BuiltByMAC

Hey all,

I've been chewing on this subject for a while. I'd like to start a discussion on the various ways to build a strong set of stairs. Primarily, I'd like to find new ways of building stairs that don't require an intermediate support . Whenever I get a set of stairs taller (longer) than 10 risers, my staircase feels bouncy and weak in the middle. I end up installing an intermediate post/beam to stiffen the structure.


The 2x6 X bracing on the flat gives lateral stability but doesn't do much to stiffen the staircase for vertical loads.

I've built one staircase that had no intermediate supports and is strong as hell. I used 6 2x12x20s - 4 for the cut stringers and 2 for strongbacks glued and screwed to the outside stringers.


The HO wanted a deeper set of stairs than 2 deck boards so I made it with 7" risers and 13 1/2" tread cuts. With that much meat cut out of the 2x12, I knew I had to beef up the staircase. I glued and screwed the solid 2x12s on either side, holding them below the cut line so the treads/risers could extend out. I built 2x6 X bracing below the stringers to help support the inside stringers.



That's the closest I've come to a bombproof staircase. It's rock freakin' solid...but it also took a great deal of time and materials to create.

I've never tried mortising treads/risers into a closed stringer. All my stringers have been pressure treated wood so I want to hide it - under treads/risers, behind fascia boards, etc.

I'd be interested in hearing from you guys as to some of your best practices for strong stairs. A lot of you are great builders, I've seen your pics. School's in session, I'm ready to learn!

Thanks,

Mac

framerman

Only thing I could think of is pressure treated glu-lams.

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Cole

Mac, that is a great looking set of stairs.

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BreyerConstruct

Mac,

I'm usually studying you, so I don't have too much to add.
Something we've done is step up to more stringers. We usually use 4 2x12's per 4' set of steps. The extra 2x12 seems to help.

Here's a thought, as we're trying to hide the PT, what if you put a 2x6 down the inside of the outside stringers- right up tight to the treads?
Does that make sense?

~Matt

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RobertCDF

The 2 most bombproof stairs I ever built were these:

1. most recent 5' wide 9 treads? maybe 8... stringers at 8" O.C. solid as a rock

2. 4' wide steps stringers at 12" O.C. the 2 outside stringers were not cut at all. I had 2x6 blocks bolted to the sides on layout with the cut stringers. Did this 2 times and I think they were 16-17 treads. Very solid.

Hide anything you want with fascia and or paint.

My advice would be microlam stringers for the strongest solution... Very expensive solution but a solution.

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neolitic

I do same as you, 4 stringers with uncut strongback/skirt boards. On long runs that "must" be unsupported sometimes we run a 2X6 between the outside stringers and the skirt board (maybe just a carryover from interior work). And another trick is not notching the stringer so deep. I learned by watching, only easy way I've ever been able to teach is--tack a 2X2 to the top of your "pattern", lay it out, pull the 2X2 and cut 'er. This only works if you're gonna put in risers (riser supports nose of tread cause of missing "point" on stringer nose). Make any sense? Have done same with "open" interior stairs. Just 2 stringers and notch the back side of 2X12 treads between stringers--solid as hell 20 years later.
Hope some of that made sense, not too sure I can understand me sometimes

neolitic

Just saw where you are--I'm jealous of all that doug fir youse guys get out there. These days we need a requisition signed by God to get that stuff back here

y0manda

If my stringers have more than 6 risers I use glu-lams period! 2x12's suck and they suck even worse after a year.

BuiltByMAC

If I'm understanding you correctly, that would put the 2x12 strongback 1 1/2" away from the cut stringer, plus you'd still need a ripped 1x4 on the flat to cover the top of the pt.


Alright, now I have to try that! I always use risers that are at least 3/4" thick (cedar or composite 1x) so that might be enough support for the leading tread board. I'll try this out on a shorty stair case I'm building tomorrow (5' wide by 4 risers high) to see how it comes together. It won't give me feedback on the strength issue but it will let me mess around with the idea without burning up too much time and materials. Hmmm, on the job training? I'll post some pics when I'm done.

