Glossary, 46 terms
Home inspection terms: O
Each definition is the Key Term from the lesson named under it. Where two lessons define a term for different uses, both are here.
- O'Hagin cover
- A flat or rounded roof ventilation cover.
Lesson 16C, Attic Ventilation and Closed Attics - Oakum
- Tar-soaked hemp, packed into cast iron hub joints and older clay pipe joints.
Lesson 37A, DWV Rules and Pipe Materials - Occurrence policy
- An E&O policy covering claims that occurred during the policy term, whenever filed.
Lesson 21B, Contracts and Insurance - Offer
- A promise, under stated conditions, to do something later or to hold back from doing it.
Lesson 21B, Contracts and Insurance - Official score sheet
- The score document a candidate receives when the examination ends, carrying a digital photo and a unique identification number.
Lesson 43, Scheduling, Taking and Passing the NHIE - Offset
- A section where a chimney leaves vertical.
Lesson 39B, Combustion Air, Masonry Chimney Construction, Liners, Flue Area and Defects - Offset (chimney)
- A bend that takes a chimney or flue away from vertical.
Lesson 39A, Fireplace Types and Terms, Firebox, Hearth and Clearances - Oil fill pipe
- The pipe through which an oil tank is filled; it should have a tight metal cover.
Lesson 38I, Oil Supply, Valves, Filters and Tanks - Oil filter
- A filter in oil supply piping that traps debris; recommended, not required.
Lesson 38I, Oil Supply, Valves, Filters and Tanks - Oil level gauge
- A gauge on an oil tank; indoor tanks and outdoor above ground tanks should each have one.
Lesson 38I, Oil Supply, Valves, Filters and Tanks - Oil line safety valve
- A fire safety device on the oil supply tubing that stops oil flow in a fire.
Lesson 32C, Oil Burners - Oil vent pipe
- The vent piping of an oil tank, ending near the fill pipe.
Lesson 38I, Oil Supply, Valves, Filters and Tanks - Oil-canning
- Excessive ripples in metal panels.
Lesson 8B, Steep Slope Roofing: Fiber Cement and Metal - One pipe counterflow system
- The oldest and simplest steam distribution type, in which steam enters and water leaves each device through one pipe at its bottom.
Lesson 33C, Steam Heating Systems and Distribution Piping - One pipe parallel flow system
- A one pipe steam distribution type in which the water returns to the boiler apart from the steam after the last device.
Lesson 33C, Steam Heating Systems and Distribution Piping - One pipe system
- 1. A layout that connects the input and output sides of each device to one pipe through monoflow tees.
Lesson 33B, Hot Water Heating Systems - 2. An oil supply arrangement with one line from the tank to the burner.
Lesson 38I, Oil Supply, Valves, Filters and Tanks - One-eighth bend
- A bend that turns the flow 45 degrees.
Lesson 37B, DWV Fittings, Cleanouts and Defects - Open cell foam
- 1/2 pound spray foam that passes liquid water and is not a vapor retarder.
Lesson 14C, Insulation Materials - Open eaves
- Eaves with the rafters exposed.
Lesson 4C, Exterior Trim, Flashing and Sealants, Eaves and Cornice - Open riser
- A stair riser with an open space between treads.
Lesson 6B, Deck Materials, Flashing, Ledger Attachment and Deck Stairs - Open system (gravity system)
- An old hot water system with piping open to the atmosphere and no circulation pump.
Lesson 33B, Hot Water Heating Systems - Open valley
- 1. A valley in which the metal valley flashing is left exposed.
Lesson 8A, Steep Slope Roofing: Asphalt Shingles and Tile - 2. A valley in which the metal flashing is left exposed.
Lesson 8B, Steep Slope Roofing: Fiber Cement and Metal - 3. A valley that leaves its metal flashing exposed.
Lesson 8C, Steep Slope Roofing: Slate, Polymer, Wood and Ice Dams - Open-loop
- A water-source configuration that takes water from an aquifer or lake and returns it to the source.
Lesson 28A, Cooling Systems: Understanding the System - Operable window
- A window with at least one sash that moves to admit outside air.
Lesson 5B, Windows, Window Flashing, Glazing, Window Wells, Escape Openings and Fall Protection - Orangeburg pipe (fiber sewer pipe)
- Building sewer pipe of wood fibers bonded by a waterproof adhesive and impregnated with coal tar.
Lesson 37A, DWV Rules and Pipe Materials - Ordinary negligence
- Also called simple negligence; falling short of the standard of care of a reasonably prudent home inspector in a similar situation.
