- OC
- On center, the measurement between rafters or studs from the center of one to the center of the next.
- Open Ground
- If found on three prong electrical outlets, it means that the outlet does not have a working ground wire (the round hole), or it has a bad connection or disconnected ground wire. Dangerous condition, needs repair.
- Open Junction Box
- Electrical junction box without a cover, all junction boxes must have a cover.
- Open Valley
- Method of valley construction in which shingles on both sides of the valley are trained along a chalk line snapped on each side of the valley. Shingles do not extend across the valley. Valley flashing is exposed.
- OSB
- Oriented Strand Board, a compressed wood fiberboard. Used for decking, sheathing, and sub flooring. Comes in 4′ x 8′ sheets. Does not warp like plywood.
- Outrigger
- The extension of a rafter passed the wall line, commonly a smaller size piece of wood nailed to the larger rafter to form a cornice or roof overhang.
- Over Fused Circuit
- A circuit for the fuse or breaker where the amperage is too high for the wiring. Dangerous!
- Parapet Wall
- A party or firewall extending above the roofline. Any wall around a balcony.
- Parging
- A coat of plaster or cement applied to masonry or concrete walls.
- Partition Wall
- Dividing wall that has no load bearing function. Could be removed without affecting the structural integrity of the building.
- Performing Intended Function
- It works!
- Pier
- A column used to support other structural members.
- Pitch
- The slope of the roof or the degree of roof inclined expressed as the ratio of the rise, in feet, to the span, in feet.
- Pitched Roof
- The roof that has one or more sloping surfaces.
- Plumb
- Perpendicular, been perfectly vertical.
- Plywood
- A wood made of three or more layers glued together to make one board.
- PPM
- Parts per million
- Primer
- A basecoat or first coat of paint.
- Putty
- Typically refers to the glazing compound used on windows to hold the glass in the frame.