The Corner That Moves: Foundation Crack, Notched Joist, and a Post on a Slab
A 1962 split-level with a poured concrete foundation is being inspected for a buyer. In the finished basement, a 1/8-inch-wide diagonal crack runs from the top of the front-left corner of the wall down to the slab, and it is widest at the top. Above it, on the floor above, a hairline crack runs diagonally from the corner of a window head. The basement slab slopes about 1 inch in 12 feet toward that same corner. Nearby, a 2x8 floor joist spanning 12 feet has a 3-inch-deep notch cut at midspan to clear a 2-inch drain pipe. A steel post supporting the main beam bears on the 4-inch slab with no visible footing, and the slab has a radial crack around the post base.
1. Read the crack pattern and decide what you will report and recommend.
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Read the pattern, not just the crack.
- Curing/shrinkage cracks are typically uniform in width along their length, run vertically or in a random map pattern, and are not echoed by movement elsewhere.
- This crack tapers - widest at the top - is diagonal, and is matched by a crack above the window head one floor up. The 1-inch-in-12-feet slab slope toward the same corner is a fourth symptom pointing at one location.
Report: location, width (1/8 inch), length, orientation, the interior crack, and the slab slope, all as observations, plus the date and the moisture conditions at the exterior corner if you can see it.
Do not: name a cause or state that the foundation is "settling," and do not state that the structure is sound. Write that the cause was not determined and recommend a licensed structural engineer evaluate that corner, the footing, and site drainage there.
Why: the cause could be soil, drainage, a footing, or a combination, and it may still be active. Your job is to see it and hand it to the right professional, not to diagnose it.
2. Evaluate the notched joist and decide how to word the finding.
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The limits: for solid-sawn joists, notches are allowed only in the top or bottom edge, no deeper than one-quarter of the joist depth, and never in the middle third of the span.
- A 2x8 is 7 1/4 inches deep, so the maximum notch is about 1 13/16 inch.
- This notch is 3 inches deep and sits at midspan - the worst possible location, where bending moment peaks.
Consequence: net depth drops to roughly 4 1/4 inches, about 60 percent of the original section, which cuts bending capacity and stiffness sharply. Expect squeaks, deflection, and eventual ceiling cracks; the pipe can also be loaded by the joist as it deflects.
Report: state the measured notch, its location relative to the span, and what it was cut for; call it a structural framing alteration; state plainly that you did not evaluate the adequacy of the framing; recommend a licensed structural engineer or a contractor's repair design (sistering, a header, or rerouting the drain). Do not write "probably fine."
3. The post bears on a bare 4-inch slab with a radial crack. What is your judgement and what do you recommend?
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What the evidence supports: a post needs to bear on something designed to spread its load and to hold it in place. Here you have a point load landing on an unreinforced-looking slab with no visible footing, no post base or anchor, and a radial crack fanning from the contact point - a classic pattern for a slab being punched or flexed by a concentrated load. You cannot see below the slab, so you cannot rule out a proper footing beneath it.
Report: the post, the absence of a visible footing, base, or anchor, the radial crack, and the beam it supports, described as observed. Note that the slab is not a verified structural bearing element.
Recommend: a licensed structural engineer evaluate the post/beam/footing arrangement. Do not tell the buyer to "just add a base plate" - that is a design decision, and a plate may not solve a slab that isn't adequate. Do point out that the post is the load path for the floor above, which is why it matters.