New roof on a cedar home... Some questions?

[gates]

Tom,
Darren is correct. I use standing seam panels with purlin spacings up to 6' o.c. . The gauge of the metal, the width of the panel, the height of the standing seam, the type of seam ie. snap lock or mechanical seam, and any perforations in the panel decide the spacing that the panel can span under the loading conditions that you want.
Rather than make your own built up roof use the SIPS. They can be made to order in any length, thickness, and material you want, either plywood or OSB. SIPS will also give you your substrate under the metal if that is what you want, once again not necessary. You can measure your roof and have the SIPS made top fit. This will be a huge time saver considering having the roof off of your house for any length of time opens the possibility of a rain and that would be a real problem.

Ron

 

[EddieWalker]

</font><font color="blue" class="small">( With regard to whether or not to use solid sheathing. Here is a clip from the Mueller web site on their standing seam product:

"Our Concealed Fastener (CF) Panel conceals the fasteners with our unique lock-joing system, with a minimum of penetrations in the exposed panel. This panel is for residential or commercial applications and should be installed over a solid substrate. It gives a smooth, clean look to any home or business. "

http://www.muellerinc.com/panels/cfpanel.php

Sounds like they prefer sheathing... /forums/images/graemlins/smirk.gif )</font>

Tom,

Soundsl like your doing your research on the material available. Like the others have said, you have allot of choices, and once you make the decision on what you're going to use, then you can decide on the method of supporting it.

A "CF" panel is different then the "R" panel I recomended. I'm also not sure wether a "solid substrate" is sheathing or perlins, but will accept sheathing for the sake of argument on that type of panel.

There's nothing wrong with useing sheathing. I think it's a level of overkill that you don't need. It's a ton of work, it will cost you thousands of dollars extra and there isn't any significant benifit on a metal roof.

Using a 26 guage material will be extremely strong and capable of holding your weight easily along with withstanding 100 mile per hour winds. I'm talking about using the good stuff here, not corrigated tin or anything you can buy at Home Depot or Lowes. There metal is fine for a shed, but not a home.

Eddie

 

[PILOON]

Just had to jump in!

I have re-roofed quite a few lindal homes as well as pan-abodes.
Both use same approach. Heavy beams covered with T&G 2 X6 stock, generally laid from top to bottom.

Now here we get down to -25deg so insulation is needed.

We have found that the most 'cost effective' approach that works is to lay 2" foam insulation over the whole roof 'deck' and then we use 2x3 or 2x4 purlins (laid on the flat) every 16" laid left to right.
This gives a good support for the tin roof and 1.5" is decent venting.
I use 5" 'box coated nails' to fasten the 2" (1.5") purlins to the T&G roof decking underneith.
The box nails are thinner and won't split the purlins but wont show inside.
We use the special rubber gasketed screws (matched color) on every second purlin on each tin 'ridge'.
Also add a screw on other purlins where the tin overlaps for a better seal.

Since the tin roofing will always 'sweat' air must circulate and we then use strip vents all along the ends of the purlins. This will allow a fair 'cross venting', enough to dry out the condensation.

The foam boards we use give about R-15to20 and I opt for those that have notch for good seal. (The red tape could also be added).
These foams are actually closed cell so they will not absorb water.

Tin roofing when placed directly on sheething will always rust from the backside dur to the condensation, so don't even consider that.

Someone mentioned 'galvanume'-yes, that's the way to go.(without it rust could show as soon as 8-10 yrs)

As far as buckling of the tin goes, the instructions are quite simple. ONLY WALK ON SCREW HEADS! A- no slipping, B- you know that there is a purlin under them!

Now this approach can carry the 4 ft snow accumulations that we have every winter up here.

Another point not mentioned:
If your 'pitch' is less than 4/12 you are asking for trouble with tin roofs. Especially if you have dormers or inside merging roofs. While the fabricators have special flashings for converging roofs, I have found that the water that rushes down one roof still wants to splash under the other roof.
Lots of caulking while installing is about the only answer.

For me tin is great for a 2 faced plain roofs and deffinately not less than 3/12 pitch for sure. (on a house)

Now in reality R40 is needed up our way and what I described is a 'balanced comprimise' that works. Generally it is when the owner absolutely wishes to keep the inner 'look' and while improving accepts the higher heating costs vs the cost of adding a whole foot or of structure to attain that R40.
Essentially we are converting a summer chalet into a 3 season home.
I have also added sissor trusses atop of existing 2x6 T&G to create a 'real' year round home from a 50's cedar chalet.

Oh yes, for cutting use a 'friction blade' on your skill saw.(not abrasive blades).

For nice screw patterns, I stack 6 sheets at a time and 'gang drill' pilot holes at the correct spacings and always keep one sheet to use as a pattern. Works great!.

Good luck, you must be slightly confused by now! LOL