21 Structure & Foundation Practice Questions & Answers

1. 1. An inspector is explaining to a client why a residential foundation wall is built on a footing that is wider than the wall itself. What is the footing's primary structural function?

   • A.To form a waterproof barrier that keeps groundwater out of the basement
   • B.To spread the load from the wall over a larger area of soil so that the bearing pressure stays within what the soil can carry✓ Answer
   • C.To resist the inward lateral pressure that backfill soil exerts against the wall
   • D.To act as a capillary break that stops moisture from rising into the wall

   A footing works by distributing a concentrated wall load across enough soil area that the resulting bearing pressure remains below the soil's allowable bearing capacity, which is why footings must sit on undisturbed native soil or engineered fill rather than on loose backfill or organic topsoil. Waterproofing, resisting lateral soil pressure, and capillary breaks are performed by other components of the assembly.

   Source: National Home Inspector Examination content outline — structural systems: foundations and footingsReport a problem with this question

2. 2. In a basement with concrete block foundation walls, an inspector observes a continuous horizontal crack along a mortar joint near mid-height of one wall, with the courses above the crack displaced inward relative to the courses below. What does this pattern most strongly indicate?

   • A.Frost heave lifting the footing beneath that wall
   • B.Lateral pressure from the backfill soil, frequently made worse by water saturating the soil behind the wall✓ Answer
   • C.Downward settlement of the footing beneath that wall
   • D.Normal shrinkage of the mortar as the wall cured

   A block wall loaded horizontally by soil bends like a vertically spanning beam, so it cracks along a bed joint near mid-height and bows inward — the classic signature of lateral soil and hydrostatic pressure. Settlement and heave move the wall vertically and produce vertical, diagonal or stair-step cracking instead; the inspector reports the observed condition, notes it as a significant concern, and recommends evaluation by a structural engineer rather than diagnosing the exact cause.

   Source: National Home Inspector Examination content outline — structural systems: foundation defects and applied forcesReport a problem with this question

3. 3. An inspector finds stair-step cracking through the mortar joints at one exterior corner of a masonry foundation, wider at the top than at the bottom, together with an out-of-square door frame and a floor that slopes toward that same corner. This pattern most strongly suggests which condition?

   • A.Lateral soil pressure pushing the wall inward
   • B.Curing shrinkage of the mortar, which is purely cosmetic
   • C.Differential settlement — that corner of the foundation has moved downward relative to the rest of the structure✓ Answer
   • D.Seasonal truss uplift transmitted down through the framing

   Stair-step cracking follows the weakest path through mortar joints when one part of a masonry wall drops relative to another, and a crack that widens toward the top indicates rotation about a lower point, so the corner has settled; the out-of-square door and sloping floor are corroborating interior evidence of the same movement. Lateral pressure produces a horizontal crack with inward bowing, and truss uplift shows as a seasonal gap at the ceiling-wall junction, not foundation cracking.

   Source: National Home Inspector Examination content outline — structural systems: foundation movement and crack patternsReport a problem with this question

4. 4. A poured concrete basement wall in a house less than a year old shows several fine vertical cracks of nearly uniform width, with no offset between the two faces of the crack, no displacement of the wall, and no staining or dampness. What is the most likely explanation?

   • A.Corrosion of reinforcing steel embedded in the wall
   • B.Shrinkage as the concrete cured; the inspector should still describe the cracks and recommend monitoring✓ Answer
   • C.Hydrostatic pressure acting against the wall
   • D.Settlement of the footing under that wall

   Concrete shrinks as it cures and releases that stress as fine cracks of fairly even width with no displacement, typically appearing within the first year and generally not indicating structural movement. Movement cracks differ in that they taper, offset, or displace one side relative to the other, and rebar corrosion announces itself with rust staining and spalling of the concrete cover.

   Source: National Home Inspector Examination content outline — structural systems: concrete foundation defectsReport a problem with this question

5. 5. A house sits on expansive clay soil. Interior drywall cracks at the corners of door openings widen during a long dry period and partially close again after a wet season. Which mechanism best explains this behavior?

