like the ones in the pic that Thecfarm showed.
Back in the 50's they used lead head nails, then went to nails with rubber
washers for metal roofing
Quote from: Kcwoodbutcher on May 18, 2011, 12:34:19 PM
I'm about to put a metal roof over our existing shingle roof and have been told it is wise to lay 2x4s between them. That's a lot of 2x4s as the roof will take about 150 square of metal. I'm assuming you would do this to prevent moisture accumulation between the metal and shingles. First, is it necessary and second, if so can it be thinner than a 2x4.
I just put a metal roof on my home and layed it right on the shingles. no problem thats the way its done here in my area southern illinois later
More than one way to skin a cat, they say, 1x4's, chalk line and square the ends, makes for easy installation, they way it's done here, yes its allot of lumber, but then again its a roof. david
Quote from: cutterboy on May 18, 2011, 07:40:53 PM
A
How much and how fast does the metal roofing move? I think it would take a very long time for the shingles to wear through the metal.
Doing the math, a 100c temp change on a 30ft long steel piece will change by 0.612".
The speed of change is proportional to the change in temperature.
Typical roof won't see quite that temp raise, unless you live in the SE desert.
When you install metal roofing over shingles it is hard to snug up the screws without deforming the tin.If the screw happens to fall by the bottom edge of the shingle and is tighteneddown it will wrinkle the tin.
Putting screws on the ridges in the tin can cause the sheets to grow in width if the ridge gets compressed. A 36" wide piece of roofing starts out as a 42" flat sheet before it is formed. A trick used by some roofers to make the tin fit an out of square roof is to step on the ridges causing the sheet to become just a little wider. It is amazing how much you can gain over the width of the roof.
Quote from: POSTONLT40HD on October 05, 2013, 03:17:52 PM
Note: The reason 2x4's were recommended was that the screws will not back out over time. Using 1x4's will not give the screw enough meat to hold on to over time. So if your running your screws into a shingles roof and on into the plywood under the shingles....watch for your screws to back out over time.
Exploring this topic further, screws come in different sizes. Typical is the #9 or 10 used 90% of the time. Great for new construction into 2 X lumber. Bigger screws can be had in #12 size to replace screws that failed to hold and really big #14's are made to use in plywood and OSB. Of course the bigger the screw the larger the expense. And when that little bitty screw backs out of an existing OSB roof or 1 X 4 stripping it really gets expensive.
I have time to do it right, I don;t have time to do it twice comes to mind. strip the roof lay 90lb felt, , put the tin down. like putting new shingles over old ,my dad said do it right or not at all.
best of luck your way :)