I’m afraid I don’t agree. @Caribbean_cruiser says it goes all the way through where it’s wide enough to measure and I think it’s optimistic to assume that it doesn’t go all the way through in the parts that are too tight to fit a feeler gauge. I also agree with @moes_lotion that the basement stringer looks awfully thin.
Where is this crack along the run of stairs? Near the top or bottom or in the middle?
IF I’M CORRECT HERE (and I’m assuming I’ll get corrected here if I’m not), this is all cosmetic, so you’d be just fine removing the paint, using wood filler and re-painting.
The stringer is the part BELOW the tread - you know, the part holding the stairs up. This is just the molding.
If it’s the same design as the other exposed stair, the treads are routed into the stringer, which is exposed, so the whole thing is structural (especially if it is thinner than standard 2x stock).
It may continue cracking after gluing and patching. That would require replacing the bad part of the stringer. It’s a big job that requires a good carpenter. Hopefully that isn’t needed.
Carpenters will usually build outdoor steps or something small. Just a few steps. Stair cases with spindle railings are more specialized. There are companies that will take measurements and have a stair case custom made.
I agree that the crack isn’t cosmetic or minor, but IMHO, nor is it in danger of rapidly expanding – providing it isn’t stressed by a parade of circus fat men. The worst cracking is located next to the fourth and fifth step on the six-step staircase (which itself is located above a landing area.)
My immediate plan of action is (a) to clean out the crack by blowing and very lightly scraping or chiseling out the old wood, without significantly enlarging the crack (b) use a tiny palette knife and syringe to inject in as much epoxy as possible, filling it from the farthest/deepest part of the stringer outward, allowing the first, deepest application to dry first and (c) mark with a pencil the farthest edges of the crack, so I can determine whether it is continuing to lengthen. I will hold off on cosmetically covering the area with primer/paint, just so I can monitor it. If I later feel the need to open up the drywall, I will open it to the SIDE of the stringer, so I can screw in a series of mending plates, so that these plates are later hidden behind drywall, and also brace the staircase with additional lumber. (If I have to open the drywall, I will go big with every corrective fix I can think of.) That said, even with the side of the staircase exposed, it will not be easy to reach the crack, I believe.
I appreciate the wisdom, gentlemen.
Being that it’s only a 6 step staircase, I’m less worried–there’s only so much load you can inflict in that short a run. Plus, you’d be amazed at the inertia of buildings–they actually do want to stay standing (right up till they don’t, of course). Sounds like you have a good plan.
Anatomy of a staircase.
Wide view of staircase.
A lot of work, but these would help make a secure joint if used before you injected glue:
Looking at the backside photo I don’t think you have standard construction for a stair case. Instead of common stringers you have some composite construction where the sides are made of 1x wood with triangular tread ledges glued to them, with those wedges aligning the steps and risers. It may have been a kit, but maybe just something homebrewed.
I don’t recall you mentioning the width of the treads. I’m guessing if they’re 30 inches wide or less that construction is strong enough. I don’t think you should go overboard mending that crack. Trying to hold it together with pocket screws, zip bolts, or the like might further crack the ‘stringer’. I think you should try to get some epoxy in there to stop it from getting worse. Otherwise you might as well add some reinforcement across the crack for a real hold.
Good luck!
You’d mentioned earlier needing to work fast with epoxy. Just so you know, epoxies come in a huge range of formulations and some of them have very long working times (an hour or more). Some also come in less viscous formulations that might be easier to inject into the crack.
The stairs are 36 inches wide, and they feel very solid. Some creaking but that’s on several steps both above and below the landing. I will go with the epoxy approach and see how that works, while measuring the ends of the crack to see if it’s migrating. My history with “going the extra mile” on DIY projects and basically doing a super-textbook job is that I’m punished for it as often as rewarded, and the punishment really stings.
I didn’t know that. Very helpful!
That’s the reasonable attitude. Trying to fix something to be better than new is a folly. We’re lucky when repairs reach the point of ‘as good as new’.
Another easy option is to attach a 2x4 from the back of the stringer to the floor. Acting as a post that transfers the weight.
It may not be ideal because it blocks that area under the stairs.
The pic of the underside of the stairs is from a different staircase in the same house that’s (probably) of the same construction as the problem staircase.
The OP has repeatedly said that there is zero underside access to the problem staircase.
Late to the party, but I do have a few comments.
The thickness of the stringer is completely normal looking to me. Its just made from 2” dimensional lumber - which is 1 1/2”. A stringer that uses actual 2" material is going to be custom, likely stain grade, open riser, etc. Your standard builders grade staircase is just going to be dimensional lumber or plywood. A 1 1/2" thick stringer made from 2x10 stock is totally normal.
If the crack isn’t growing, creaking, etc it is stable and nothing to worry about. Fill it with a flexible filler, bondo is probably best, sand and paint.
Regular PVA wood glue and epoxy are not going to do much. PVA needs to have generous contact with both surfaces and be mechanically compressed. You would need to thoroughly inject it and clamp or drill pilot holes and screw it. Epoxy is too viscous and not going to penetrate. Some really thin polyurethane or specialty furniture grade cyanoacrylate may work.
If it was really compromised and I truly wanted to fix it, I would expose it from the other side (yes, remove drywall and framing) and sister lvl, plywood or perhaps rim board to the entire length. But more likely at that stage, just replace that stair run The local stair shop would make a new run for a few hundred.
Thank you, gents. Much to mull. I honestly wasn’t expecting much response to my enquiry, believing SDMB wouldn’t have much DIY expertise.
One of the posters mentioned using a thinner epoxy. All the epoxies I’m aware of are all thick and need to be sort of troweled into place. I did read epoxy glue can be thinned using a solvent. however. My goal would be to inject the epoxy using a syringe. I doubt JB Weld epoxy can be injected that way.
If you want to use JB weld, get a putty knife and work it into the crack that way. Probably end up working better than trying to inject it.
One epoxy supplier is https://www.westsystem.com/
They manufacture a range of epoxies for marine use and are generally more expensive that your garden variety hardware store brands.
I’m not sure what their smallest sizes are, but have kept their System 105 resin and hardener stored in a fridge for a few years with no appreciable loss of quality. Just don’t mix up the caps when you reseal the bottles.