   • A.Continued curing shrinkage of the concrete foundation over many years
   • B.The clay shrinks as it dries and swells as it takes on water, cyclically lowering and raising portions of the foundation✓ Answer
   • C.Thermal expansion and contraction of the framing lumber
   • D.Water in the soil freezes and expands beneath the footings each dry season

   Expansive clay changes volume with moisture content, so portions of a foundation resting on it rise in wet periods and drop in dry ones, and that seasonal shrink-swell cycle shows up indoors as cracks that open and close with the weather. Frost action requires freezing temperatures rather than dry weather, and neither lumber thermal movement nor concrete curing shrinkage reverses itself seasonally in this way.

   Source: Residential foundation engineering fundamentals — expansive soils and shrink-swell movementReport a problem with this question

6. 6. In a cold climate, an inspector finds a pier-and-beam house whose masonry piers were set in shallow holes only a short distance below the ground surface. Which mechanism most threatens this foundation?

   • A.Frost heave — water in the soil freezes and expands, lifting the piers, which then settle unevenly when the soil thaws✓ Answer
   • B.Shrink-swell of expansive clay caused by the weight of the piers themselves
   • C.Hydrostatic pressure collapsing the piers inward
   • D.Capillary rise carrying moisture upward into the wood beams

   Water expands as it freezes, so in frost-susceptible soil the freezing zone lifts anything bearing within it and the support drops unevenly on thaw, producing cyclic movement, cracked masonry and uneven floors. That is precisely why bearing surfaces are placed below the local frost depth, where the soil beneath them does not freeze.

   Source: Residential foundation engineering fundamentals — frost action and depth of bearingReport a problem with this question

7. 7. An inspector observes a white, crystalline, powdery deposit on the interior face of a masonry basement wall; the wall is dry to the touch at the time of inspection. What is the most accurate interpretation?

   • A.Mold is growing on the wall and remediation should be recommended
   • B.Water has moved through the masonry and evaporated, leaving mineral salts behind — evidence of moisture movement rather than structural damage in itself✓ Answer
   • C.The deposit is freeze-thaw spalling of the masonry surface
   • D.The wall has lost structural capacity and requires immediate engineering evaluation

   Efflorescence is the mineral salt left behind when water migrates through masonry and evaporates at the surface, so it documents that water has been moving through the wall even if the wall is dry today. It is not decay, not mold, and not structural damage; the inspector reports it and looks for the water source, most often exterior grading or roof drainage.

   Source: Residential building science — moisture movement in masonry and efflorescenceReport a problem with this question

8. 8. A below-grade wall encloses finished living space at a site known to have a high water table. Which statement correctly distinguishes the two common below-grade wall treatments?

   • A.Dampproofing is simply a heavier application of the same material used for waterproofing, so either one is suitable here
   • B.Both treatments are intended only to control water vapor, and neither resists liquid water
   • C.Dampproofing resists dampness and water vapor where no hydrostatic pressure exists, while waterproofing is a membrane-type treatment meant to resist liquid water under hydrostatic pressure — the latter is what a high water table calls for✓ Answer
   • D.Waterproofing is applied to the interior face of the wall and dampproofing to the exterior face

   The two treatments are defined by the load they resist: dampproofing is a coating that stops capillary and vapor moisture where water is not standing against the wall, while waterproofing is a continuous membrane system designed to hold back liquid water pushing on the wall. A high water table or other severe soil-water condition therefore calls for the membrane-type treatment plus functioning perimeter drainage.

   Source: Residential building science — below-grade dampproofing versus waterproofingReport a problem with this question

9. 9. A basement shows staining and efflorescence along the wall-to-floor cove joint on one side of the house only. Outside that same wall, a downspout discharges directly at the foundation and the grade slopes back toward the house. What should the inspector recommend first?

   • A.Correct the roof drainage discharge and the negative grade first, because surface water is the most common source of a wet basement and the least invasive thing to fix✓ Answer
   • B.Install an interior perimeter drain and a sump pump
   • C.Underpin the foundation on that side of the house
   • D.Apply a sealer paint to the interior face of the basement wall

   The overwhelming majority of wet basements are surface-water problems rather than groundwater problems, and the localized evidence here lines up exactly with the downspout and reverse slope on that one wall. Managing roof runoff and re-establishing fall away from the foundation is the first, least invasive corrective step; interior drainage, sealers or underpinning address symptoms or unrelated conditions and are premature.

