Glossary of Terms

At Arrow Home Inspections, we believe that education empowers better decision-making. Whether you’re a first-time buyer, a seasoned homeowner, or preparing to sell, understanding the terms used in your home inspection is key to feeling confident and informed.

Home inspection reports can include industry-specific language and technical references that may not be familiar to everyone. That’s why we’ve included this glossary—to help demystify the process and clearly communicate what we see, so you can take action with clarity.

Below are some common terms used during inspections and what they mean, explained in plain language.

AFCI (Arc Fault Circuit Interrupter) – A type of circuit breaker that shuts off electricity when it detects an arc fault, reducing the risk of fire.

Air Admittance Valve (AAV) – A one-way valve used in plumbing to allow air into the drain system without needing a full vent pipe.

Anti-Scald Device – A safety valve that limits hot water temperature to prevent burns.

Asbestos – A heat-resistant mineral fiber once used in building materials. Can be hazardous if disturbed. Found in insulation, tiles, siding, and more.

Attic Hatch – The entry point to an attic space, which should be insulated and sealed for energy efficiency.

Balloon Framing – An old construction style where wall studs run continuously from foundation to roof, common before 1930.

Baseboard Heat – A type of heating system that radiates heat from baseboards along walls, either electric or hydronic.

Beam – A horizontal structural member that supports loads across an open space.

Breaker Panel – The box containing circuit breakers (or fuses in older homes) that control and protect a home’s electrical circuits.

BX Cable – An older type of armored electrical wiring with a metallic sheath.

Cast Iron Pipe – A heavy, durable drainpipe material common in older homes. Can rust or crack over time.

Circuit Breaker – A switch that automatically turns off electrical flow during a fault to prevent overheating or fire.

Collar Tie – A horizontal framing member in the upper third of the roof that resists outward thrust from the rafters.

Concrete Block Foundation – A common modern foundation made of stacked concrete masonry units.

Copper Pipe – A durable metal piping commonly used for water supply lines.

Crawl Space – A shallow area under a home used for access to mechanicals. May require insulation and moisture control.

Cripple Wall – A short wall between the foundation and first-floor framing. Can be vulnerable in earthquakes.

Drip Loop – A downward curve in overhead electrical wires before entering the home to prevent water from entering the conduit.

Ductwork – Metal or flexible tubes that deliver conditioned air throughout a home.

Electrical Service Drop – The overhead or underground wires that bring electricity from the utility to the home.

Fieldstone Foundation – Made of irregular stones and mortar. Common in historic homes, but more prone to water issues and shifting.

Flashing – A thin material used to prevent water intrusion at roof joints, windows, and doors.

Forced Air – A heating or cooling system that uses ducts and a blower to move air through the home.

Furnace – A heating appliance that warms air and circulates it through the home via ducts.

GFCI (Ground Fault Circuit Interrupter) – A safety outlet that shuts off power if it detects a difference in current, typically used near water.

Granite Foundation – Durable stone foundations found in older or upscale homes. Requires maintenance at joints.

Gravity Heat – An old heating method that uses natural convection without fans or pumps to distribute warm air.

Header – A beam placed over a window or door opening to support structural loads.

Joist – Horizontal framing members that support floors or ceilings.

Knob and Tube Wiring – An obsolete electrical system using ceramic knobs and tubes. Can pose a fire risk if not updated.

Lally Column – A round steel column filled with concrete, used to support beams. Preferred over adjustable screw jacks.

Main Disconnect – The primary shut-off for electrical power in the home, typically located in the breaker panel.

Mini-Split System – A ductless heating and cooling system with indoor and outdoor components.

PEX Pipe – Flexible plastic piping used for water supply, resistant to freezing and easy to install.

Pilot Light – A small gas flame that stays lit to ignite the burner in older gas appliances.

Plenum – The central air distribution box in a forced air system, often located above or below the furnace.

Pointing – The process of renewing mortar between masonry units in a foundation or wall.

PVC Pipe – Lightweight plastic piping used in drain, waste, and vent systems.

Radiant Floor Heating – A system where hot water or electric coils heat the floor, offering even heat distribution.

Rafters – Sloped framing members that support a roof’s surface.

Receptacle – Another term for an electrical outlet.

Return Register – The vent that draws air back into a forced-air heating or cooling system.

Romex (NM Cable) – A type of plastic-sheathed electrical cable used in modern homes.

Seismic Strap – Metal bands used to secure water heaters and other heavy appliances to walls in seismic zones.

Service Panel – The main distribution point for a home’s electrical system, housing breakers or fuses.

Sewer Ejector Pump -  A pump used to move wastewater from lower levels (like basements) up to the main sewer or septic line when gravity alone can’t do the job. Common in homes with bathrooms or laundry rooms in the basement and below the main drain line. 

Shut-Off Valve – A valve that stops water or gas flow to a fixture or appliance.

Slab Foundation – A foundation made of poured concrete, typically without a basement or crawlspace.

Solid Aluminum Wiring – Found in some 1960s–70s homes. Considered a fire hazard and often replaced.

Steam Radiator – A cast iron unit that delivers heat from a steam system, common in older homes.

Sump Pump – A pump used to remove water from a basement or crawl space.

Thermal Seal Failure – When the seal between glass panes in a window or door fails, leading to fogging or condensation.

TPRV (Temperature and Pressure Relief Valve) – A safety valve on a water heater that opens if temperature or pressure gets too high.

Truss – A prefabricated triangular framing unit used in roofs to distribute load across exterior walls.

Vapor Barrier – A material that prevents moisture from entering walls, ceilings, or floors.

Vermiculite – A type of attic insulation. If installed before 1990, it may contain asbestos and should be tested.

Water Hammer – A loud banging sound caused by sudden water flow stopping in plumbing.

Water Heater – A tank or on-demand appliance that heats water for household use.

Wattage Rating – The maximum electrical load a component or circuit can safely handle.

Weatherhead – The cap where overhead electrical wires enter the home. Must be sealed to prevent water intrusion.

Weep Holes – Small openings at the bottom of windows or brick walls to allow water to escape.