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Open valley    Method of valley construction in which shingles on both sides of the valley are trimmed along a chalk line snapped on each side of the valley. Shingles do not extend across the valley. Valley flashing is exposed.  

 

Organic felt    An asphalt roofing base material manufactured from cellulose fibers.  

 

Oriel    A bay window supported by brackets 

 

Oriented Strand Board or OSB or Chip Board or Wafer Board     A manufactured wood panel made out of 1"- 2" wood chips and glue. Often used as a substitute for plywood in the exterior wall and roof sheathing.  

 

Out building    Any small building(s) located on the same property as, but clearly subordinate 

 

Overhang    The portion of the roof structure that extends beyond the exterior walls of a building offering it protection from the elements.