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National Home Inspector Examination practice questions

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First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

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Question 1Structural Systems

The primary purpose of a foundation footing is to do which of the following?

  1. Spread the building load over a larger area of soil Correct answer.
  2. Anchor the roof structure to the walls
  3. Provide a finished surface for a basement floor
  4. Support the exterior wall siding

Explanation

A footing is the widened concrete base at the bottom of a foundation. It transfers the concentrated load of the foundation wall or column to the soil over a larger bearing area, keeping soil pressure within acceptable limits.

Question 2Structural Systems

In platform framing, the subfloor panels are fastened directly to the...

  1. Wall studs
  2. Floor joists Correct answer.
  3. Ceiling joists
  4. Rafters

Explanation

Platform framing builds each floor as a platform, with subfloor sheathing nailed or screwed to the floor joists. The wall frames for the next level are then erected on top of that platform.

Question 3Structural Systems

In a gable roof, the rafters normally meet at the...

  1. Ridge Correct answer.
  2. Soffit
  3. Fascia
  4. Eave

Explanation

The ridge is the highest horizontal line of a gable roof, where opposing rafters meet. The eave is the lower edge, the fascia covers the rafter tails, and the soffit is the underside of the overhang.

Question 4Structural Systems

A header is installed over a wall opening in order to...

  1. Support the siding above the opening
  2. Keep the wall studs plumb
  3. Provide a nailing surface for interior trim
  4. Carry loads from above the opening to the adjacent framing Correct answer.

Explanation

A header, also called a lintel in masonry, is a beam that spans an opening and transfers loads from above to the jack studs or adjacent wall framing. It is sized for the span and the load it carries.

Question 5Structural Systems

In wood-frame construction, the sill plate is the...

  1. Vertical member at the corner of a wall
  2. Lowest rafter in a roof
  3. Horizontal member resting on the foundation and supporting the wall framing Correct answer.
  4. Beam that supports the second floor

Explanation

The sill plate, or mudsill, is the horizontal wood member anchored to the top of the foundation. Exterior wall framing is erected on and fastened to this plate.

Question 6Structural Systems

A standard on-center spacing for floor joists in residential construction is...

  1. 4 inches
  2. 48 inches
  3. 16 inches Correct answer.
  4. 30 inches

Explanation

Floor joists are commonly spaced at 12, 16, or 24 inches on center, with 16 inches being the most common. Sheathing and finish flooring are dimensioned to match those spacings.

Question 7Structural Systems

Stair-step cracks that follow the mortar joints in a brick foundation wall most often indicate...

  1. Excess moisture in the mortar
  2. Ordinary drying shrinkage
  3. Movement or differential settlement Correct answer.
  4. A defective roof covering

Explanation

Stair-step cracking follows the weaker mortar joints as one part of the foundation moves relative to another. This pattern is a classic sign of differential settlement or other foundation movement.

Question 8Structural Systems

Roof trusses should be modified in the field only when...

  1. The changes are minor
  2. The alteration is approved by a qualified design professional Correct answer.
  3. The attic is inaccessible
  4. The roof pitch is low

Explanation

Trusses are engineered as a system, and cutting or adding members can change the load paths. Any field alteration should be reviewed and approved by a qualified design professional.

Question 9Structural Systems

When a hole is bored through a solid wood floor joist, the hole should be located...

  1. In the middle third of the joist depth Correct answer.
  2. Within 2 inches of the top edge
  3. Within 2 inches of the bottom edge
  4. At the joist end bearing point

Explanation

Bored holes are limited in size and must stay away from the top and bottom edges, where bending stresses are highest. The central portion of the joist depth is the appropriate location for a hole.

Question 10Structural Systems

A horizontal crack near the middle of a concrete basement wall is most commonly caused by...

  1. Freeze-thaw action in the wall
  2. Settlement of the footing
  3. Lateral soil and backfill pressure Correct answer.
  4. Corrosion of reinforcing steel

Explanation

Backfill and saturated soil exert lateral pressure against a basement wall, producing bending stress that peaks near mid-height. Horizontal cracking in that zone is a common result, especially if the wall is under-reinforced or backfilled too early.

Question 11Structural Systems

A deck ledger board attached to a house should be...

  1. Resting directly on the ground
  2. Supported by a pier at midspan
  3. Nailed only to the siding
  4. Flashed and securely bolted to the house framing Correct answer.

