National Home Inspector Exam (NHIE) · Home Inspection (All Domains)
National Home Inspector Exam (NHIE): Structure and Foundation Concepts
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Overview
This chapter covers the parts that hold the house up: footings, foundation walls, posts, beams, joists, and the crawlspace or basement around them. The inspector looks for signs that the structure has moved or is being damaged by water, and explains how serious those signs appear to be.
Cracks tell a story by their shape. Thin vertical cracks in poured concrete are often from normal shrinkage. Stair-step cracks in block or brick suggest settling, and horizontal cracks in a block wall can mean soil pressure is pushing the wall inward. Wide cracks, cracks that are offset, or walls that lean deserve a referral to a structural engineer.
Framing members can be weakened by careless cuts. Under common model codes, notches and holes in joists are limited in size and location. Moisture is the other big threat: look for efflorescence on masonry, water stains, wood rot, and poor crawlspace ventilation.
Key concepts
Footing
The wide base under a foundation wall or post that spreads the house's weight over the soil. In cold areas the bottom of the footing must sit below the local frost depth so freezing soil does not lift it.
Memory tipNo footing, or a post sitting on bare dirt, is a structural concern.
Crack patterns
Thin vertical cracks in poured concrete are often shrinkage. Stair-step cracks in masonry suggest settlement. Horizontal cracks in block walls often mean soil is pushing the wall in. Wide, offset, or growing cracks need an engineer.
Memory tipHorizontal crack plus inward bow in a block wall = refer to an engineer.
Joist notches and holes
Under common model codes, notches in sawn lumber joists are typically limited to one-sixth of the depth and are not allowed in the middle third of the span. Bored holes are limited to one-third of the depth and kept at least 2 inches from the top and bottom edges.
Memory tipNotches at the ends are allowed if small; notches mid-span are not.
Source: International Residential Code (ICC) · as of 2021
Efflorescence
White, powdery salt deposits left on concrete or masonry when water moves through the wall and evaporates. It is not harmful by itself but shows that moisture is getting through.
Memory tipWhite powder on basement walls means water has been there.
Crawlspace ventilation
Under common model codes, a vented crawlspace typically needs at least 1 square foot of vent opening for each 150 square feet of floor area. With a ground vapor retarder this can drop to 1 per 1,500. Sealed crawlspaces are another allowed design.
Memory tipRemember 1 in 150, or 1 in 1,500 with a vapor retarder.
Source: International Residential Code (ICC) · as of 2021
Often tested
- Describe crack type, size, and location rather than guessing the cause.
- Refer wide, offset, or horizontal cracks to a structural engineer.
- Check posts for solid bearing and secure connections to beams.
- Water stains, rot, and standing water in crawlspaces are common findings.
Easy to confuse: Reading foundation cracks
| Crack type | Common cause | Usual response |
|---|---|---|
| Thin vertical (poured concrete) | Normal shrinkage | Note and monitor |
| Stair-step (block or brick) | Settlement | Describe; refer if wide or offset |
| Horizontal (block wall) | Soil pressure pushing in | Refer to a structural engineer |
3 sample questions
Verified practice questions from this unit.
Question 1. A hairline vertical crack in a poured concrete foundation wall, with no offset and no water, is most often caused by:
- ① Shrinkage as the concrete cured
- ② Major foundation failure
- ③ A leaking roof
- ④ Termites eating the concrete
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Answer: ① Shrinkage as the concrete cured
Key point: Hairline vertical cracks are usually concrete shrinkage
Concrete shrinks as it cures, so hairline vertical cracks are very common in poured walls. If there is no offset (one side shifted), no widening, and no water, it is usually not structural. Inspectors still report it and may suggest sealing and monitoring.
Wrong choices
- Major foundation failure: A hairline crack with no offset or movement is not a sign of major failure.
- Termites eating the concrete: Termites do not eat concrete.
- A leaking roof: Roof leaks do not crack foundation walls.
Question 2. A horizontal crack along the middle of a concrete block basement wall, with the wall bowing inward, is commonly caused by:
- ① A leaking roof
- ② Soil pressure pushing on the wall from outside
- ③ Normal concrete shrinkage
- ④ Too much attic ventilation
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Answer: ② Soil pressure pushing on the wall from outside
Key point: Horizontal cracks with bowing = soil pressure
Soil outside a basement wall pushes inward, more so when it is wet or frozen. Block walls are weak against this sideways pressure, so they crack along a mortar joint near mid-height and bow inward. This is a serious structural concern.
Wrong choices
- Normal concrete shrinkage: Shrinkage cracks are usually vertical and do not cause bowing.
- Too much attic ventilation: Attic ventilation has no effect on the foundation.
- A leaking roof: A roof leak does not push a basement wall inward.
Question 3. A stair-step crack following the mortar joints in a block or brick wall usually indicates:
- ① Mortar that was just applied
- ② A lightning strike
- ③ Settlement where one part of the foundation moved more than another
- ④ Normal shrinkage of new mortar
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Answer: ③ Settlement where one part of the foundation moved more than another
Key point: Stair-step cracks point to differential settlement
Masonry cracks along the weakest path, which is the mortar joints. When one part of a foundation settles more than another (differential settlement), the crack steps up or down diagonally. Width and offset help show how serious it is.
Wrong choices
- Normal shrinkage of new mortar: Shrinkage cracks are fine and scattered, not a clear stair-step pattern.
- Mortar that was just applied: Fresh mortar does not form stair-step cracks.
- A lightning strike: Lightning is not the usual cause of stair-step cracks.