Because osb holds water prolonged exposure to roof leaks or excessive humidity and condensation in unvented attics can cause osb roof panels to degrade faster than plywood panels.
Rot resistant roofing osb.
With a weather resistant barrier like tyvek over the osb and then cover that with siding of some sort.
Solid wood rafter tails on the exposed underside of roof eaves having a minimum 2 nominal dimension may be unprotected.
Even rot resistant woods can become vulnerable over time or with extreme conditions.
Since osb holds water prolonged exposure to roof leaks or excessive humidity and condensation in unvented attics can cause osb roof panels to degrade faster than plywood panels.
There s no such thing.
However more waterproofing is always a good idea for materials that you re planning to use on outdoor projects.
The zipsystem is a great all in one osb sheathing panel that has the building wrap already attached to it so all you have to do it tape the seams.
Roofing underlayment is what lies between the shingles and the roof sheathing or roof deck which is typically either plywood or osb.
These have the highest resistance to rot over time.
Cbc 706a crc r337 6.
Osb is great for walls and roofs and for subfloors i m particularly fond of an engineered wood panel similar to osb called advantech.
Compounding this weakness is the fact that osb is often made from aspen and poplar which are not rot resistant woods.
Osb will swell warp and degrade unless it s kept safe from sunlight and perfectly dry.
When a wood is in direct contact with the ground it opens the wood to mold and fungus because it allows moisture to penetrate the wood.
So how do you stop wood rot in those cases.
Osb is said to be more water resistant than plywood by some and not so by others.
It s installed directly on the roof deck and provides a secondary layer of protection from the elements including rain snow and wind.
If you want to use osb to sheathe the walls of your shed you need to build those walls like the walls of a house.
Compounding this weakness is the fact that osb is often made from aspen and poplar neither of which are rot resistant woods.
The exposed roof deck under unenclosed eaves and underside of porch ceilings shall be noncombustible listed ignition resistant materials or 5 8 type x gypsum sheathing behind exterior covering.
How to stop or prevent rot.
If you re using a wood outside starting with a rot resistant wood is the most important step.
After following these steps you will never risk moisture ruining your work down the road.
The resistance of osb to rot depends on the material from which it is made.