Explanation

The ledger transfers the deck load to the house structure, so it must be attached to framing with approved bolts or lag screws and protected with flashing. Attaching it only to siding or trim does not provide adequate strength.

Question 12Structural Systems

In balloon framing, firestopping is required at each floor line because...

  1. The floor joists are exposed to the attic
  2. The roof is unsupported at the eaves
  3. The wall cavities form continuous vertical channels Correct answer.
  4. The studs are shorter than in platform framing

Explanation

Balloon framing uses continuous studs that run from the sill to the eaves, leaving uninterrupted stud bays. Firestopping at floor levels blocks the vertical chimney effect that would otherwise spread fire quickly.

Question 13Structural Systems

A collar tie in a roof frame connects...

  1. Opposing rafters near the ridge Correct answer.
  2. The ridge board to the chimney
  3. Ceiling joists to the ridge board
  4. Rafters to the top plate

Explanation

Collar ties are horizontal members installed between opposing rafters, usually in the upper third of the roof. They help resist rafter separation and wind uplift.

Question 14Structural Systems

Cracks in a concrete slab-on-grade caused by drying shrinkage usually appear...

  1. As wide openings at the slab edge
  2. Parallel to the foundation walls
  3. Only at the perimeter
  4. In a random pattern and are not continuous Correct answer.

Explanation

Shrinkage cracks form as concrete cures and loses moisture, and they typically occur in a random pattern. They are usually narrow and do not show the continuity or offset typical of structural movement.

Question 15Structural Systems

A wood girder in a crawlspace that bears on a concrete pier should have...

  1. A layer of gravel under the pier
  2. A moisture barrier or termite shield between the wood and concrete Correct answer.
  3. No contact with the pier
  4. A coat of paint on the end

Explanation

Concrete can wick moisture into wood, and termites can tunnel through concrete to reach it. A capillary break or termite shield separates the materials and helps protect the girder.

Question 16Structural Systems

The maximum allowable notch in the top edge of a floor joist at a bearing point is typically...

  1. One-quarter the joist depth Correct answer.
  2. One-half the joist depth
  3. One-third the joist depth
  4. Three-quarters the joist depth

Explanation

At a bearing point, a notch is limited to one-quarter of the joist depth. Notching removes material from the tension or compression zone and reduces the joist's capacity.

Question 17Structural Systems

When a floor opening is cut for a stairway, the opening must be framed with...

  1. A layer of subfloor
  2. Trimmer joists and a header Correct answer.
  3. A single blocking piece
  4. A doubled sole plate

Explanation

Cutting joists for a stair opening interrupts their span, so the cut ends must be carried by a header. Trimmer joists run alongside the opening to support the header and adjacent floor framing.

Question 18Structural Systems

An anchor bolt in a wood-frame house is used to...

  1. Fasten the roof sheathing
  2. Connect the sill plate to the foundation Correct answer.
  3. Secure the subfloor to the joists
  4. Tie the rafters to the ridge

Explanation

Anchor bolts are embedded in the foundation and extend through the sill plate, tying the wood frame to the concrete. This connection resists uplift and lateral forces such as wind and earthquakes.

Question 19Structural Systems

A diagonal crack that runs from the corner of a door opening toward the ceiling in a plaster wall is most likely caused by...

  1. Roof truss uplift
  2. Settlement or movement of the foundation Correct answer.
  3. Loose drywall screws
  4. Normal paint shrinkage

Explanation

Diagonal cracks radiating from the corners of openings are a common sign of movement in the structure, often differential foundation settlement. The opening corners concentrate stress, so cracking begins there.

Question 20Structural Systems

The stiffness of a solid wood floor joist is most affected by its...

  1. Depth Correct answer.
  2. Species
  3. Width
  4. Length

Explanation

The bending stiffness of a rectangular member depends on its moment of inertia, which increases with the cube of its depth. Increasing depth is therefore far more effective than increasing width.

Question 21Structural Systems

A two-story wood-frame house has a 2x8 floor joist spanning 12 feet. If the same load is carried by a 2x10 at the same span, the 2x10 will...

  1. Deflect less because its depth is greater Correct answer.
  2. Deflect less only if its width is increased
  3. Deflect the same because the span is unchanged
  4. Deflect more because it is heavier

Explanation

Deflection is inversely related to the moment of inertia, and for a rectangular joist that property rises rapidly with depth. A 2x10 is deeper than a 2x8, so under the same load and span it deflects less.

