Hello,
I am building an addition on my home that includes a new roof over the whole structure. The new roof is a typical gable end roof with a 9/12 pitch. I have 1/2″ plywood installed over rafters with full blocking. I have spoken to a few people about the best way to install the metal roof. Some say directly over the 30lb paper screwed into the plywood and others recommend purlins spaced 16″ on center. One guy suggested a foam type insulation in between the purlins. Any suggestions or opinions would be very much appreciated.
Thanks,
Bob
Replies
Some have also said to use Titanium "paper" so it doesn't react with the chemicals in the felt paper.
I'm getting ready to do our roof in 5v as well. We're in Tampa also. You'll find alot of answers on this forum if you do a search.
There are threads on what screw is "best" to use
Who are you going to use for your supplier?
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I am getting my roofing from Marlyn Steel, If your interested let me know and I can give you my number and will let you know what research I have done locally.
Bob
What does the manufacturer recommend? Many will not honor a warranty if it's placed directly on felt paper. Titanium is hands-down better than felt most roofing applications, so I would use the regardless - it's not much more expensive.
Is your roof perfectly flat? If not, it will telegraph though the metal. In this case, purlins would definitely be better.
Where are you located? Do you have wind codes to worry about?
Don't use purlins. After hurricane Charlie the only metal decks that I saw blow off were the ones attached to purlins. My roofer confirmed my observation and commented that the only ones he had ever seen blow off were screwed to purlins. I've never seen a south Florida roofer use purlins.
The manufacturer recommends either installing it right over the 30 felt or with purlins. Their only requirement is no PT lumber under the metal roof and no metal washers securing the felt. Since the hurricanes there are new codes as to the nailling schedule for purlins. I have talked with them about what their roofers are doing and from what they tell me both are fine as long as the purlins are secured per code. After this past years storms I worked in Stuart, Fl where 2 of them hit and found that the metal roofs with the gable flashing that secures directly over the gable end of the metal roof section and to the facia faired the best.
Bob
I live just north of Stuart in Melbourne, where we faired better from Francis and Jeanne. The damage to metal roofs in my area generally came from weak and/or inadequate fastening at the edges. Once the wind got under the lip and started to peel a section back, a lot of the roof went with it. I'd say about 1/2 of the reroofs in this area are using purlins.
If you're not already, I'd recommend using the heaviest guage you can - probably 24, rather than the thinner 26 or 28 guage.
Good luck!
Definetly go with the heavier gauge particuliarly if u ever plan to walk on it.The 29g. is like a flattened beer can and hail will give a nice pebbled finish.Being in Fla, u probably dont have to worry about big temp diffrences on either side of the tin but after years of using purloins/nailers i swear I ll never do it again after seeing the condensate form in the attic on the bottom side of icey tin.One house where i was doing trim work we saw water drip out of the recessed cans where the warm air leakage around the can thawed the frost on bottom side of the frozen roof above.Now its ply and felt plus u can stack sveral sheets and predrill all ur screw holes and not worry about missing a nailer.
Kind of depends where you are I guess. The strapping/purlins is a way to create a cold roof and reduce ice daming in the north. I can see the potential for greater wind damage in Florida's hirricanes, but all that would also depend on the entire fastening schedule.
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