Lesson 21A, Business Law, Claims and Liability - Organic shingle
- An asphalt shingle with a base of felt impregnated with asphalt.
Lesson 8A, Steep Slope Roofing: Asphalt Shingles and Tile - Oriented strand lumber (OSL)
- Structural composite lumber made of wood strands, usually looking more like OSB.
Lesson 12B, I-Joists, SCL, Glulam and Floor Trusses - Orifice (unregulated)
- An older, inefficient metering device that passes a fixed amount of refrigerant whatever the evaporator coil pressure.
Lesson 28A, Cooling Systems: Understanding the System - OSB
- A layered sheathing panel bonded with heat, pressure, and water-resistive adhesive; it swells and deteriorates when wet over the long term.
Lesson 12A, Floor Framing, Spans, Bearing, Notching and Boring - Out-of-scope component
- A component a home inspection does not cover, such as a fence, a spa, or an accessory building.
Lesson 19E, Inspection Limitation Statements and Other Report Contents - Outlet
- 1. Any point where current is drawn for use, such as a receptacle or a light fixture.
Lesson 23A, Electrical Terms and Basic Electricity - 2. The opening where water leaves a trap.
Lesson 38A, Traps and Fixture Drains - Outside air duct
- A duct to the HVAC return through which return suction draws outside air while the system runs.
Lesson 16A, Mechanical Ventilation, HRV and ERV, Whole-House Fans - Oven
- An enclosed cooking appliance for baking and broiling food.
Lesson 41A, Appliance Scope and Terms, Cooktops, Ranges, Ovens and Dishwashers - Over-the-range microwave
- The most common built-in microwave style, hung above a range and usually about 30 inches wide.
Lesson 41B, Microwave Ovens, Exhaust Hoods, Disposers, Trash Compactors, Refrigerators and Freezers - Overcurrent
- Current in excess of what a circuit is designed to carry.
Lesson 24B, Overcurrent Protection, GFCI and AFCI - Overcurrent protection device (OPD)
- 1. A circuit breaker or fuse that interrupts current on an overload or a short circuit.
Lesson 23A, Electrical Terms and Basic Electricity - 2. A device, such as a circuit breaker, that clears a fault when current rises past its limit.
Lesson 23B, Grounding, Bonding and the Electrical Service - 3. A device such as a circuit breaker or a fuse.
Lesson 24A, Service Equipment, Enclosures and Panelboards - 4. A fuse or circuit breaker that stops the flow of electricity on an overcurrent or a short circuit.
Lesson 24B, Overcurrent Protection, GFCI and AFCI - 5. A circuit breaker or fuse that interrupts current above its rating.
Lesson 24C, Panelboard Defects, Subpanels and Problem Panels - 6. The device protecting a circuit from overcurrent; for a condenser, its maximum rating is on the condenser label.
Lesson 28B, Cooling Systems: Inspecting Equipment and Typical Defects - Overfiring
- A stove fire that burns too hot.
Lesson 40B, Draft Problems, Fireplace Inserts, Wood and Pellet Stoves - Overflow
- 1. An opening near the top of a bathtub, above the drain, piped to the fixture drain through a tee fitting.
Lesson 35A, Bathtubs - 2. An opening high in a bathroom sink basin, opposite the faucet, joined to the drain outlet.
Lesson 35C, Sinks - Overflow pan
- A pan under the evaporator coil, at least 1-1/2 inches deep and extending past the coil by at least 3 inches on all sides.
Lesson 28C, Cooling Systems: Condensate, Line Sets and Thermostats - Overflow tube
- The tube that carries water into the bowl when the fill valve malfunctions.
Lesson 35D, Toilets and Bidets - Overfusing
- Protecting a circuit with a fuse rated larger than the circuit allows.
Lesson 24B, Overcurrent Protection, GFCI and AFCI - Owner's representative
- The person acting for the property owner, usually a real estate agent, with the listing agent preferred.
Lesson 19C, Deficient Conditions, Service Life and Imminent Threats - Oxidation
- A reaction similar to rust that aluminum tends toward; on a wire it raises resistance at connections.
Lesson 25B, Older Wiring: Knob and Tube, Cloth NM and Aluminum - Oxygen barrier
- A layer, such as the aluminum in PEX-AL-PEX, that keeps oxygen from passing through tubing into the water.
Lesson 34B, Pipe Supports, Copper, CPVC, Galvanized Steel and PEX - Oxygen-depletion safety system
- A safety system mandatory on unvented appliances.
Lesson 31B, Floor and Wall Furnaces, Room Heaters and Unvented Appliances
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