metal roofing

[Thehardway]

Guys,  thought you all could provide some insight on this.  I would like to put some kind of metal roofing on my house and am getting ready to order it.  I will be placing 8" SIPs over my timber frame roof trusses.  On top of that I want to put the metal roof.

Can't make up my mind on the type of metal.   There will be an addition to this house a few years down the road so I am leery of using a painted metal and trying to match color later.  Thinking about just using a corrugated or ribbed, mill finish galvalume.

Here are my questions:

1. What weight of metal is sufficient.  Local supplier sells 29ga. It seems pretty thin.

2. Is  felt paper over the SIP sufficient or do I need to strap, most of the metal suppliers want it fastened direct to solid deck,

3. Do I need to worry about heat or moisture/condensation buildup. Have read different things and none of the "experts" seem to agree.  How hot does a mill finish get. I know it reflects most heat.

4. Should I block airflow under the metal or encourage it.

5. has anyone ever used a double bubble foil for this application.  Seems like it might be a good solution.

Air leakage from the inside should be minimal as there are very few seams/penetrations and I will make sure I seal all the joints well.  I will use an ERV to control inside humidity.  Maybe some of you have this on one of your homes or outbuildings and could give me some experiential info.

[Stephen1]

I have 8in. sips on my cabin also.
I was told by the metal suppliers to strap 1st, to provide ventilation over the sips. I strapped cross ways with 2x3. The gentlemen selling me the steel has found problems with steel & sips from no strapping. There will be condesation under the steel. It was also recommended to use Tyvek wrap, not felt, I cheaped out and used house wrap, no problems so far, I believe there is a roofing material made by Tyvek and others, I just did not have the money at the time and the house wrap seemed like a good alternative.
If I had the money I would use standing seam steel roofing.
my steel is 26gauge but we have snow to content with, I can still see the faint impressions of my son as he stood on the steel to install it. 24 might have been better.
I encourage the airflow, I strapped up & down then across allows the air flow up from the eves, which has brillow pad material to keep the insects out and allows the air in

[Thehardway]

Stephen,

Do you have an interior vapor barrier installed? How are the seams of your SIPS sealed.  Is the condensation from warm are leaking from the house in winter or is it during summer months.  What color is your roof?  Sorry for so many ?'s

[zopi]

I don't know how pertinent it is to what you are doing...but our house has a standing seam steel roof, and the attic is totally unvented...the roof itself is 130 years old..I went up there after we bought the house and it was kind of like stepping back in time...the house was originally built in 1820, and half burned during the civil war....was rebuilt in 1876...they reused some of the boards from the original house and left the charring in place...those charred places look like they were burned yesterday...

The insurance company had a fit when we told them how old the roof is...I may never have another
asFault roof...

gotta roll the sucker out next summer though..

[Stephen1]

Stephen,

Do you have an interior vapor barrier installed? How are the seams of your SIPS sealed.  Is the condensation from warm are leaking from the house in winter or is it during summer months.  What color is your roof?  Sorry for so many ?'s

there is no vapor barrier, the sips provide it, my joint of the sips are all foamed together.
The condensation is naturally formed on the underside of the steel, warm and cold, has something to do with the dew point, I don't know how to explain it, someone here might have a better understanding,
The Tyvek is to prevent that moisture, from running down the OSB of the sips.

[FrankLad]

I was also informed by our panel company (General Panel) that the SIPs provide the vapor barrier, but that felt paper wouldn't hurt anything.  So we went ahead and put felt paper for added protection from rain (because we knew it would be a while before we got the metal on).

We strapped it out with 2x4s which were fastened down with 3" screws.

The SIPs are all joined (company-provided glue/sealant and nails) with 2x6 spline material.

[submarinesailor]

Hey HardHead... Oh I mean Hardway,

Up in Syria, VA. I use a product that I order from the local COOP that is rolled out over in Orange.  At the Union Metal plant – I tried to order from them but they would only sell to dealers (wholesale).  I use their MasterRib in the 26 gage.  Tried the 29 gage and hate it so much that I will be replacing it this week end – I hope if the "Honey-do's" don't get in the way again.......