Question 22Structural Systems

A masonry wall with a lintel over a garage door shows a vertical crack at one end of the lintel. The most likely cause is...

  1. Settlement or insufficient lintel bearing Correct answer.
  2. Excess insulation in the wall
  3. Improper mortar color
  4. Vapor barrier on the wrong side

Explanation

A lintel must have adequate bearing at each end to transfer the wall load to the masonry on either side. If bearing is insufficient or one support settles, the end of the lintel moves and a vertical crack can open at that location.

Question 23Structural Systems

A home inspector finds that a roof rafter has been notched more than one-quarter of its depth at the bearing point. This is a concern because...

  1. It allows water into the attic
  2. It changes the roof pitch
  3. It reduces the member's load-carrying capacity Correct answer.
  4. It prevents proper attic ventilation

Explanation

Notching removes wood from the rafter at a point where it bears on the wall, reducing the effective section. Over-notching can weaken the rafter and lead to sagging or splitting under roof loads.

Question 24Mechanical Systems

What is the function of the temperature and pressure relief valve on a storage water heater?

  1. It relieves excess pressure or temperature. Correct answer.
  2. It prevents backflow into the cold supply.
  3. It drains the tank during servicing.
  4. It mixes cold water into the hot outlet.

Explanation

The T&P valve is a safety device that opens when tank pressure or water temperature exceeds its rating, preventing a tank rupture or steam explosion. It is not a service drain and does not blend or block water flow.

Question 25Mechanical Systems

Where is the air filter normally located on a forced-air furnace system?

  1. Inside the flue connector
  2. In the supply plenum above the furnace
  3. At the return air inlet to the blower Correct answer.
  4. On the outdoor condenser cabinet

Explanation

The filter must clean air before it reaches the blower and the indoor coil, so it is placed on the return air side of the system. Placing it downstream would leave the blower and coil exposed to dirt.

Question 26Mechanical Systems

In a split-system air conditioner, where is the condenser normally located?

  1. Inside the supply duct
  2. Inside the return plenum
  3. Outdoors, next to the house Correct answer.
  4. In the attic beside the air handler

Explanation

The condenser rejects heat absorbed indoors to the outside air, so it is located outdoors with the compressor. The indoor portion (evaporator coil and blower) sits in the duct system or air handler.

Question 27Mechanical Systems

A gas-fired furnace must have a manual shutoff valve located where?

  1. Outside the building at the service entry
  2. At the gas meter only
  3. Downstream of the burner manifold
  4. Within sight of the appliance Correct answer.

Explanation

Codes require a manual shutoff valve in the same room and within sight of the appliance so gas can be cut off quickly for service or in an emergency. Meter and service-entry valves do not satisfy this appliance-level requirement.

Question 28Mechanical Systems

What is the purpose of return grilles in a forced-air distribution system?

  1. Supply conditioned air to each room
  2. Return room air to the furnace Correct answer.
  3. Relieve excess pressure in the ducts
  4. Exhaust flue gases outdoors

Explanation

A forced-air system is a loop: supply registers deliver conditioned air and return grilles bring room air back to the furnace for reconditioning. Without adequate return air the system is starved and operating pressures rise.

Question 29Mechanical Systems

What does the heat exchanger in a gas furnace do?

  1. It filters dust from the return air
  2. It keeps flue gases out of the supply air Correct answer.
  3. It cools supply air before it reaches the rooms
  4. It burns fuel and mixes products with supply air

Explanation

The heat exchanger is a metal barrier: combustion gases pass through it while room air flows across its outside surface. A sound exchanger keeps the two airstreams separate, while a crack allows carbon monoxide into the supply air.

Question 30Mechanical Systems

How does a room thermostat control a furnace?

  1. By regulating manifold gas pressure
  2. By switching the burner on and off Correct answer.
  3. By adjusting blower speed
  4. By measuring flue gas temperature

Explanation

A thermostat senses room temperature and makes or breaks the control circuit to the furnace, starting or stopping the burner and blower. It does not set gas pressure or blower speed, which are adjusted at the appliance.

Question 31Mechanical Systems

A draft hood on a natural-draft gas furnace serves mainly to do what?

