Attic soffit ventilation / underlayment / plywood decking


#1

I had some general questions about roofing. Thanks in advance.

  1. Is 4 ply plywood necessary for roof decking or is 3 ply sufficient?
  2. Can ½â€Â

#2

here we go !!!
1)
2) If plywood is now 3/8, I would recomend that it be replaced w/ minimum 7/16 O.S.B. ,and if rafters are @ 24" o.c. you must use plywood clips.
If you prefer to use plywood I would recomend that it be 4 ply min. and if you choose not to re-sheet entire roof deck, you should not mix 3/8 and 1/2 …you replace w/same as existing…Also pull all loose sheathing nails and re-nail entire deck w/ 2-3/8" nails…(if you pound in loose nails, they will come right back up through your Beautiful new shingles!)
3) If you take up the bottom row of plywood (use caution for the BEES!)it is possible to cut vents in soffit between rafters from above to add intake vent…IF YOU ARE PRO ! (keep in mind when that if you had lack of vent…you should seriously consider new decking.)
4) The GAF/ELK shingles can be installed w/ 4 nails if it is less than 12/12 pitch…(I nail 4-6 on any low sloped )also shingles must be nailed on the nailing line, or you can forget about any warranty!
5) I use what is called the smart choice system GAF/ELK w/ Timberline Prestique high def. shingles.,Shinglemate paper( is breathable felt) and less cost than Deck armor(unless the roof deck will be exposed for a long period of time) Deck armor is designed to last for months exposed… otherwise Shinglemate is a fine choice…( after using Shingle mate paper I would never use regular felt again…)
Gaf/ weatherwatch I&W shield(2 rows at bottom edge and be very carefull as this product is very slippery to walk on in the sun!) and Cobra rolled vent( with a minimum ply wood cut at ridge of 1-1/2"from each side of ridge board! )
and to cap it off use Seal a ridge or Timbertex caps.This system gives you a fully intigrated roof system , that if ( installed properly!!! ) should provide you w/ many years of performance and beauty…
I wish you good luck in your roofing project… If you need a professsional installation I am in N.E. P.A. and Will travel…also I am not cheap!!!


#3

1) Is 4 ply plywood necessary for roof decking or is 3 ply sufficient?

Don’t know…we use CDX… /shrug

2) Can ½â€Â


#4

Thanks for the replies. Just to clarify question 2), I would like to replace the rotted 3/8"plywood and didn’t know if it was OK to replace them with 1/2" which would leave my rood with some 3/8" sheets and some 1/2". The Consensus is to use all the same thickness but one roofer said it was OK to mix thicknesses on the same roof.

For question 3, I have not intake into the attic. I wanted to find a way to get intake into the attic since this is probably how my plywood got saggy an ruined. I assume intakes can be added to an old construction house. Then I could go with a ridge vent.


#5

Just to clarify question 2), I would like to replace the rotted 3/8"plywood and didn’t know if it was OK to replace them with 1/2" which would leave my rood with some 3/8" sheets and some 1/2". The Consensus is to use all the same thickness but one roofer said it was OK to mix thicknesses on the same roof.

No, don’t mix sizes.

For question 3, I have not intake into the attic. I wanted to find a way to get intake into the attic since this is probably how my plywood got saggy an ruined. I assume intakes can be added to an old construction house. Then I could go with a ridge vent.

everflovent.com/pro_inhaler.html

gaf.com/Content/GAF/RES1/ROO … oster.html

2 options for intake venting.


#6

It is my understanding that you have vented vinyl soffit existing wood soffit,you can vent this by cutting the wood soffit from above after sheets are removed.


#7

Sounds risky to me. I’m sure some people are confortable doing it, but I would cut it from the soffit.


#8

good stuff guys.
hell i appreciate it.

gweedo