Fixing Detached Stair Treads?

I have a staircase in which some of the treads are detached from the stringer on one side. I’ve opened the staircase from underneath and can see that one of the stringers has pulled away from the treads. I’ve attached a couple hooks, cable and a turnbuckle to pull the stringers but it only budges about 1/8-inch. The gap is between 1/8-in. to almost over 3/4-in. in some cases. Do I just replace a wider tread from underneath to fix the issue or are there any other fixes? Can I also just replace steps that are off the stringers? Do I have to replace the stringer? How difficult is this job? Do I have to hire a professional to do the job? – Martin Casino

Tim Inman: Ah for a photograph! I’m not sure if your treads (threads sic) are pulled away from the stinger horizontally (left-to-right as you face the tread) or vertically (up-and-down as you face the tread). It is possible the stringer has warped or pulled away from the treads and risers (the piece your toe would kick as you go up the steps). Using a cable system to pull the stringers back might be an option. Why did the stringer bow? If this is your problem, be careful. Staircases carry working loads. You do not want to have a tread fail while somebody is walking up and down the steps.

On the other hand, if the space you are referencing is in the “up-and-down” axis, then there might be better news. Staircases made correctly have tapered slots mortised into the stringers for the treads to lay in. Back behind the part everybody else sees (underneath the steps) there are small wooden wedges driven in to press the tread up to fit against the top of the mortise slot. This enables a tight-fitting tread, and helps stop squeaks. Sometimes these wedges work loose, or even work their way out and fall to the floor. I’m hoping this is your issue, because it would be very easy for you to correct. Just find or make new wedges, then drive them in to tighten the treads from below and behind the steps. They are not typically glued in, but rather are just a tight driven friction fit.

Chris Marshall: Martin, the first thing I’d want to determine is why the stringer pulled away at all. Is it warped or cracked? Is the floor that supports the stairwell sagging in some way, and that’s what’s disrupted the integrity of the stringer (causing it to drop and pull free of the treads? Or, maybe I’m not understanding you correctly here and the stringer has bowed away toward the ends of the treads, instead of dropping down and away? I think I’d get in touch with a licensed contractor and investigate this problem further so you can resolve any structural issues that could be safety concerns later on. And, at that point I’d probably also consider hiring him to repair the steps to make sure you are abiding by your local building codes. There’s too much at stake, including lives, if steps are built or repaired incorrectly. Be safe!

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