Home inspection glossary
Plain-English definitions of the terms that show up in inspection reports — what they mean, why they matter on site, and how to explain them to a client without overstating the finding.
AFCI
An arc-fault circuit interrupter is a breaker that opens the circuit when it detects the electrical signature of arcing, which is a common ignition source in residential fires.
Aluminum branch circuit wiring
Solid aluminum wiring used for 15- and 20-amp branch circuits in many homes built between roughly 1965 and 1973, associated with an elevated risk of overheating at connections.
ASHI
The American Society of Home Inspectors, a membership organisation that publishes a widely referenced Standard of Practice and Code of Ethics for home inspectors.
Backdrafting
A condition where combustion gases from a furnace, water heater or fireplace spill back into the living space instead of venting outside.
Backflow prevention
A device or design feature that stops contaminated water from being drawn backwards into the potable water supply.
Bonding
Connecting metallic components of a building's systems together so they remain at the same electrical potential, reducing shock hazard.
Building envelope
The physical separation between the conditioned interior and the outdoors, comprising the roof, walls, windows, doors, floors and foundation.
Crawl space encapsulation
Sealing a crawl space with a heavy vapour barrier over the ground and up the walls, usually combined with insulation, air sealing and humidity control.
Cross-connection
Any point where the potable water supply can come into contact with a source of contamination.
Deficiency
A condition that is not performing as intended, is unsafe, or is at the end of its service life — the general term many report forms use for a reportable finding.
Double-tapped breaker
Two conductors terminated under a single breaker lug that is listed for only one conductor.
Drip edge
Metal flashing installed along roof eaves and rakes that directs runoff into the gutter and away from the fascia and sheathing.
Efflorescence
The white, powdery mineral deposit left on masonry when water passes through it and evaporates at the surface.
EIFS
Exterior Insulation and Finish System, a multi-layer synthetic stucco cladding that has been associated with moisture intrusion when installed without drainage.
Federal Pacific Stab-Lok panel
An electrical panel brand widely installed from the 1950s to the early 1980s whose breakers have been reported to fail to trip under fault conditions.
Flashing
Sheet material installed at joints and transitions in the building envelope to direct water away from vulnerable intersections.
Four-point inspection
A limited insurance inspection of the roof, electrical, plumbing and HVAC systems, most commonly required in Florida for older homes.
GFCI
A ground-fault circuit interrupter, a device that cuts power when it detects current leaking to ground, protecting people from electric shock.
Grading
The slope of soil around a structure, which should fall away from the foundation to carry surface water off.
Header
A beam spanning an opening in a load-bearing wall that carries the loads above it to the framing on either side.
Heat exchanger
The metal partition in a fuel-burning furnace that transfers heat to the air stream while keeping combustion gases separate from it.
Ice dam
A ridge of ice at a roof eave, formed when heat escaping into the attic melts snow that then refreezes over the colder overhang.
InterNACHI
The International Association of Certified Home Inspectors, a large membership body providing certification, training and a published Standards of Practice.
Knob-and-tube wiring
An early wiring method using ceramic knobs and tubes to support single insulated conductors, common in homes built before about 1950.
Material defect
A condition that significantly affects the value, desirability, habitability or safety of a property — the reporting threshold used by many standards and state statutes.
Negative grade
Ground that slopes toward a building rather than away from it, directing surface water at the foundation.
NPMA-33
The standard Wood Destroying Insect Inspection Report form published by the National Pest Management Association, often required for VA and other loans.
Orangeburg pipe
A bituminised fibre drain pipe used for sewer laterals from the 1940s to the 1970s that deforms and collapses with age.
Polybutylene piping
Flexible grey or blue plastic water supply piping installed in many homes from roughly 1978 to 1995, associated with a high rate of failure at fittings.
Pre-listing inspection
An inspection commissioned by a seller before a property goes on the market.
Radon
A naturally occurring radioactive gas that enters buildings from the soil and is a recognised cause of lung cancer.
Ridge vent
A continuous vent along the roof ridge that exhausts attic air, working with soffit vents to ventilate the attic.
S-trap
An obsolete drain trap configuration that can siphon its own water seal, allowing sewer gas into the building.
Sewer scope
A camera inspection of the buried drain line running from the house to the municipal main or septic tank.
Spalling
Flaking, chipping or delamination of a concrete or masonry surface, usually driven by freeze-thaw cycling or corroding embedded steel.
Standard of Practice
The published document defining what a home inspection includes, what it excludes, and how the inspector reports findings.
TPR valve
The temperature and pressure relief valve on a water heater, which discharges if temperature or pressure exceeds safe limits.
Truss uplift
Seasonal arching of roof trusses that opens a gap between interior partition walls and the ceiling, usually in winter.
Vapour retarder
A material that slows the diffusion of water vapour through an assembly, used to keep moisture from condensing inside walls, floors or ceilings.
Weep holes
Small openings at the base of a masonry veneer that let water that has penetrated the veneer drain back out.
Wind mitigation inspection
An insurance inspection documenting construction features that reduce a building's vulnerability to windstorm damage, most commonly performed in Florida.
Zinsco panel
An electrical panel brand from the 1950s to 1970s with reported failures of breakers to trip and of breakers to seat reliably on the bus.