National Home Inspector Examination cheat sheet

Long horizontal cracks in a masonry or concrete foundation wall indicate lateral soil pressure or frost heave; narrow vertical cracks are more often shrinkage.

Notches in solid-lumber floor joists may not exceed 1/6 of the joist depth and are not allowed in the middle third of the span; bored holes may not exceed 1/3 of the depth.

Wood joists require at least 1-1/2 inches of bearing on wood or metal and 3 inches of bearing on masonry.

Crawlspace clearances: 18 inches beneath floor joists, 12 inches beneath girders, and 24 inches clear at the access opening.

Cutting, notching, or boring an engineered truss in the field requires written approval from a design professional.

Diagonal cracks radiating from the corners of door and window openings usually indicate differential foundation movement.

Wood framing in contact with concrete or soil must be pressure-treated or separated by an impermeable moisture barrier.

Stud notching is limited to 25 percent of the stud depth; bored holes may not exceed 40 percent of the depth.

Furnace temperature rise is the supply-to-return air temperature difference and must fall within the data-plate range, commonly about 35-65 degrees F for gas units.

A properly operating central air conditioner produces roughly a 15-20 degree F difference between return and supply air.

The suction (large) refrigerant line must be insulated; the liquid (small) line is normally not insulated.

Condensate lines need a trap; the primary drain must not discharge into a crawlspace, and the secondary pan drain should terminate where overflow is visible.

Combustion air by indoor infiltration requires about 50 cubic feet of space per 1,000 BTU/h of appliance input.

Return air may not be drawn from a garage, bathroom, kitchen, or unconditioned space.

A cracked heat exchanger is a safety hazard because flue gases can enter the supply air stream.

Heat pumps move heat rather than generate it, so auxiliary resistance heat operating during defrost and cold weather is normal.

Dryer ducts must be smooth-walled, as short and straight as practical, and terminate outdoors with a backdraft damper.

Copper conductor ampacities: 14 AWG = 15 A, 12 AWG = 20 A, 10 AWG = 30 A.

GFCI protection is required in bathrooms, kitchens, garages, outdoors, unfinished basements, crawlspaces, and within 6 feet of a sink.

In a subpanel the neutral bus must be isolated from ground; the main bonding screw is used only at the service panel.

Receptacle spacing: no point on a wall may be more than 6 feet from a receptacle, and any wall space 2 feet or wider requires one.

Service-drop clearances: 10 feet above grade or walkways, 12 feet above a driveway, and 3 feet from an openable window.

A double-tapped breaker is improper unless the breaker is listed for two conductors.

Junction boxes must remain accessible; splices may not be buried in walls or ceilings.

AFCI protection is required on branch circuits serving bedrooms under modern code cycles.

Aluminum branch-circuit wiring is a fire concern and requires evaluated connections or replacement.

A TPR valve relief pipe must terminate within 6 inches of the floor, be full size, unthreaded, untrapped, and have no valve in it.

Drain slope: 1/4 inch per foot for pipe 2 inches and smaller; 1/8 inch per foot for 3 inches and larger.

Residential supply pressure should be 40-80 psi; a pressure-reducing valve is needed above 80 psi.

Each fixture requires a trap, and the trap arm may not exceed the distance allowed to its vent.

A dielectric union or plastic fitting is required where copper meets galvanized steel to prevent galvanic corrosion.

A water heater needs a TPR valve and discharge pipe, and often an expansion tank on a closed system.

Vent terminals must extend above the roof and be located away from windows, doors, and air intakes.

A backwater valve on the sewer line protects the basement from reverse flow during surcharge.

A chimney must extend at least 3 feet above the roof at the penetration and 2 feet above anything within 10 feet.

No more than two layers of asphalt shingles may remain on a roof; adding a third layer requires stripping the existing roofing.

Asphalt shingles require a minimum slope and special underlayment between 2:12 and 4:12; below 2:12 a membrane roof system is required.

Step flashing is installed at roof-to-sidewall intersections, with kick-out flashing at the bottom to divert water away from the wall.

Ice-dam protection membrane is required along eaves in cold climates and extends at least 24 inches inside the exterior wall line.

An open valley is lined with metal; a closed or woven valley conceals the flashing beneath the shingles.

Shingle fasteners must penetrate the sheathing at least 3/4 inch, with placement following the manufacturer's nailing pattern.

Attic ventilation is 1/150 of the attic floor area, or 1/300 where a vapor retarder is present.

Ground should slope at least 6 inches away from the foundation over the first 10 feet.

Siding should be at least 6 inches above finished grade and 1 inch above a roof surface.

Guardrail openings must not allow a 4-inch sphere to pass; residential deck guards are at least 36 inches high.

Handrails on stairs are 34-38 inches above the nosing.

Stair risers may not exceed 7-3/4 inches and treads must be at least 10 inches deep.

A deck ledger must be attached to the band joist with lag screws or through-bolts, flashed, and not attached through siding.

Downspouts should discharge away from the foundation; gutters generally need one downspout per 30-40 feet of run.

Decay is most likely at wood-to-ground contact, deck posts, sill plates, and masonry below grade.

Smoke alarms are required inside each bedroom, outside each sleeping area, and on every story.

The garage-to-house wall requires 1/2-inch gypsum board, and the door must be self-closing and solid-core or 20-minute rated.

Egress windows need at least 5.7 square feet of clear opening, 24 inches of height, 20 inches of width, and a sill no more than 44 inches above the floor.

Stairways must be at least 36 inches wide with 6 feet 8 inches of headroom.

Attic access openings must be at least 22 by 30 inches.

Safety glazing is required where glass is near a door, beside a stairway, or has a low sill height.

Cracks at drywall corners and above door openings usually relate to framing shrinkage or minor movement rather than structural failure.

Floor slope is measured and reported; a slope steeper than about 1 inch in 20 feet warrants further investigation.

The vapor retarder goes on the warm side: interior in cold climates, exterior side in hot-humid climates.

Bath and kitchen exhaust fans must discharge outdoors, never into an attic or crawlspace.

Attic insulation must not block eave vents; baffles maintain a clear air channel from the soffit.

Recessed lights in an insulated ceiling must be IC-rated and sealed to limit air leakage.

A crawlspace should have a 6-mil vapor retarder over the soil, lapped and turned up the walls.

Typical insulation targets are R-38 to R-49 in attics and R-13 to R-21 in walls, depending on climate zone.

A blower-door test measures air leakage in air changes per hour at 50 pascals (ACH50).

Combustion appliances can backdraft when exhaust fans depressurize the house; test with the appliance and fans running.

The standard inspection is visual and limited to readily accessible systems; it is not technically exhaustive or destructive.

Reports should state the observed condition, its implication, and a recommended action rather than only listing defects.

Inspectors should not state that a component 'meets code'; they report performance and safety concerns instead.

Performing repairs on a property inspected within the past 12 months is prohibited in many jurisdictions.

The inspection agreement should state scope, limitations, fee, and any dispute-resolution clause.

Photographs, model and serial numbers, and moisture readings support findings and reduce liability.

Inspectors must maintain client confidentiality and disclose any conflict of interest.

Any system not operated because of weather or safety concerns must be identified in the report as not inspected.