   Source: National Home Inspector Examination content outline — site grading, drainage and below-grade moistureReport a problem with this question

10. 10. During a remodel, a heavy point load from an upper floor was brought down onto a post that bears on the finished floor above ordinary floor joists, with no beam, column or footing beneath it in the basement below. What is the principal structural concern?

    • A.The load path is interrupted — a concentrated load must be carried continuously through framing, posts and footings down to the soil, and here it stops at joists that were not designed to receive it✓ Answer
    • B.The only issue is that the post will restrict future use of the basement space
    • C.The point load will push the foundation walls outward at the top
    • D.Nothing is wrong, because the floor joists will distribute the load evenly to the foundation walls

    Every load in a building must follow a continuous path — roof to rafters or trusses, to bearing walls and headers, to joists, to girders and columns, to foundation walls and footings, and finally to the soil — and each link must be present and connected. A post landing mid-span on joists breaks that chain and overloads members in bending, and the inspector reports the interrupted load path and recommends evaluation rather than judging how much load the joists can take.

    Source: National Home Inspector Examination content outline — structural systems: load path and vertical supportReport a problem with this question

11. 11. In a house with conventionally framed rafters and a ridge board, the ties that spanned across the lower portion of the rafter span were removed during an attic conversion. The inspector now finds the exterior walls leaning outward at the top and the ridge line sagging. Why did this happen?

    • A.The ridge board lost its ability to carry the vertical load of the roof
    • B.Those lower ties resisted the outward thrust that rafters exert at their bearing points; without them the rafter feet spread the walls and the ridge drops✓ Answer
    • C.Those were collar ties whose only function was to resist wind uplift at the ridge
    • D.Removing them reduced dead load, which allowed the roof to rebound upward

    Rafters bearing on a ridge board behave as a triangle whose base must be held: rafter ties in the lower third of the span take the horizontal thrust in tension, and cutting them lets the rafters rotate outward, spreading the walls and dropping the ridge. Collar ties are a different member, located in the upper third near the ridge, and they resist uplift and ridge separation rather than thrust.

    Source: National Home Inspector Examination content outline — structural systems: roof and ceiling framingReport a problem with this question

12. 12. What distinguishes a structural ridge beam from a ridge board in conventional roof framing?

    • A.A ridge beam is used only on hip roofs and a ridge board only on gable roofs
    • B.A ridge beam carries roof load and must be supported by posts continuing down a load path to bearing, which eliminates outward thrust at the walls; a ridge board is essentially a nailing surface and the assembly depends on ties to resist thrust✓ Answer
    • C.The two terms describe the same member and are used interchangeably
    • D.A ridge board carries the roof load while a ridge beam merely aligns the tops of the rafters

    A ridge board does not carry vertical load; it only aligns and provides a nailing surface for opposing rafters, so the rafter pair acts as a triangle and needs ties at the bottom to resist outward thrust. A structural ridge beam does carry load and transfers it through posts to a continuous load path, so the rafters bear on it rather than pushing the walls apart, and mislabeling one for the other leads to missing the need for ties.

    Source: National Home Inspector Examination content outline — structural systems: roof and ceiling framingReport a problem with this question

13. 13. An inspector finds that a web member of an engineered roof truss has been cut through so that a duct could pass. What is the appropriate response?

    • A.Calculate the truss's remaining capacity and state in the report whether it is still adequate
    • B.Report it as a significant structural defect and recommend that a repair be designed by a qualified engineer or the truss manufacturer's designer✓ Answer
    • C.Recommend sistering the cut web with a piece of dimensional lumber of the same size
    • D.Note it as a minor workmanship item, since web members carry little load

    A truss is an engineered system in which every chord and web carries a specific tension or compression force, so cutting any member redistributes forces the assembly was never designed for and can lead to progressive failure. The inspector's role is to describe the condition and refer it to the truss designer or an engineer; specifying a field repair or computing remaining capacity would be engineering work outside the scope of a visual home inspection.

    Source: Home inspection standards of practice — reporting defects and recommending further evaluationReport a problem with this question

14. 14. A homeowner reports that a horizontal gap opens between the ceiling and the interior partition walls each winter and closes again in summer. The roof is framed with engineered trusses. What is the most likely explanation?

