I have 7/16 OSB, not plywood. Also, in my opinion, there are an excessive amount of nails showing in the attic now. The sheathing looks like a pin cushion. My son said that the insulation seems damp up there too. Could the excessive amount of nails be causing moisture problems now or later on?
7/16" OSB isn’t thick enough for 24" spans, you need new decking.
I did one like this once, the guy built it himself.
The decking was sagging between the trusses everywhere and it was spongy, 7/16" just isn’t thick enough.
I would go to 5/8" OSB or Plywood.
So how much does decking cost on a 37.55 sq roof? Is that what is causing the telegraphing of the rafters through the shingles?
Most areas code is for nails to penetrate 1/4" through the underside of the decking. No, nails are not causing excess moisture in your attic.
I don’t like 7/16 osb on 2’ centers either but it does meet code in my area. I can’t remember the last time I roof a new construction house that had anything but.
For 24" oc we will use 5/8" plywood minimum, personally would not recommend 5/8 osb. If the 7/16 osb is sagging it has to come off, new plywood will not sit correctly on top no matter how many screws somebody claims they will use.
Believe it or not…Shingle manufacturers only require 3/8" decking. N.C. requires 5/8". CDX plywood 5/8" will avg about 1200$ Fiona…5/8 OSB will avg about 700$ That’s just the plywood. Every “Contractor” has their own opinion…engineers say OSB is stronger and more consistent. OSB will only be a draw back if wet and even then it depends on how long its left to be damaged. CDX plywood is known to be prone to delamination without moisture and doesn’t actually hold up much better in the event of a leak. You can get as many opinions as people you ask…I trust the designers and manufacturer’s…that way its their problem if “I’m” wrong…lol
Keep in mind the decking in question is a reroof and 20+ yrs old.
This house is around 15 years old. Are the prices $1200 for 5/8 plywood and $700 for osb include materials and labor? Will this help eliminate the rafters showing through the shingles or is this caused by something else?
That is material. I can’t quote labor in your area. Yes…it should eliminate your issues assuming they only install shingles over “flat” underlayment😀
Apoligies@Fiona…5/8 OSB cost avg 2100$…5/8 CDX plywood 3700$. I forgot to add formula per square.
So I am wondering if my insurance should have brought me up to 5/8 from the 7/16 or this is not code where I live and I would be responsible to pay for the upgrade?
Usually insurance is ACV…actual cash value. If you want better than what you had…you will have to pay difference. Not sure how that works when requirements change. Depends on policy and company I’m sure.
Really depends on what the code is where you live. 3/8 on 24" centres is the norm here. An hour away they require 1/2" on 24" centres. Codes are different everywhere
Thanks for all the replies. I am learning so much about roofing. So back to temperature. Can the existing shingles be inspected for overdriven and high nails in cold weather? Weather between 65-40 degrees?
Should be no problem. Do it in the warmer part of the day and before the activator begins to seal.
Is it possible that the roofers could have damaged the 7/16 sheeting by stepping on it with heavy weight from carrying shingle bundles or a bunch of the tear-off shingles across the roof? I have a picture of one worker carrying a big stack of tear-off shingles. Also the sheathing looks sunk in around the area where they had a ladder. Just a thought.
No that isn’t an issue.
It should never had been built with that thin of sheeting to begin with, putting heavyweight shingles on it will just make it worse.
I live in Michigan where we get a decent amount of snow so thin sheeting like 7/16" over 24" spans just doesn’t work here.
Even when new the deck will deflect when stepped on, the plywood clips sometimes flip over also.
Going into the attic and adding perlins is really the only cure for that. If its accessible. To clarify: perlins= 2x4s cut to length and affixed between the rafters to help support the decking between the 24" span. Also would be more effective if done before new shingle installation and decking is attached to perlins.
Adding perlins or blocking at this much would be pretty much impossible at this point, and after any labor intensive. The nails from the shingles penetrate the osb, so in order to get the 2x4 tight to the decking To actually support it you would need to drive the nails back up into the shingles.
Unfortunately the only real way to fix the appearance of the roof is remove the shingles and decking and reinstall.
Our company policy for the past 20+ years, no matter if it is 16" or 24" rafters is to install 5/8 cdx. If you are paying for the labor to remove and reinstall the decking there is no point to use anything thinner to save a couple bucks.