If you look at their installation manual, http://www.unioncorrugating.com/documents/MRInstallationManual_4-07.pdf, they have moisture barriers under everything.

Bruce

[Thehardway]

Subman,

Thanks, you confirmed my suspicion about the 29ga.  looked like it would wrinkle real easy.  I will opt for a 26 or 24ga.  The installation doc. Union has is very comprehensive, one of the best I have seen but it still does not have any specific guidelines for SIP installation.  It lumps everything together as "substrate" as best as I can tell and says "according to local code" for moisture barrier.

It seems like the steel manufacturers and the SIP manufacturers want to be as vague as possible to protect from possible warranty claims.  I have no problem installing a moisture barrier, I just don't know of a local code that adresses steel over an unventilated roof system.  I don't want to trap moisture in the wrong place.  I am still doing some research on this one.

What if I install a standard 26ga. corrugated metal with 1/4" high corrugation and install a double bubble vapor barrier under it without strapping?  This would eliminate most of the air under the steel which should eliminate just about all condensation.  Any that did form would be unable to get to the SIP and would simple run down the metal or plastic to the eave or evaporate out the ridge.

BTW I am a 'hardhead".

[Stephen1]

Check out the Tyvek roofing material, from what I was told it seals around the screws. It seems that you like that bubble wrap, you must have a few rolls laying around ;D  Your idea sounds good, or will the moisture get caught in the wrap as it try's to run down the roof. What is your roof pitch?

[scsmith42]

If you use the bubble insulation underneath the tin, it should act as a thermal break and reduce heat transfer from the metal to your SIPs.  You might see a sligh increase in efficiency in the summer.

Bob - I've installed several tin roofs in the past couple of years, and if you're interested I will be glad to share some tips on how you can ensure that your edges all align properly. 

One thing that really improves the craftsmanship (unless you're using standing seam) is to mark and pre-drill your holes.  This provides a clean, neat alignment of the screw heads that can be viewed from the ground.

Scott

[pineywoods]

I re-roofed my house with the thin 29 gauge, but it was laid down over solid 1X8 pine decking. Used tar paper vapor barrier. worked just fine.

[Thehardway]

Scott,

You hit the nail on the head with my bubble foil idea. Unfortunately I don't have any laying around but I was thinking radiant/insulative barrier to protect the SIP from heat off the metal and at the same time provide a vapor barrier for any condensate.  It adds no additional height to the roof like strapping would.  My roof will already appear quite thick.  It should also dampen noise.  Good advice on the pre-drill.  Did you do it while they were stacked?

I have seen docs that show screws in the low spots, crews in the high spots, "stitching" screws at the seems, where did you drill your holes.  I always thought they went in the highest spot.  Did you use rubber gasket screws or just plain galv. screws?

[Raider Bill]

Bob,

I used 30lb felt directly on my osb, time will tell...............

I always thought you screwed on the high spots but was told to do it on the low which I did with rubber gasket screws. .26 ga

[pineywoods]

By all means use the screws with the neoprene washers. On the flats versus ridge question. Roofers and suppliers say down on the flats, I put mine on the ridge. My take was this, the rubber washers will age and deteriorate, on the flat, you will eventually get leaks. By then I'll be too old and decrepit to get up there to fix it. There's one gotcha to putting the screws on the ridges...DON"T OVER TIGHTEN. That spreads the ridge and widens the  sheet. Messes up the alignment between sheets. Pre-drilling....I don't. I just put one or two screws per sheet up at the very top down on the flat where the ridge cap will cover them, then snap a chalk line across the whole roof to get nice even screw spacing. Pay attention to how the sheets lap. The edges are not the same and they go right backwards from what you would think...