  1. Admit dilution air and stop backdraft Correct answer.
  2. Raise the temperature of the flue gases
  3. Seal the flue against downdrafts
  4. Boost the chimney draft

Explanation

The draft hood mixes room air with flue gases, stabilizes draft over varying conditions, and provides an opening where gases can spill rather than back up into the house. It is open to the room, so it cannot seal the vent.

Question 32Mechanical Systems

A sediment trap on a gas appliance connection is installed where?

  1. Between the regulator and the gas meter
  2. Inside the burner manifold
  3. In the drop leg below the appliance tee Correct answer.
  4. At the top of the vertical riser

Explanation

The trap is a capped nipple installed in a vertical drop leg just upstream of the appliance, so debris and pipe dope fall out of the gas stream before reaching the controls. It must be accessible for cleanout.

Question 33Mechanical Systems

A properly operating central air conditioner typically produces a supply-to-return air temperature difference of about how much?

  1. 15 to 20 degrees F Correct answer.
  2. 35 to 40 degrees F
  3. 5 to 8 degrees F
  4. 25 to 30 degrees F

Explanation

A normal split system drops the air temperature roughly 15 to 20 degrees F across the evaporator coil. Much less suggests low charge or low airflow, while much more points to restricted airflow.

Question 34Mechanical Systems

In a split-system air conditioner, the larger insulated line between the coils is the what?

  1. Condensate line
  2. Discharge line
  3. Suction line Correct answer.
  4. Liquid line

Explanation

The suction line carries cool low-pressure vapor from the evaporator back to the compressor and is insulated to prevent condensation and heat gain. The liquid line is smaller and carries condensed refrigerant to the metering device.

Question 35Mechanical Systems

An evaporator coil condensate drain installed in an attic should do what?

  1. Be capped during the cooling season
  2. Drain by gravity to an approved point Correct answer.
  3. Slope back toward the coil
  4. Discharge into the return plenum

Explanation

Condensate must leave the pan under the influence of gravity, pitched continuously downward to a suitable indirect waste or exterior point. Trapping or back-sloping the line causes overflow and water damage.

Question 36Mechanical Systems

A relief valve on a residential hot-water heating boiler is typically set to open at approximately what pressure?

  1. 5 psi
  2. 100 psi
  3. 30 psi Correct answer.
  4. 150 psi

Explanation

Residential hot-water boilers normally operate near 12 to 20 psi and use a relief valve set around 30 psi, matching the working pressure of the boiler and near-boiler components. A higher setting would not protect the system.

Question 37Mechanical Systems

A heat pump enters defrost mode because of what condition?

  1. The indoor coil is too warm
  2. The thermostat is calling for cool
  3. The outdoor coil has frosted over Correct answer.
  4. The compressor is running too hot

Explanation

In heating mode the outdoor coil is the evaporator and can drop below freezing, so frost builds on it and blocks airflow. The defrost control temporarily reverses the refrigerant cycle to melt the frost.

Question 38Mechanical Systems

The anode rod in a tank-type water heater does what?

  1. Filters sediment from the tank
  2. Keeps the tank from freezing
  3. Corrodes instead of the steel tank Correct answer.
  4. Heats the water during peak demand

Explanation

The anode is a sacrificial metal that corrodes preferentially, protecting the steel tank lining from galvanic attack. Once the rod is consumed, the tank itself begins to corrode and leak.

Question 39Mechanical Systems

A single-wall metal vent connector from a gas furnace should run in which direction?

  1. Away from the chimney at any slope
  2. Upward toward the chimney Correct answer.
  3. Downward toward the appliance
  4. Level from the appliance to the chimney

Explanation

Vent connectors must slope upward toward the chimney, typically about 1/4 inch per foot, so flue gases rise and acidic condensate drains toward the chimney rather than back into the appliance.

Question 40Mechanical Systems

A gas furnace installed in a small, tightly sealed closet requires what?

  1. A second gas shutoff valve
  2. A condensate pump
  3. A larger flue connector
  4. A source of combustion air Correct answer.

Explanation

Fuel-burning appliances need a permanent supply of air for combustion and dilution, usually provided by grilles, louvers, or ducts sized to the appliance input. Without it, the burner starves and the flue can spill products of combustion into the space.

Question 41Mechanical Systems

Why must an electric baseboard heater be kept clear of furniture and drapes?

  1. It reduces the heating output of the unit
  2. It allows cold air to enter the wall cavity
  3. It interferes with the room thermostat
  4. Blocked airflow can cause overheating and fire Correct answer.

