How to Read a Home Inspection Report: A Plain-English Glossary

Home inspection reports use shorthand from electrical, plumbing, HVAC, structural, and roofing trades that goes mostly unexplained. The terms cluster around a few high-stakes patterns: obsolete or hazardous wiring (knob-and-tube, aluminum branch wiring, Federal Pacific panels, double-taps), problematic plumbing materials (galvanized supply, polybutylene, lead service lines), HVAC age and efficiency indicators (SEER, AFUE, refrigerant type), and moisture or foundation signals (efflorescence, settlement, heaving, hairline vs. structural crack). This glossary covers the terms that drive most negotiation and most worry. Knowing them turns a confusing report into a triagable list.

Electrical terms

Knob-and-tube wiring

Pre-1950s wiring system using porcelain insulators (knobs) and protective tubing (tubes). Functional when undisturbed, but it has no grounding and gets brittle with age. Most insurance carriers will not write a policy on a home with active knob-and-tube circuits. If found, expect to budget $8,000-15,000 for partial replacement or $15,000-40,000 for whole-house rewire depending on accessibility.

Aluminum branch wiring

Common in homes built 1965-1973 as a copper substitute. Aluminum oxidizes at connection points, creating high resistance and fire risk. Mitigation isn't full rewire (typically) — it's installation of approved pigtail connectors (CO/ALR or COPALUM) at every outlet, switch, and panel termination. Mitigation cost: $1,500-4,000 for a typical home. Often required by insurance.

Federal Pacific Stab-Lok, Zinsco, Challenger panels

Three brands of electrical panels with documented failure-to-trip issues. Federal Pacific Stab-Lok panels are the most flagged. These panels won't reliably trip on overcurrent, creating fire risk. Most insurance carriers require replacement; even if not required, replacement is recommended. Cost: $1,500-3,500 for panel replacement.

Double-tap

Two conductors connected under a single breaker terminal designed for one. Code violation; creates loose-connection risk. Fix: install a tandem breaker if panel allows, or run one of the circuits to a different breaker. Cheap fix ($150-300 by an electrician) but indicates the panel was modified by a non-professional.

GFCI / AFCI

GFCI (Ground Fault Circuit Interrupter) is the outlet type required in wet areas — kitchens, bathrooms, garages, exterior — that trips on minor leakage to ground. AFCI (Arc Fault Circuit Interrupter) is a breaker type that detects arcing faults; required by current code on most living-area circuits. Missing GFCI/AFCI in required locations is a common safety-tier finding. Replacement cost: $20-40 per outlet/breaker, $150-400 in labor for a few.

Plumbing terms

Galvanized supply pipe

Common in homes pre-1960. Steel pipe coated with zinc. The coating wears out from inside, reducing flow over decades and contributing to discolored water. Eventually requires full replacement with copper or PEX. Cost: $4,000-15,000 for a typical home re-pipe.

Polybutylene

Gray plastic supply pipe installed 1978-1995, subject to class-action settlements due to widespread fitting failures. Tends to fail catastrophically, often without warning. Most insurance carriers will not write a policy on homes with polybutylene supply lines. Replacement cost: $4,000-12,000.

Lead service line

The line from the city water main to your house. Lead service lines are most common in cities with pre-1940 water infrastructure (Chicago, Detroit, parts of the Northeast). Replacement is increasingly required by local ordinance; many cities offer subsidies. Cost: $3,000-10,000 if the owner is responsible for the full line.

PEX vs. copper

PEX (cross-linked polyethylene) is the modern standard for residential supply lines — flexible, freeze-resistant, easier to install, cheaper than copper. Copper is the traditional standard, slightly more durable. Either is fine; neither is a flag.

HVAC terms

SEER, AFUE

SEER (Seasonal Energy Efficiency Ratio) measures AC efficiency; higher is better. New units are typically 14-22 SEER. A unit at 8-10 SEER is at least 15-20 years old and inefficient. AFUE (Annual Fuel Utilization Efficiency) measures furnace efficiency; 80% AFUE is standard older-unit, 95%+ is modern condensing. Both are good age proxies and replacement-runway signals.