Try again, please. I'm not understanding the "notch the back side of 2x12 treads" part...

Thanks

Some stuff better than others but I've not seen your selection. I do remember seeing pt in Vegas when I was down there for a working vacation and realizing how good the stuff back home was (ummm, I was talking about the wood!)

Uh, huh... Glad to see you brought your positive attitude into this thread too.

--------------------------------

Mac

Bone Saw

for starters, narrowest stairs I'd build would be 4' with 4 stringers (stringers never exceeding 16"oc) this alone will substantially stiffen it.. regularly I build 14, 15 16 rise stairs on 9" basments (terrain dependant) and I've never put any of the bracing or such in place, occasionally if I have to "tighten the rise up" subsequently lowering the pitch I'll put in intermediate support to the outer stringers, much the way you'd scribe and cut gable wall studs to the end rafter, very clean streamlined install, does the trick. but most importantly I try to make the stairs as "monolithic/unibody" as possible, 2x glued and nailed for risers mitered riser joints at outer stringers, and full length t/b (cap where applicabl) rail lapping as opposed to in between posts, this acts to form a "truss" with the outer stringers, very stiff and strong, I try to keep , I see you do the bottom 's of your stairs same as me with a "sill" I shoot mine into my "pie caps" with ramset of titans, I think you'll find puttingg your railpost outside as opposed to inset will aid in the rail truss effect, in a nutshell 2x risers, keep em light (stain instead of comp facia) and "unibody" railing. will greatly stiffen it, obviously lower pitches will need more reinforcement than steeper pitches, I hate the liik of risers, more so from the ground than from beingon them or on the deck, I'm trying to go to a 2 stringer, riserless mortise and tennon sTAIR WITH intermediate support where needed for a super sleek look, im drunk, good night

reveivl

Way to go Bonesaw!!

Mac, what happened to the pics?

All I really have to say on this is that it is a span issue. Your stringers are spanning a distance (given) and have a strength (optional) and an o/c measurement between them (optional). So you have three options: decrease the span, increase the strength, or decrease the o/c measurement. That's it. No mystery, no secrets.

I also think that the half-lapped 2x6 cross bracing you have underneath those really nice stairs you built, is doing almost nothing. If you really want, and need, cross bracing to work, you get the most bang for the buck at 45 degrees, but with treads and risers all attached appropriately, I don't think that sway bracing is doing much. It ain't hurtin' tho', and it looks real purty.

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BuiltByMAC

Were they not showing up last night? When I responded to this thread around 10 pm last night, they were there. They're there this morning as well. Maybe my web server was doing maintenance when you were looking at this thread

Which stairs are you talking about? The grey TREX deck or the one with black railings? Both sets have the 2x6 cross bracing at approx. 45º, the grey TREX railing deck has the 2x6's vertical as opposed to the black railing one where the 2x6s are on the flat against the back of the stringers.

Both really stiffened up the staircase against lateral sway, however, the 2x6s on the flat did nothing for increasing the strength.

Bonesaw, you made some really good points. I'll try some things out on my current project and post pics of the progress.

Edit to add: I'm limited by code to a 4" opening in my stairs - the only way a riserless system would work would be to have under a 5 1/2" rise or use 4x material for the treads. I made a staircase 3 years ago with 4x10 uncut stringers and 4x10 treads on metal stair brackets - talk about a heavy freakin' staircase!

Excellent discussion, guys! This is how we learn...

Mac

Chris G

Surfboards come to mind. They're built with stringers that run along their length for stiffness.

Lots of info on the stiffness of different wood species here. Also, they repeatedly refer to wood stiffening over time.

http://www.waveequation.com/wood_stringer_data.html

At the risk of going against the grain of code adherence, it may better to toss out the pressure wood on some occasions.

Has anyone used steel plates attached to stringers?

