OSB over OSB

I am looking to replace my own roof in April due to sagging roof and putting on better Arch. Shingles…Anyway on one side of my roof the sheathing is sagging It looks like they put them on wrong going up instead of across the rafters and they are sagging, can I put OSB sheathing on top of the existing deck…I have a tri-level house and only looks like I need to do this on my top floor roof… Thank you in advance…Steve

Yes you can.

I’ve done it numerous time. I would recommend installing the H clips still.

putting on added sheathing will not pull up or level out ant present sagging however if you think it is neccessary then go ahead it won’t hurt…

you may need to provide support to jack-up your existing rafters inorder to remedy curb side appeal

I am guessing that he has 3/8" 3 ply plywood on his roof.
That crap always sags and delaminates. :frowning:

Yes. The roof weight heavy and the nails must longer .

why not just use plywood ? OSB is garbage.

I am curious, why is that?

ever reroofed a house that had OSB ? you would know why.

osb , plywood , doesnt matter.
ive seen em both last 20 +.
what does matter is that you take off one peace,
put one back, get them all on, running the proper way.
if its not code do not use plywood clips
(im tired of seein em back up thru roof and
cause leaks).

when done you will probably, be happy.
if you have a low rafter or 2, you can fix

im not a fan of deckin over deckin.

damn plywood clips neither.


I do it all the time, that is why I am asking for your opinion.
I see more plywood delaminating than bad OSB.

I have seen a lot of bad OSB around here. It delaminates,sags and just turns to crap in general. we end up pulling it up and using CDX plywood.

I do agree that quality plywood is better than OSB.
Quality being the key word here.
OSB is far more consistent, quality wise.

I’ve never experienced any issues with OSB provided it’s out of moisture (i.e. roofed fairly soon after laying it down).

As for H Clips, Gweedo… well, I don’t know what to say.

Skipping a few here 'n there isn’t so bad if it’s a repair situation is OK but for a total redeck I’d use 'em every time.

OSB has a wax impregnated coating, IMO it stands up to weather exposure better than Plywood.
I am not sure but I think that exposure to the elements is part of the reason for plywood delamination.

i dont know ranch,
we got along just fine for a hundred years
without clips.
reroofed alot of old plywood houses without clips.
doesnt seem to make a difference.
i can take em or leave em.
but would rather leave em.



How many centuries did we “manage” to go on without advancements like written alphabets, the printing press, telegraph, telephones, fax machines & computers?

Same goes for living in caves or under fallen trees, mud huts, thatching (still in use) & fiberglass shingles?

Techological improvements march on, even in spite of curmudgeons.

ok ranch,
we can use plywood clips,
if it makes ya happy.

i still dont like them.


gweedo, be sure to take & post photos of a redeck you’re doing that has H clips on it.

'Cause I said to use 'em. Right?