Pro's/Con's of Metal Roofing?

[tjm73]

Metal roofing vs. traditional shingles?  Help me educate myself.  Seems like everything I try to learn about, info is had to locate.

[glenn-k]

I and my crews have done about 300 metal roofs on steel buildings.  Same material - different fasteners.

My mom and  dad put it on their old house and are happy with it.  

The big sheets cover quickly.  There are some companies that specialize in providing sheeting for home re-roof jobs as well as new.

It looks like a metal roof - that can be a plus or a minus.  Some of them in decorator colors look quite good.

One done well will probably be the last one you will ever need-- unless you get tired of it.  Then you may say, well, well, well-----guess I will hafta get rid of that roof or I will really be tired of it later.  :-/

Some of the old corrugated tin roofs must be near 100 years old around here and still going.

From the National Park Service preservation information:

Sheet iron was first known to have been manufactured here by the Revolutionary War financier, Robert Morris, who had a rolling mill near Trenton, New Jersey. At his mill Morris produced the roof of his own Philadelphia mansion, which he started in 1794. The architect Benjamin H. Latrobe used sheet iron to replace the roof on Princeton's "Nassau Hall," which had been gutted by fire in 1802.

The method for corrugating iron was originally patented in England in 1829. Corrugating stiffened the sheets, and allowed greater span over a lighter framework, as well as reduced installation time and labor. In 1834 the American architect William Strickland proposed corrugated iron to cover his design for the market place in Philadelphia.

Galvanizing with zinc to protect the base metal from rust was developed in France in 1837. By the 1850s the material was used on post offices and customhouses, as well as on train sheds and factories. In 1857 one of the first metal roofs in the South was installed on the U.S. Mint in New Orleans. The Mint was thereby " fireproofed" with a 20-gauge galvanized, corrugated iron roof on iron trusses.

http://www.cr.nps.gov/hps/tps/briefs/brief04.htm

[Amanda_931]

Metal roofing is better for rainwater harvesting.

Although it may be hard to find coatings that are potable water certified.

[Larry]

You may have already figured this out with your research, but there is a wide range of metal roofing material out there.  I found some significant differences in price, weight, coatings, etc.  I looked at both options and ended up going with traditional shingles, mainly because it was something I already knew how to do.  the cost seemed to be about a toss-up.  Several others around here have used metal and it looks good and they have been happy with it.

[tjm73]

You may have already figured this out with your research, but there is a wide range of metal roofing material out there.  I found some significant differences in price, weight, coatings, etc.  I looked at both options and ended up going with traditional shingles, mainly because it was something I already knew how to do.  the cost seemed to be about a toss-up.  Several others around here have used metal and it looks good and they have been happy with it.

You might think that, but I've had trouble even finding any comprehensive information.  All my searches seem to give two types or results.  I get either contractor stuff or worthless redirect search sites.

[Bouncer]

Like amanda said it is great for rainwater harvesting if your going that way.
It is considered a must for a lot of people in snow country. It lets the snow slide off the roof easier.(careful if you slam a door). Installation is a breeze. Just screw it down with sealing screws. You can get them in what ever length you want.(a least up to 20 feet long) And most companys have all the trim to go with it. You will need to check with your supplier to find out what brand they sell.
Goodluck
kevin

[tjm73]

I do live in a snowy climate.  I like the idea of the metal roof for the long term, last roof I'll probably ever buy aspect.  The load bearing capabilities and fact that snow slides off easy is also atttractive.  We often get heavy wet snow.  

Never thought about utilizing my roof to harvest rain water.  Is their a significant benefit to that?

[dorothyinak]

The benifit is not having to haul your drinking water, if you are in that situation.  Also if you get rain, but local wells are deep or low quality, it would be better than having your water delivered...

We planned on doing that for our cabin, but I had not thought about the coating on the roof coming offf into the water, like Amanda was talking about....

What sort of coating is OK, if you plan on using your roof to collect rainwater?

[John_M]

I know this should probably be in the referral section but it is a fairly good article that describes some basic information on metal roofing.  I found it helpful, especially since I too am looking into putting on a metal roof.

http://www.traditional-building.com/article/mroof.htm

[jraabe]

Thanks John, that is a good resource.

I'll add it to the referral section.

[ken hilfiker]

I used Perloins instead of decking on my 20x30 cabin.  Made installation easy.  Lift truss, tack to a couple of perloins, add remaining perlins at 18" spacing.  We then stood on cross member of truss and between perloins to screw sheeting down.  Only had to be on roof to do last row of sheeting and ridge cap.

[jimbob44]

If you already have a shingle roof, is there a coating that can be applied that will make it more suitable for rainwater harvesting?

[Amanda_931]

Another good reason to catch at least some rainwater is so you can spread the water out as irrigation instead of into storm drains--or just eroding your hillside.

I think I put a link to some high-tech coatings that are potable rain-water certified in the referral section--sure did--under not-metal roofing.

If you were not planning on drinking your water, almost any (Residential quality, not agricultural quality metal roof will do.  My guess is there is very little out-gassing or leaching from the baked-on coatings.   Especially after a couple of months.   Washing clothes, dishes, even showers are probably fine.