R-22 refrigerant

Older AC refrigerant phased out under the Montreal Protocol. Production banned in the US since 2020. Units running R-22 still work, but recharge costs run $100+/lb when even available. R-22 units flagged at inspection are end-of-life; budget replacement within 1-3 years.

Heat exchanger crack

Crack in the metal component that separates combustion gases from circulated air in a furnace. Allows carbon monoxide into the home. Furnace must be replaced (not repaired). Cost: $3,500-7,000 depending on size and type. Safety-tier finding always.

Structural and moisture terms

Hairline crack vs. structural crack

Hairline cracks (under 1/16 inch wide) in foundation walls or slabs are usually normal concrete curing and settlement. Structural cracks (wider than 1/8 inch, horizontal, stair-step, or accompanied by displacement) indicate movement and warrant structural engineer evaluation. The direction matters: vertical cracks are usually less concerning than horizontal; horizontal cracks in foundation walls indicate hydraulic pressure from outside.

Efflorescence

White crystalline deposit on masonry or concrete, especially in basements. Indicates water has migrated through the masonry, carrying minerals to the surface. Not structurally harmful in itself but signals an active moisture path — and where moisture goes, mold can follow. Investigation of the moisture source is the actual action item.

Settlement vs. heaving

Settlement is the foundation moving downward (gravity, soil compression, water table changes). Heaving is foundation moving upward, usually from expansive clay soils or frost. Both can indicate underlying soil issues. Severity depends on rate of movement — slow settlement over decades is usually tolerable; recent or accelerating movement requires intervention.

Mansard, gable, hip

Roof shapes. Mansard: four-sided with steep lower slopes (common in older Victorian or French-influenced homes). Gable: classic triangular ends. Hip: sloped on all four sides without vertical ends. Affects roofing cost (more complex shapes cost more to replace) and certain insurance ratings (hip roofs are more wind-resistant and may get discounts in hurricane regions).

Roof terms

3-tab vs. architectural shingle

3-tab asphalt shingles are the older, thinner style — 20-25 year lifespan. Architectural (also called dimensional or laminate) shingles are thicker, more wind-resistant, and warrantied for 30-50 years. Architectural is the current standard for new roofs; finding 3-tab usually indicates an older roof.

Flashing

Metal pieces sealing the joints between the roof and any penetration (chimney, vent stack, skylight) or wall (siding-to-roof transition). Most roof leaks happen at flashing, not at the field of the roof. Damaged or improperly installed flashing is a common inspection finding.

Soft spots, sagging, granule loss

Soft spots underfoot during a roof walk indicate decking damage from prolonged water intrusion. Sagging indicates structural failure of rafters or sheathing. Granule loss on shingles (visible as bare spots or accumulated granules in gutters) signals the shingle is past its useful life. Any of these in combination usually mean roof replacement is near.

Frequently asked questions

Frequently asked

Should I worry about every code violation in the inspection report?

No. Inspectors often note items installed under older codes that aren't current-code compliant. Older homes are typically grandfathered — you're not required to bring everything up to current code. The report flags the discrepancies so you know; the actionable subset is what's a safety hazard or what's required by your insurance carrier.

What does "recommended for further evaluation by qualified specialist" mean?

The inspector saw something they think warrants deeper investigation by a specialist (structural engineer, licensed electrician, HVAC tech, foundation contractor). It's typically the inspector hedging — they're saying "this might be significant; I'm not qualified to tell you how significant." Schedule the specialist evaluation; don't ignore it.

My report uses different severity terms than what you describe. How do I decode them?

Most inspectors use a three-tier system regardless of the specific labels. Look for the inspector's legend (usually in the first few pages of the report) that defines what their severity tags mean. The mapping to safety/major/minor is almost always clean once you identify the inspector's terminology.

How long does a home inspection usually take?

Two to four hours for a typical single-family home, plus another hour for the closing walkthrough with the buyer. Report turnaround is typically 24-48 hours. Inspectors who do an entire inspection in under 90 minutes are likely cutting corners; ask which areas they accessed (attic, crawlspace, roof) when reviewing the report.

Are inspector recommendations legally binding for sellers?

No. The inspection report identifies issues; what the seller is obligated to do depends on contract language and any subsequent negotiation. The report is a tool for the buyer's decision-making and negotiation, not a legal claim against the seller. Seller-disclosure obligations are a separate legal matter.