[moonhill]

As pineywoods says, pay attention to the direction the sheets go.  If pre-drilling split the stack in half and orientate them for proper sides of the roof.  I have placed the screws on the flats and the ridge.  Warrantee issues may be a problem on the ridge.  Check with the manufacturer for proper directions if it is important to you.  I like a harness and snickers for traction.  Aluminum ladders with a roof hook can scratch the finish, pad them well.  My last roof came with a new improved screw, it has a cap over the rubber washer covering it form the sun.   The cap is the same moulded piece as the hex head, a great improvement.  They are also easy to tighten down to the proper amount, if you go too far the cap contacts the roof.  No more worrying about the washer bulging out.  I like the screw down roofing, as it is less expensive and no special tools for crimping.  It can be replaced with ease if the building needs additions added at any time. 

Tim

[Thehardway]

Wow, lot's of good info.

Tim,  what was the name of those new screws you used.   The manufacturer's recommendation for the corrugated panel is to go through the higher ridge if using nails and if using screws go though the lower part (flats). The point piney makes about spreading when going through the ridge is a good one.

This roof is a 12/12 pitch.  Water should run off pretty good even if each screw doesn't seal perfect but I like the idea of the neoprene being protected against UV exposure and from distorting by over tightening

[PineNut]

I agree with using the cup head screw. They were not available for most of my roof work but were used on the latest. They cost more but are well worth the additional cost. I don't know the name of them either.

[scsmith42]

That's a good idea re the radiant insulative barrier; as I recall that stuff is pretty thin.

Ditto Pineywood's comments.

I too prefer to screw on the ridge, as opposed to the flats, for the reasons already stated.  The screws that I use have cupped washers on them above the neoprene.

RE pre-drilling, I will divide my tin into two stacks - one for each side of the roof, and remove two sheets from the stack (each end piece).  The rest of the sheets are aligned on the bottom end, and I measure, center punch, and then drill the entire stack.  Once I'm done, I'll use the template sheet (top one) to pre-drill the other two sheets, doing the middle row on both and one or the other outer row (depending upon which end of the roof it's one).  The outer holes for the end sheets are drilled up in the air, as that way I can make allowances for any slight variances in the eave width.

Many of the roofs that I've done are a steep pitch, and if I pre-drill them and use skip sheathing (which allows me to easily stand on the roof) I can install all of the screws as I go.

The neatest trick that I've found has to do with aligning the tin.  I have a CST Berger laser level that has a rotating beam with a center beam that goes straight up.  This laser is also designed to operate working on it's side (it's self leveling). 

On roofs, I'll measure around 38" in from where I want the outside of my panel to go, and nail a board in-between two of the trusses at the ridge.  The laser is then set up horizontally on the board, centered over the ridge, with the straight beam shooting down the ridge of the roof.  The laser is adjusted until the beam is directly above the center of the truss on the opposite side of the roof.

Since the laser is rotating, the side lobes are flashing across the skip sheating, all the way up and down both sides of the roof.  I'll place a reference mark on the skip sheathing at the ridge, at the bottom, and in the middle.  I'll use these lines as measuing points to the tin.  Since my sheets are 36" wide, and my reference lines are 38" in from the outer portion of the roof, I'll align the first sheets so that the edge is 2' from the reference lines.

I'll measure from the reference lines all the way across the roof, marking every 9 feet.  Thus, every 3 sheets of tin I have a reference line that I can check to see if my alignment is straight.  Sometimes I'll need to shift a piece of tin 1/16 or thereabouts, but this method provides for precise alignment all the way across the roof, with clean bottom edges.

[Joel Eisner]

Okay ... Bob .... for those of us with a day job off the farm (sorry Scott), I would do the following:

1. Not pre drill the screw holes because there are always the few holes you will mill when placing the screws.  Not all of us have a fully actuated lift that will allow us to check the allignment of the screws in the future

2. Screw in the flats, especially if the manufacturer calls for it

3. Have the manufacturer provide the color matched screws with washers and neoprene.

4. If using multirib make sure that you use a closure strip since lots of creatures like to hide under the roof (I know first hand).

