Stairs and Stringers for the Dummy Carpenter

stringers in stair construction

We had a lot of fun with the utter stupidity of the posts we turned up for our recent "2-by-4 Week" celebration; posts in which some idiot (we suspect a content editor or editors at Demand Media) decided that the dimensions of a 2-by-4 are in feet, giving rise to some hilarity... Some of the candidates we turned up not only weren't sufficiently on the ball to catch that stupidity while proofing, they were clearly out of their depth anyway. We're thinking of freelancers like Mary McNally and her eHow.com post, "Distance Between Stair Stringers"...

Since we already know what stair stringers are and some of our staff have built stairs, the question made sense: what's the maximum spacing suggested between stringers in a stairway? Most references say that 2-by-8 or 2-by-10 lumber treads (such as one might find on a deck) should not have an unsupported span greater than two feet (some say 18 inches), so a third stringer is advisable in wider stairways.

That's not what McNally said, however. Mary said this: "Stair stringers should be made from 2-foot by-12 foot boards. These boards should be at least 5 inches thick to provide enough support. Ninety degree angles are marked on the boards where each stair will be located. The angles are then cut with a circular saw. The tread is attached to the horizontal surface of the angle, while the risers are attached to the vertical surface of the angle." Yep, that same moronic content editor – the one who wouldn't know a 2-by-12 if s/he tripped over one – has struck again! A "2-foot by-12 foot" board, by our calculation, would weigh more than 900 pounds per running foot!

Even, however, if McNally's post had the correct dimensions – "stringers should be made from 2-by-12s" – it would be obvious that Mary had not idea what she was talking about. After all a 2-by-12 has a nominal thickness of two inches (finished thickness of 1½ inches), so where did that "at least 5 inches thick" come from?

In real life, that 5-inch dimension is the minimum allowable width of the cut stringer at any point after the notches have been cut. Instead of prattling on about risers, treads and balusters (the better to meet her minimum word count), McNally should have discussed proper spacing of the stringers and left it at that. But no, she couldn't meet her minimum word count, so instead of going into more – and perhaps more accurate – detail about stringer spacing, McNally displayed her ignorance with bogus information. What better reason for a Dumbass of the Day award?

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