    • A.Truss uplift — seasonal moisture differences between the top and bottom chords arch the bottom chord upward; it is a serviceability and cosmetic issue rather than a structural failure✓ Answer
    • B.The foundation settles each winter and rebounds each summer
    • C.The bottom chord of the truss has failed in tension
    • D.Snow load has permanently deflected the roof structure

    When the top chord sits in cold, damp attic air while the bottom chord stays warm and dry above the insulation, the differing moisture content makes the bottom chord bow upward, lifting the ceiling off non-bearing partitions until conditions reverse. The pattern is seasonal and reversible, which distinguishes it from settlement or a failed member, and it is reported as a cosmetic and serviceability condition.

    Source: Residential roof framing behavior — seasonal truss upliftReport a problem with this question

15. 15. Two identical floor joists of the same span have each had material removed at mid-span: one has a notch cut into its bottom edge, the other has a round hole bored near mid-depth. Why is the notch the greater structural concern?

    • A.Round holes never reduce a joist's capacity, regardless of their size or location
    • B.Bending puts the bottom fibers at mid-span in maximum tension, so cutting there removes the most highly stressed material and creates a stress concentration at the notch corner, while material near the neutral axis contributes least to bending resistance✓ Answer
    • C.The bottom of a joist is in compression, and wood is weakest in compression
    • D.Notches matter only because they expose end grain and encourage decay

    In a simply supported bending member the extreme fibers are the most stressed — bottom in tension and top in compression at mid-span — and stress falls to nearly zero at the neutral axis in the middle of the depth. Removing tension-zone material at mid-span therefore costs far more capacity than a hole placed near the neutral axis, and the sharp inside corner of a notch adds a crack-initiating stress concentration; this principle, not a memorized fraction, is what tells an inspector which cut to flag.

    Source: Structural mechanics of bending members — principles behind notching and boring limitsReport a problem with this question

16. 16. In a basement, an inspector finds an adjustable steel screw post supporting a built-up wood girder. The post is not fastened at the top or the bottom, it bears directly on the basement floor slab with no separate footing pad, and its base is corroded where the slab is damp. What should the inspector do?

    • A.Report only the corrosion, since an unfastened post is normal for adjustable columns
    • B.Determine the size of footing pad that is required and specify it in the report
    • C.Consider the arrangement acceptable, because the floor slab distributes the load to the soil
    • D.Describe these conditions as defects affecting the support and lateral stability of the girder and recommend evaluation and correction by a qualified contractor or engineer✓ Answer

    A column is part of the load path only if it is positively connected at the top and base and bears on a footing sized for the load; a floor slab is not a footing, an unconnected post can shift or be displaced laterally, and base corrosion signals persistent slab moisture that will continue. The inspector describes the observed deficiencies and refers them out, because determining the required footing or the adequacy of the support is beyond a visual inspection.

    Source: National Home Inspector Examination content outline — structural systems: columns, beams and connectionsReport a problem with this question

17. 17. A floor feels noticeably springy underfoot, but the visible joists and girder show no sagging, cracking, decay, or loss of bearing. What is the best way for the inspector to handle this?

    • A.State in the report that the joists are undersized and specify sistering as the required repair
    • B.Leave the observation out of the report, since a springy floor is not a failure
    • C.Calculate the joist span and publish the allowable load for the floor in the report
    • D.Describe the observed bounce as a stiffness and serviceability concern, recommend further evaluation, and note that a visual inspection does not determine the adequacy of framing sizes or spans✓ Answer

    Excessive deflection is a stiffness and serviceability problem that can exist while the members are still strong enough not to fail, so it is a real, reportable observation even without visible damage. Standards of practice describe a home inspection as visual and not technically exhaustive and exclude determining the adequacy of structural systems, spans and member sizes, so the correct report language states the condition and refers it out rather than sizing a repair.

    Source: Home inspection standards of practice — scope, limitations and exclusionsReport a problem with this question

18. 18. In a hot, humid climate an inspector finds a vented crawl space with condensation and surface mold on cool duct surfaces and on the underside of the floor during summer, while the same crawl space is dry in winter. What is the most likely mechanism?

