Thicknesses range from 5 16 to 3 4 inch and the proper one to use.
Osb over existing sheet metal roof.
Use 1 1 4 inch nails to cover the outline of the roof with strips of metal eave flashing also called edging.
Oriented strand board commonly referred to as osb is a type of engineered lumber similar to particle board formed by adding adhesives and then compressing layers of wood strands.
Stagger the panels over the roof with 2 supports between panel ends.
A homeowner recently wrote and asked me the following regarding osb roof decking.
3 install 1 4 purlins down over the shingles before installing the metal roof the third way to install a metal roof over shingles is by applying 1 4 purlins over the shingle roof.
Table 2304 7 3 gives the 7 16 osb the ability to carry a roof live load of 40 psf pounds per square foot when spanning the same 24 inches.
Roof trusses must be dry when sheathing a roof with osb to prevent mold growth in the roof and coverage gaps as the trusses dry and shrink.
Avoid butting osb panels tightly leave a 3 mm 1 8 inch gap between the osb panels to allow for expansion.
Today a shiplap roof is usually 60 years old.
This is by far the most common way to install a metal roof.
If there are gutters installed on the eaves the eave flashing should be installed to overhang the lip of the gutter by about 1 2 inch.
Osb comes in 4 by 8 foot sheets as does plywood but the manufacturing process allows the production of longer and wider ones.
Open spaces form between the once tightly fitted.
In the case above the shear forces in the last 12 foot bay at each end of the roof have had osb placed between the roof purlins and the steel roofing.
After the 1960s the predominant residential roofing substrate became 1 2 cdx plywood.
When the steel roofing can t carry the load other shear carrying materials such as 7 16 osb may be added to the assembly.
Osb is widely used as roof decking material.
Why re sheet over shiplap.
Over time shiplap fir wood resin dissipates causing the boards to shrink crack form knot holes and become extremely brittle.