A lot more goes into building safe deck stairs than a lot of people realize. Sure, deck stairs often aren’t all that long. Maybe a couple of feet at most, but every now and again you’ll have a set of deck stairs that make you wonder whether or not they could use a little extra support.
As a general rule of thumb, stair stringers – the part that the actual stairs sit on – do not require extra support until you get stringers longer than 10 feet. Once you hit that magic 10 foot mark, though, it’s a good idea to build in at least a little bit of extra bracing.
Let’s go over when and why deck stair stringers might need a little bit of extra support right now.
Do Deck Stair Stringers Need Support?
The overwhelming majority of deck stairs are going to have stringers that are under 6 feet in length.
Because these stringers are built with heavy duty materials (likely pressure-treated 2 x 12s) and do not have all that long a span you don’t have to tuck any extra support more bracing in underneath them.
These are not the kinds of deck stairs that are going to start sagging anytime soon!
Of course, there are some deck stairs that can use a little bit of beefing up. Here are three core factors that help you decide whether or not you’ll want to call in a little bit of cavalry to help carry the load.
Three Factors Determine Support
Length
As soon as you start to get closer to 10 feet in length – and certainly once you hit anything over 10 feet for your stringers – you’ll want to start thinking about beefing things up a little bit.
These kinds of runs MAY do all right without any extra bracing. But you’re still talking about a long stretch that a single piece of lumber has to carry on its own. Over time these things are going to start to sag without bracing in the middle.
Material Choice
The kind of construction material you are working with is going to have a huge impact on whether or not you beef up and brace these deck stair runs as well.
2 x 12 (or thicker) pressure-treated construction material isn’t going to have a lot of give to it when you get out to 10 feet or so. Beyond that it can get a little bit wiggly, but anything under 10 feet is going to be just fine fully unsupported.
Jump up to a 2 x 14 or a 2 x 16 of pressure-treated material and you’ll be able to get another foot or two of unsupported length. You’ll have to pony up a premium for these kinds of boards, though, and it may not be cost-effective.
Untreated material, composite material, or even metal steps may have different spans that they can handle without any extra support. You need to consider the material being used before you decide on bracing.
Bounciness
Lastly, you just want to think about how bouncy your steps are right now as well as how bouncy they may be in the future.
If your deck steps are built like a rock and have absolutely zero give, you probably don’t need to add any extra support at this point.
If, come of years down the line, though things start to get a little wiggly you might want to add at least a bit of bracing. You give yourself a lot more peace of mind knowing that things are shored up.
Sags on your stairs are always a sign that extra support is needed – or that major repairs (and possibly even complete replacements) need to be undertaken.
What Kind of Support?
You have a couple of different options to add extra support to deck stairs that need it.
The easiest (and often the most cost-effective) approach for adding extra bracing is simply to sister up another stringer – at least to the middle stringer – to give yourself a little more stability.
Sure, that can be a little bit annoying to have to cut for stringers for a set of stairs instead of three. But the extra stability you get with this approach is going to pay off big time. Particularly as you get closer to that 10 foot trigger we mentioned a moment ago.
On really long stair runs some folks even go with full on braces position to about halfway down the stair run. You usually only see these on decks that are quite a bit elevated off the ground, though. We are talking 12 foot stair runs or even longer than that.
Where Deck Stairs Break Down
If you’ve begun to notice that your stairs are little bouncy and a little wiggly you want to be sure that it’s the stringers themselves that are no longer able to carry the load and not another component tricking you into that conclusion.
Sometimes stairs feel squishy simply because the tread or riser material has started to break down a little bit. Every time you step on a board that’s coming apart it feels like the entire set of stairs is about to pitch over when nothing could be further from the truth.
The way that stringers are attached to the deck (as well as to the footing) can also be a major contributor into how weekly or wobbly otherwise solid stairs feel.
If the stringers haven’t been attached correctly, or if the wrong fasteners have been used, you are probably going to be dealing with a relatively quick and easy fix.
Be sure that you check to see how the stairs are attached to the footer as well.
A lot of folks feel that setting a flight of stairs down on top of a footer is “good enough”, not realizing that while these stairs have full bearing the fact that they can float is inevitably going to cause detachment from the top of the stairs.
Lockdown both the top and bottom of your stairs and you won’t have anything to worry about in that department!
Closing Thoughts
Do deck stair stringers really need support?
Most of the time (when we are talking about deck stairs that are 3 feet to 6 feet long) you can get away without having to beef up your stairs.
When you hit that 10 foot stair stringer length, though, you want to start thinking about how you can better support the run for sure.