John Hyatt

All I can add is 2x6 blocking inbetween the 16'' on center stairbucks installed between the risers with construstion adhesive. Also I have found with my projects placing the rail posts inside/blocking them in makes for a stronger rail system and helps stiffen things up.

I use that 490 adhesive on everything including the finish treads/skirting and riser faseing. I go with all the metal conectors I see on your project Mac with a simular brace underneith for any stairway over 8' long.

Thanks again for the pictures!!! John

BreyerConstruct

I'm not the best explaining with the keyboard... let me re-phrase it.
If your rail posts are on the outside of your stringers, you could scab a 2x6 on the inside of those outside stringers, just lifting it "up" until it hits the treads... This would give you that stiffness, without too much bracing & difficult work.

Oh, if the rail posts are on the inside, you could 2x the inside stringers- both sides even.

Does this make sense?

PS. the idea about cutting the notch out shallower works well, but not for all decking. if it's ribbed, and not a full board (Think Trex Contours instead of Trex Accents) then you could have some issues with it sitting flat.

FWIW I almost always build my steps with a 7" rise, which works out on a Trex deck to be just enough room between 2x6 treads for a 5/4 board to be wedged in, which helps tighten everything up.

~Matt

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BuiltByMAC

'Smacks head while saying "doh", ala Homer' - I get it now!

Thanks for re-explaining it -

Mac

Bone Saw

just to add to the "unibody" comparison, take a set of premade stairs for carpeting, usually just 1x pine outer stringers with everything mortised glued and stapled together, yet relatively very strong. fasteners, glue and most importantly TIGHT JOINERY to make a monolithic structure as opposed to a series of members bearing down on other members and so on and so on. try mitering gluing and nailing your outer stringer rise cuts to your risers like this, very strong

EasTnBldr

I've really enjoyed the pics and read of this thread. Generally I add more stringers or apply a 2x4 or 2x6 nailer to each side of the stringer (depending on cut depth) to help with "spring" in my step. I did take note of the original comment about 7" risers with a 13" plus tread depth ... my stairs would fail inspection here. They hold us pretty stringent to the (double your rise and add your tread) 24" - 25" min/max allowed. If I'm not mistaken, it's national code but I know that the inspectors in MI were more interested in max. riser height and min. tread depth than anything else.

Again ... thanks for the thought provoking responses. We've had a stair way fail in the area recently. Of course, it was a rental cabin in the Smokies and 20 plus people staying at a cabin thought it a "great photo op" to all stand on them simultaneously. Sadly, the stairway failed killing a couple people and sending all but 2 to the hospital for care.

John Hyatt

BoneSaw thats a good idea!! just cut the riser back 1 1/2'' and run a solid 2x6 ghessssss thats one of those why dident I think of that things. We usually cut the shorts laying around for the blocking but man that would go so much faster I can use those shorts someplace else.

Also runing all those fasteners thru the 2x12 always has a risk of split out/repair a risk greatly lessened byfase fastening Its always the little things.

Thanks Man! John

mickeyco

Great thread (and nice work on those decks), the one thing I've noticed is that I have never seen a stringer that has failed, even over-cut ones, it has always been the attachment at the top. For a strong set of stairs I like a good attachment at the top and bottom (if possible), I think an attachment at the bottom goes a long way towards making the stairs feel a lot sturdier and can take some of the load off the top connection. I also think blocking or cross bracing the bottom does a lot to reduce any deflection of the stringers. I repaired a stair case on an old house (had to remain the same in appearance) and cut an extra set stringers (3) and used 6" x 1/4" x (length of stringer) steel plate (not that expensive) sandwiched and bolted between the two stringer like a flitch beam, I covered the steel with that plastic like lintel flashing and bull-nose routed small channels in the stringers for drainage, I'd bet you could drive a car up those stairs. Several of the jurisdictions out this way will make you use an intermediate brace above a certain height (varies in different jurisdictions) unless you have an engineers stamp. Sometimes I'll add a 2 x 6's the way BreyerConstruct said:

Here's a pic:

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