I will be building a set of stairs. Stringers are exactly 16′ long. I like to try the method outline in Rick Arnold’s article (April/May 2010) and use engineered stock. The stairs are straight, not “L” shaped. Rather than use 16′ of engineered rim-board for stringers I was thinking of gluing/screwing up 12″ wide rips of 4×8 3/4″ OSB flooring rated for 24″ oc. Since I need 3 16-foot stringers I would glue/screw 2 rips of OSB (4′ – 8′ – 4′ matched up with 8′ – 8′) so there would not be a meeting of seams. This would give me 1 1/2″thick stringers. Gluing/screwing the 2×4 spacer to the stringers would essentially act as a strongback. I have extra sheets of the 3/4 OSB so I though this would be a good way to use them up. I sure would like any feedback on whether this would be an acceptable/workable alternative to 2×12’s or single engineered rimboards.
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Stairs aren't the place to skimp on materials
I am not an engineer, but as I think about what you are proposing I see some weak spots. Where you have seams, there will only be a 3/4 inch piece supporting your stairs at the 4', 8', and 12' mark. if your side stringers are being anchored directly to supporting walls, you would probably get by with this method. Probably... and you would still want something more solid for your center stringer. And how much money are you really saving IF this worked? If the 3/4 OSB is still in full sheets, you can return it. You'd need a full sheet for each stringer, so there is $15-20 per stringer in cost for the OSB. The glue would have a cost, and getting the correct glue would be very important, not to mention all the time you will spend gluing up the stringers before you could even start building your stairs. All for an end product that may not work out and will definitely be structurally inferior to the proper materials. If it were me, every time I used that staircase, I would be wondering if this would be the time it might fail! I would save the OSB and use it for your rough risers (depending on how you are building amd finishing your stairs). I would guess you ave around 18 steps, so you would use a sheet and a half just for the risers on a 4 foot wide staircase.
My philosophy is to never skimp on materials when building stairs. They are often the feature element of a house and they get lots of traffic, sometimes with heavy loads. I am a big fan of using the engineered rim boards for stringers. The are a little more expensive, but they are extremely straight, they are all the exact same depth, you don't have to worry about knots, splitting the grain with screws or nails ant you can use the entire board. If using 2x12s, i usually buy an extra 2-4 feet to make sure I don't have to use an end that has a big split in it. If the budget and headroom allow, I actually prefer to use the engineered stringers that are 1.75 inches thick and 14 inches deep, either engineered treads or 2x12s for the treads, and 3/4 OSB for the rough risers. It gives me lots of support and a very solid, stiff staircase. All treads and risers are glued/screwed in place and to each other. Is it overbuilt? Probably. But I have never regretted using better materials, especially on stairs!
osb stair stringers
second that glacierfergus
and imagine what would happen if the osb stringers get wet.
creative solutions....
Good post.
It's easy to overlook the details when improvising.
Costs of adhesives, fasteners, etc. even if labor is no concern.
Having said that i still encourage thinking outside the norm, but carefully.
It is my understanding that engineered rim boards aren't really designed to act like beams. They take a good load vertically placed on edge and supported along their length, but not really made to span across a space ... let alone 16ft. I'd consult w/ the manufacturer about it to be sure. Other pre engineered materials would work, though.
I'd think glued and screwed the OSB should work. Not much different than building a box beam or using multiple layers to create a beam. May need to do three layers, though ... two identical w/ the offset layer sandwiched between.
Code Compliant?
I'm pretty sure they site built glue ups would not be code compliant, unless you got an Engineer to say they are. And, that will cost more than you can possibly save.
It's the kind of thing I might try, but I am an Engineer, and don't have to pay for someone else to say it will work.