Clear for Landing

Mark’s new house is comfortable, compact, and beautifully finished… but his builders made a couple of mistakes. First, the basement stairs weren’t built to code. A support column squeezes the basement stair landing too close to the top of the stairs, forcing risers about 8 ½ inches high when code limits them to 7 ½ inches. Second, the landing for the upper stairs is sagging due to inadequate support.


Part of the landing support for the upper stairs pokes out over the basement stairs.

The obvious solution to the first issue is to move the support column – it needs to slide about 15 inches to make room for the basement stairs. So, let’s think like an engineer: what are the consequences of moving the column? One consequence is that the column no longer supports the end of the collector beam; it leaves a cantilever. An unintentional cantilever is never good, but 15 inches isn’t that big of a deal when the beam itself is 12 inches deep. We agreed to lag a stringer to a nearby LVL, reducing the load on the cantilever.

Another consequence is that the column no longer stands on a concrete footing but is supported by the slab directly. I went through a checklist to see if I was OK with that move. Slab construction? On grade. Soil underneath? Extremely dense glacial till, no risk of consolidation. Loads above? Just the first floor itself; the exterior walls are the only loadbearing walls in Mark’s whole house. I concluded the slab might be more susceptible to cracking, but structurally it could support the moved column just fine.


The offending support column is in the foreground just right of the insulation. It needs to move 15 inches to the right.

The second issue took a little more investigation. The exposed bit of landing support provided a big clue, and so did a nearby first floor joist that deviated from the pattern. My diagnosis was this: the upper stairs were built too narrow at first, and when they were widened an extra piece of landing was tacked on, resulting in another of those pesky cantilevers. I recommended Mark rebuild the landing as a single frame. He could do the job while the basement stairs were out, supporting the upper stairs temporarily from the basement floor.


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