Somebody has or had a baked-on enamel that was drinking water safe.  I couldn't find it the other day, but that was what I had actually been looking for.

Dan Chiras, IIRC, in one of his books, said that the ag-quality roofs eventually leak.  Thus the specification up there.  

Don't think it would be reasonable to coat shingles.  But the next time you redid the roof you could use an EDPM coating or membrane over the sheathing.  There are a couple of suppliers there, the one in the referral section and the guys who advertise in Fine Homebuilding.  (I think they're different).

The Texas manual on rainwater harvesting is pretty standard.  There's a new edition this year.  They give, unless they're left out of the new edition, a wide range of approaches--from a couple of 55 gallon drums under the downspout to a buried 22,000 gallon cistern.  I have friends in the Western Pacific with the latter.  They love it.  Even when they have to go up on the roof during the first rainfalls of the wet season to clean out the gutters.

www.twdb.state.tx.us/publications/reports/RainHarv.pdf

[Okie_Bob]

I wanted a metal roof but, when I began construction, the cost was much higher than standard composition. By the time I was ready for the roof, lumber prices had gone up to the point that metal was the same as composition when you consider no plywood sheathing needed for metal.
I went with metal and then had the underside sprayed with Icynene and absolutly love it!
The Icynene supplier has convinced me that I made one mistake, I should have not used any ventilation in the roof! I already had installed a ridge vent and soffett venting material (Hardiboard). If I had to do it over, I would not vent the attic.
One other note, if you go with metal, you'll have to use a ridge vent. But, they sell a strip foam material that you can place between the ridge vent cap and the metal grooves. This keeps out insects and stops the flow of air. I also used it on the ends of the metal where it contacts the ledger board to completely seal the attic from insects.
In the south, you can buy from Metal Mart but, not sure they are nation wide yet. Many other places sell the material and most of the places have experts on staff that offer all the free advice you need to become an instant expert! It's a breeze to install and I highly recommend metal roofs!
Okie Bob

[John_M]

Very helpful information Okie_Bob!!  Thanks!

[rob]

I installed a metal roof on my cabin I am building and have yet to put on the ridge cap.  I put 1/2 inch r board under the metal and have debated on putting the foam under the ridge.  Some people I have talked to say it isn't advised because there needs to be air circulation between the r board and the metal.  Can you give me any insight into this.  I felt it would be good to put it but I am unsure of what to do.  Thanks in advance.

[glenn-k]

That seems like a bit of a hard one, Rob subject to various opinions.

I think the ventilation may be of more benefit than plugging the holes.  The main reason I can think of for plugging the holes would be to keep critters out, but I assume you have that taken care of with the r board so it seems ventilation to prevent condensation and heat build up would be of more benefit.

Maybe there are others with other opinions.  

[jraabe]

Here is a 44 page PDF report on both the history and present ideas about roof ventilation. This from Building Science Corp. (about as close as you can get to reliable research)

http://www.buildingscience.com/resources/presentations/Roof_and_Attic_Ventilation_Issues_in_Hot-Humid_Climates.pdf
(this will take awhile to load)

Here is a second article (from a foam insulation company - but the discussion is objective).
http://www.foam-tech.com/theory/roof_vents.htm.

I think the real question is can you insure that the attic or roof system will not be getting humid warm air from the interior into the roof structure. If you can then you don't need to vent the roof.

[rob]

I failed to mention that I am putting in a cathedral ceiling.  I will be putting in r-19 insulation in the ceiling.  I'm not sure if this changes the situation any.

[Okie_Bob]

Seems there are varied opinions on wheather to vent or not to vent and so far, I'm about as confused as I assume everyone else here is.
One thing I do know is that here in E Central Tx, if you use a ridge vent in a metal roof, you have to somehow close it up to prevent dirt, insects, dry leaves, etc from entering the attic. This means if you use soffet venting, as I did, you have to have a vent of some sort to exhaust the air. I installed an electric exhaust fan (thermostat controlled) in the gable end of the building. Suspose you could use one of the power vents that mount on the roof itself but, I prefer not to penetrate the metal roof unless absolutely necessary.
I installed my metal roof a year ago and did not install the foam blocking material in the ridge vent. I also did not have the Icynene sprayed in until this past spring. I would sweep the floor clean after a weekend of working on the rest of the building and return the next weekend to find a surprising amount of dirt and leaves had blown in thru the ridge vent, the entire lenght of the building. I also noticed a large number of wasps (mud daubbers) inside the building. The only way I could figure out to stop this was the foam material between the ridge cap and the metal roofing material. I easily installed it and stopped both the infiltration of insects and dirt and leaves. It was cold inside the building until this past spring when I had the insulation installed and what a difference it made!!
This will be my first winter with the attick completely finished so I can tell you more next spring when I have weathered at least one winter.
Not sure this helps. Just wanted to share my experiences in more detail after getting emails from a couple of posters.
Okie Bob

[ken hilfiker]

I used the ridge vent with the porous mesh material that keeps our leaves, wasps.  Used the blocking with vents cut in it per John's drawings between trusses.  Used spray cans of foam to fill the space between the perloins and the end trusses.  Works for insects and snow!