Explanation

Baseboard heaters rely on free convection, and blocked airflow traps heat in the unit, raising surface and internal temperatures to a hazardous level. Manufacturers specify minimum clearances for this reason.

Question 42Mechanical Systems

On a furnace start-up, the flame rolls out of the burner area when the blower starts. What does this most likely indicate?

  1. A faulty thermostat
  2. A cracked heat exchanger Correct answer.
  3. A restricted air filter
  4. An oversized burner orifice

Explanation

Rollout triggered by blower operation means the pressurized supply air is escaping into the combustion chamber through a defect, typically a cracked heat exchanger or a failed gasket. This is a carbon monoxide hazard and should be reported as a safety issue requiring service.

Question 43Mechanical Systems

A gas furnace with a 100,000 Btu/h input rating and an 80% AFUE delivers how much heat to the house?

  1. 20,000 Btu/h
  2. 80,000 Btu/h Correct answer.
  3. 125,000 Btu/h
  4. 100,000 Btu/h

Explanation

AFUE expresses the fraction of input energy delivered as heat, so output equals input times efficiency: 100,000 x 0.80 = 80,000 Btu/h. The remainder leaves with the flue gases and through jacket losses.

Question 44Mechanical Systems

Which observation most directly shows spillage at a natural-draft furnace draft hood?

  1. Condensate on the vent connector
  2. Warm supply air at the registers
  3. A steady blue burner flame
  4. Flue gases curling out of the hood Correct answer.

Explanation

Spillage is combustion gases escaping at the draft hood instead of rising up the vent, which happens when draft is inadequate. A tester can confirm it with a smoke or flame test at the hood opening.

Question 45Mechanical Systems

On a heat pump system, auxiliary electric resistance heat typically energizes when what occurs?

  1. The system is switched to cooling mode
  2. The heat pump cannot meet the load alone Correct answer.
  3. The outdoor temperature is above 65 degrees F
  4. The thermostat fan is set to ON

Explanation

Backup resistance heat stages on when the heat pump's capacity falls short of the building load, such as during very cold weather or recovery from a setback. It is a heating-mode function that supplements, not replaces, the compressor.

Question 46Mechanical Systems

Superheat is the difference between the actual refrigerant vapor temperature and what other value?

  1. The outdoor ambient temperature
  2. Its boiling point at the measured pressure Correct answer.
  3. The condensing temperature at the coil
  4. The leaving air temperature

Explanation

Superheat measures how far vapor is above its saturation temperature for the pressure being read, confirming that all liquid has boiled off before the compressor. Subcooling, by contrast, compares liquid temperature with the condensing temperature.

Question 47Electrical Systems

What is the minimum vertical clearance for overhead service-drop conductors above a residential driveway?

  1. 18 feet
  2. 10 feet
  3. 12 feet Correct answer.
  4. 8 feet

Explanation

Service-drop conductors must be at least 12 feet above the surface of a residential driveway. Greater clearances such as 18 feet apply over public streets, roads, and alleys.

Question 48Electrical Systems

Ground-fault circuit interrupter protection is required for receptacles installed in which of these locations?

  1. A dining room
  2. A hallway
  3. A garage Correct answer.
  4. A bedroom

Explanation

Receptacles in garages and accessory buildings require GFCI protection because of the damp, unfinished environment and presence of tools and vehicles. Dining rooms, bedrooms, and hallways are not among the locations where GFCI protection is required for general receptacles.

Question 49Electrical Systems

Which copper conductor size is the minimum permitted for a 20-ampere general-purpose branch circuit?

  1. 12 AWG Correct answer.
  2. 16 AWG
  3. 10 AWG
  4. 14 AWG

Explanation

A 20-ampere circuit requires 12 AWG copper conductors at minimum, based on the ampacity table for typical branch-circuit wiring methods. Using a smaller conductor than the overcurrent device requires would create an overheating hazard.

Question 50Electrical Systems

A receptacle tester indicates reversed polarity at a bedroom outlet. What condition does this describe?

  1. The grounding conductor is open
  2. The hot and neutral conductors are connected to the wrong terminals Correct answer.
  3. The circuit is protected by a GFCI
  4. The circuit is ungrounded

Explanation

Reversed polarity means the ungrounded (hot) conductor and the grounded (neutral) conductor have been swapped at the receptacle terminals. This leaves the shell of plugged-in lamps and appliances energized relative to ground.