5. Sound from rain will not be a real problem with the SIPs.

6. Regarding the gauge of the tin, don't worry about spending a lot of money on the heavier ga since you are not going to be spanning skip sheathing. Regardless of gauge, things dropped from above like entire windows (don't ask how I know this) will leave marks.

7. Keep a tube of 100% silicone silver caulk with you and use it if you have any issues or concerns

[Dana]

Check on the warranty of galvanized vs painted. I was surprised, when I checked that the company I looked at, had a better warrant on painted than galvanized.

[Larry]

My thoughts on metal...

29 gauge is meant to span 2' while 26 gauge is for 4' spans.  In this area 26 gauge is almost always used on boat docks and commercial work because of purlin spacing.  29 gauge is for residential because were not dealing with any span in most cases, and at most 2 foot.

Screws on the flat...to tight and the washer squishes out allowing UV to detoriate it...leaks later.  To loose or cockeyed a leak.  Just right and good forever.  And there is a difference in screws.  On the ridge...some say thermal metal movement causes the screw to loosen.  Suppose its your choice but I've went with the manufactures recommendation.  I'm going to investigate the screw caps...never heard of them but they seem like a good idea.

Pre-drilling is the only way to go.  Besides the esthetics it also lessens the chance of metal chips causing a tiny rust spot.

Sheet alignment...most times a roof is seen much more from one gable end than the other.  Start your sheets on the off side from the most visible gable.  If you don't in some light conditions you can make out every sheet.  If done properly the roof looks like one solid sheet of metal.  Hope I am clear what I'm trying to explain.

I've thought about bubble wrap under the metal...sorta of expensive.  I have used Dow Blue-Cor which is 1/4" thick styrofoam.  It worked fine but I don't have any strong feelings about the use.

Scott, I just learned how to trim rafter tails with the laser couple of weeks ago.  Thanks for the explanation on how to get tin started using it.  Sheet alignment can be adjusted if you get off by starting screws on the far side of the sheet and working back towards the sheet already in place.  Just do it on one end.

"Cool Metal" Almost everybody is selling it and even in dark colors.  I've heard explanations over my head...special paint, light wave lengths, and maybe a little voodoo.  Anybody have thoughts?  Some places are charging quite a bit more for that special paint.  I'm close to buying some metal and would like to get the most bang for my buck.

[routestep]

Hardway,
I just put corregated sheet on a small workshed my brother and I built. The screws we used have on the green box   Hillman The Fastener Center. The heads use 1/4 inch hex with a neoprene washer. We used an electric drill and since we put the screws in on the ridge we hand tighten them down the last turn or so.  I can't remeber if we got the steel and screws at Loews or The Home Depot. It all went very fast, but then it was a 4 in 12 pitch roof and a 12' by 16' shed.

[woody1]

We sell abc metal roofing. It is a good product, we sell 90% 29 ga. imperial rib.We have had very few complaints, mostly customer handling. I think they have a plant in VA. www.abcmetalroofing.com
Woody

[Jim_Rogers]

I put some metal roofing on a sawmill shed roof once, and I was concerned about where to place the screw, in the flat or on the rib.
To me in the flat didn't make much sense, so I put it on the top of the rib holding two sheets together on the edges.
However, as mentioned it forced the sheet down and this wasn't good, again as mentioned above.
So what I did, having a sawmill handy, was cut some strips of wood and place them vertically from eave to ridge for the rib of the metal roof to sit on. These strips took up the gap between and when the screw was fastened down the sheet didn't squeeze down.
Using my battery powered portable screw gun, I could set the clutch to stop tightening at the right amount of pressure to not squeeze the rubber washer out very much......
Just my way of doing it....

It added some work adding the strips from eave to ridge but the sheets dropped in very nice....
Strips were added using a nail gun.....

Jim Rogers