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to a letter:
O
O-Ring:
Round rubber washer or gasket that is compressed to create
a watertight seal, typically in a compression fitting.
O. G. (or
Ogee): A molding with a profile in the form of
a letter S; having the outline of a reversed curve.
Oakum:
Loose hemp or jute fiber that is impregnated with
tar or pitch and used to caulk large seams or for packing
plumbing
pipe joints.
OD (Outside
Diameter): A measurement of the diameter of a
pipe as taken from the outside edge. A common method for
sizing
pipe.
Offset:
A tubular component which permits the offsetting
of a drainage run in the same basic direction.
Ohm's Law:
States that, in a given electrical circuit, the
amount at current in amps is equal to the pressure in volts
divided by the
resistance in ohms.
The formula is: I (Current) = V voltage or V = I x R R resistance
or R = V/I.
Ohmmeter:
In electrical contracting, a device to measure
the resistance across a load. They are never used on a live
circuit. Used
to track down broken
wires.
Oil-Canning:
The term describing distortion of thin-gauge metal
panels which are fastened in a manner restricting normal
thermal
movement.
On Center
(O.C.): A measurement term meaning a certain distance
between like materials. Studs rafters, joists, and the like
in a
building placed
at 16 inches O.C. will be laid out so that there is 16 inches
from the center of one stud to the center of the next.
Open Hole
Inspection: When an engineer (or municipal inspector)
inspects the open excavation and examines the earth to
determine the type
of foundation (caisson, footer, wall on ground, etc.) that
should be installed in the hole.
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:
A term designating any chemical compound which
contains carbon and hydrogen.
Organic
Felt: An asphalt roofing base material manufactured
from cellulose fibers.
Oriented
Strand Board (OSB, Chip Board, 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.
Outrigger:
An extension of a rafter beyond the wall line.
Usually a smaller member nailed to a larger rafter to form
a cornice or roof
overhang.
Overhang:
That part of the roof structure which extends
horizontally beyond the vertical plane of the exterior walls
of a building.
Oxidize:
To combine with oxygen in the air.
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