So I replaced 2 shooting roofs this year. Both took 2 sheets of 4x8 particle board. I just replaced old with new. Sealed seams where they met and even put another strip of OSB over the seam. Still had water seeping into house soaking the chairs and floors so I’m going to put metal roofs on them now. My question is should I just pull off the OSB and replace it or can I just put new metal on top of OSB. I’m worried that water will get under the metal and soak the OSB and I’ll have an issue there. All opinions welcome.

just strip with 1x4 over the existing osb and make sure you have good overhang with the metal and you should not have an issue.

Why would you use particle board?

It was cheaper than plywood…by a lot. Got what I paid for I guess.

Put the metal over the OSB with plenty of overhang as JKlep said . Lathing strips are optional IMO on the OSB for a shooting house application.

Wait, is it OSB or particle board , there's a difference . Particle board and water don't mix , it should never be used for subflooring , storm sheeting or roof decking. OSB is what's used most nowdays.

Particle board. I was thinking they were same thing. Not the case.

you can try this on the joints - I've used something similar on a 5th-wheel roof (rubber membrane was leaking). It will seal the joint - maybe use a couple of staples in areas that you think might curl.

https://www.amazon.com/Typar-Self-A...71J3/ref=cm_cr_arp_d_product_top?ie=UTF8

I would use the metal roof seam tape if you are using more than one sheet width of metal roofing panels. I am guessing the roof is not flat but if flat I would create a slope for the metal.

Great minds.....

Particle board acts like a sponge!

I'd take it off and lathe it with 1x4 or 2x4 and not even deck it , unless you want to seal it, then use OSB or exterior plywood. 1/2" 3 ply would work for plywood.

Just high humidity will cause particle board to swell and come apart. It needs to "breath" but be in a dry location. It's rarely used in residential construction now. Used to be installed between carpet and subflooring.

Screw the metal roof on the particle board. You will be fine.

After the April showers , the particle board will swell, deteriorate rapidly and the screws won't hold. He'll have to completely re-do it in a year or two .

Can you paint it with a good elastomeric roof coating paint?

Yeah Particle board doesn’t like moisture at all. I’d strip all of that stuff off

bamaeyedoc - are you talking particle board or OSB?

I put osb under my metal for the noise dampening when raining, acorns falling, etc

Problem solved.

Remove particle board and replace. Then use metal with good overhang as roof you can replace particle board with osb or plywood if you want

I have some roofing tarpaper you can have if it would help.