    • A.A plumbing supply line is leaking on a seasonal cycle
    • B.The crawl space simply has too few vents, and adding more openings will resolve the problem
    • C.Warm, humid outdoor air entering the vents condenses on surfaces that are colder than its dew point, so ventilation can add moisture in this climate rather than remove it✓ Answer
    • D.Groundwater seeps through the foundation walls only during the summer months

    Air can hold less water vapor as it cools, so humid summer air drawn into a crawl space that is chilled by the ground and by cold ducts reaches its dew point and deposits liquid water on those surfaces, feeding mold. This is why in humid climates a vented crawl space can be a moisture source and adding vents typically makes it worse; the corrective direction is ground moisture control and a sealed, conditioned or dehumidified crawl space.

    Source: Residential building science — crawl space ventilation and condensationReport a problem with this question

19. 19. In a crawl space, an inspector finds scrap lumber and buried form boards lying on the soil, a girder end only a few inches above exposed earth, and a ground vapor retarder that is torn and pushed aside. No insects, tubes or fungal growth are visible. How should these findings be handled?

    • A.Report them as evidence of an active infestation and state that chemical treatment is required
    • B.Report only the torn vapor retarder, treating the debris as a housekeeping matter
    • C.Report them as conditions conducive to wood-destroying organisms and decay, because together they supply the moisture, cellulose and earth contact those organisms require✓ Answer
    • D.Omit them from the report, since no organisms or damage were actually observed

    Reporting "conditions conducive" is exactly what a home inspector does: cellulose debris on the ground, earth-to-wood proximity and an interrupted ground vapor retarder together create the damp, food-rich, soil-connected environment that decay fungi and wood-destroying insects need, whether or not organisms are present today. Declaring an active infestation or prescribing treatment goes beyond the visual scope and belongs to a qualified pest specialist.

    Source: National Home Inspector Examination content outline — conditions conducive to wood-destroying organismsReport a problem with this question

20. 20. Which statement about fungal decay in structural wood is correct?

    • A."Dry rot" is decay that occurs in genuinely dry wood, so controlling moisture cannot stop it
    • B.Surface mold and mildew on framing are the first stage of structural decay and directly reduce the strength of the wood
    • C.Decay fungi require wood that stays wet — roughly above twenty percent moisture content — so "dry rot" is a misnomer, and drying the wood and removing the moisture source arrests further decay✓ Answer
    • D.Decay fungi need only warmth and oxygen; the moisture content of the wood is unrelated to whether decay progresses

    Decay fungi need four things at once — cellulose to eat, oxygen, a favorable temperature, and free water in the wood — and removing any one of them stops the process, which is why moisture control is the practical cure. The term "dry rot" describes wood that decayed while wet and later dried, not decay of dry wood; surface mold, by contrast, is a staining and indoor-air issue that does not consume the wood's structure.

    Source: Wood durability fundamentals — decay fungi and wood moisture contentReport a problem with this question

21. 21. In a crawl space an inspector finds galleries excavated in a sill plate that are smooth and clean, free of soil, with coarse sawdust-like debris on the ground below and no earthen tubes anywhere on the foundation. Compared with subterranean termite damage, this pattern is best characterized how?

    • A.Not reportable at all, because insect evidence lies entirely outside the scope of a home inspection
    • B.Identical to subterranean termite damage, which also leaves clean, soil-free galleries and no tubes
    • C.Proof of powderpost beetles, which leave large open galleries and never produce exit holes
    • D.More consistent with carpenter ants, which excavate galleries for nesting rather than eating the wood; the inspector reports the visible evidence and the conducive conditions and recommends evaluation by a qualified pest specialist✓ Answer

    Subterranean termites keep contact with soil and pack their galleries with soil and fecal material, leaving layered, soil-flecked damage and shelter tubes over foundations and piers, while carpenter ants only nest in wood softened by moisture and leave galleries that look smooth and swept, with coarse frass pushed out below. A general home inspection is not a wood-destroying-organism inspection, so the inspector reports what is visible and the conditions conducive to it and defers identification and treatment to a qualified pest professional.

    Source: Wood-destroying organism evidence — damage characteristics and inspector referralReport a problem with this question

Practice questions based on the National Home Inspector Examination content outline, widely shared home inspection standards of practice, and residential building science. Not affiliated with or endorsed by any examination board, licensing authority, or inspector association. A home inspection is a visual, non-invasive examination and is not a code-compliance inspection — nothing here should be read as a code requirement. Home inspection is regulated differently from place to place; confirm your own jurisdiction's requirements and the standards of practice you are held to before testing or inspecting. About the National Home Inspector Examination →