 |  |
| Off-Ratio Foam | SPF where the 1 to 1 ratio of the A and B components has been compromised and which results in a lower quality material. |
| Open Time | The time after an adhesive has been applied and permitted to cure when the two surfaces can be bonded. |
| Open Valley | A valley where both sides of the roof are trimmed back from the centerline to expose the valley flashing material beneath. |
| Orange Peel Surface Texture | A surface with a texture comparable to the skin of an orange upon which a protective coating may be applied. |
| Organic | Formed from hydrocarbons. |
| Organic Felt | An asphalt roofing base material manufactured from cellulose fibers. |
| Organic Shingle | An asphalt shingle reinforced with organic material manufactured from cellulose fibers. |
| ORNL | Oak Ridge National Laboratory |
| OSB | Oriented Strand Board - Often used as roof sheathing in place of plywood. |
| Overlay | See Re-Cover. |
| Overspray | The loss of spray particles (from coatings, SPF, etc.) in the air. |