Decks/T&G roof deck


QUESTION: While replacing the roof covering on my flat roof I discovered that the 2 x 6 T&G roof deck (Western Red Cedar) was deteriorating in a large area on the 18 x 33 roof deck surface.  I plan on replacing the majority of T&G Cedar.  I have an open beam ceiling and, after checking the grain pattern, found the majority of T&G roof deck boards only span 120 the boards are staggered.  Will changing board lengths to span 180 make a difference to the integrity of the roof deck structure?  And, should I use wood screws when installing the boards to the seven 4 x 10 x 18 rafters spaced 60 OC?

ANSWER: Ok, so let me see if I'm understanding your situation correctly... In order to do that, I need to ask a few questions...

You have 2x6 tongue and groove decking over an interior living space? I'm guessing that the cedar boards are seen from the ceiling below, but not from above, and that there is roll roofing, or some other type above it...?
So, if you're saying that the total length is about 33', and the cedar board run that length, they used about three 10' lengths per row. Where the "butt seams" fall should not matter much, as long as the beams under them are of equal and adequate support strength. Definitely stagger your end (butt) seams as much as reasonably possibly for the most strength.
As far as screws, I would try to use an adequately sized stainless steel screw (or at the least, an exterior type coated screw) galvanized can react with the natural chemicals in the cedar.

Well, I hope this answered your questions, but if not, don't hesitate to ask more.
Best of luck with the project! :)

---------- FOLLOW-UP ----------

QUESTION: Thanks for your response.

Your paragraph 1 is exactly correct.  The support beams are 60" OC.  The extra 3' is for the eaves.  Will the only benefit from using longer boards be less labor hauling material to the roof?  I was thinking longer boards would add additional strength.  I'll probably use Deck Mate brand screws, they have held up well on other projects.  Do building codes usually specify a preference - nails or wood screws?  Or, are wood screws better than nails but not practical for residential construction?

Well, since your beams are spaced 5', 10 footers make the most sense. Not much strength would be gained with longer. If you really wanted to though, you could buy 16 footers and waste 1 foot per board. Deckmates should be fine, for code AND for strength. Screws vs nails is personal preference here. Screws generally have more holding power but less shear strength. I'd go screws with this so there is less worry about pop ups later through your roofing material.  


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Michael Romano


I can answer any questions relating to decks, porches, exterior stairs & railings, walkways, access ramps, pergolas, deck roofs, screen rooms, etc... These may include design ideas, footing to framing design & construction methods, various species of woods vs. composites & pvc/vinyl materials for decking, skirting, or railing applications. I also have expertise in various rain-free systems for under-deck storage & living spaces.


I have designed and built decks and many other types of outdoor structures for over 25 years for my own home improvement company. We also perform many other types of home improvements, including window & door installation, molding & trimwork, siding, basement finishing, siding, etc. Our main love however, is decks!

NADRA - The North American Deck and Railing Association. Several Small Business & Home Improvement Contractor Alliances & Associations.

I have written several articles over the years for,, and many other deck & construction related websites.

High School graduate. 2 years of Mechanical Drawing & Architecture classes. Vocational School graduate. 2 years of Construction Technology & Carpentry classes. Many years of reading, researching, and application in the real world.

Awards and Honors
I am certified by several decking manufacturers for expert application & installation of their products.

Past/Present Clients
Mainly local residential clients, and occasional commercial clients, including restaurants, nightclubs, office buildings, etc.

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