You have a vision of what your deck should be when it’s finished. You can already smell the barbecue from the grill and are ready to spend time on your new deck with friends and family. You’ve spent time planning it out, and now it’s time to actually assemble it—and that includes building the stairs. A deck stairway adds visual interest, utility, and should be built with safety in mind, but if you’ve never built stairs before, it can be a little tricky. Building stairs requires exact measurements and careful layout. Here is some information that should help you out on your first stair building experience.
Stair Terminology—Understand It FIRST!
Before you can build some stairs of your own, you need to understand the deck-builder’s lingo.
The most common style of deck stairs is a straight run of notched stringers. A stringer is the structure of the stairs. They are often notched pieces of lumber that support the treads. They must be strong enough to support the heavy loads imposed by people walking on the steps themselves. This is usually 2×10” or 2×12” minimum.
Each step consists of the tread which are the horizontal pieces a person steps on when going up or down the stairs. The riser is the back part of the step. It’s the height between the treads; the vertical part. Nosing is the overhang of the tread.
Step 1: Figure Out the Rise & Run
This will be a throw back to your algebra classes in high school. There’s a formula that deck builders use for the ideal relationship between the rise and run. Yep—you’re going to have to do a little math in order to build your steps!
- Twice the rise plus the run should be between 24-26”.
- 7½” + 7½” Rise + 10” Tread = 25”.
- The sum of one riser and one tread should equal 17-18”.
- The riser multiplied by the tread should equal between 70-75”.
It’s extremely important that all of the treads and all risers be at the same size and height, so measure carefully and don’t just “think” that it’s “about” this height or that height. Your trusty tape measure is your best friend when you’re building your stairs. Why? Because after your stairs are built and someone walks up or down your stairs, they will subconsciously measure the height of the first few risers. If your stairs aren’t the same height, you will have people tripping up or down your stairs because they are not the same height. Todd’s number one rule of building stairs is measure twice!
Step 2: Determine the Number of Risers
The total vertical distance a stair must cover is measured from the top of the decking to where the stairs will land. If the ground slopes away, make sure you measure where the stairs will land.
Divide the distance in inches by 8” of rise. In the event that the number is not even, round up to the nearest whole number. Then divide the original distance by that number to find the height of each riser.
Here is an example to illustrate this process: 75” ÷ 10 = 7½” per riser. If you want a lower rise, divide by 11 and get 6 13/16” per riser.
I like to cut the tread at 10”. This works out nicely for decking as two 5 ½” decking boards = 11” + 1/8” gap = 11 1/8” so you will have an overhang of 1 1/8”.
And here is another little helpful hint from Todd. There is always 1 less tread than riser, so if you have 10 risers you will have 9 treads. Nine treads x 10” each; the stairs would land out at 90”.
Step 3: Cut the Stringers
Place a 2×10” or 2×12” of appropriate length on a pair of sawhorses. You need to sight along the edge of the lumber to determine if there is a crown.
As you are cutting, make sure the crown side is up. Figure 3-1. Using a framing square, set the buttons to 7½” and 10”. Start on the bottom of the stringer and continue along the length, marking off each step. After marking the notches, I make several critical adjustments before cutting the stringers. Shorten the bottom step to the thickness of the tread material.
Mark 1½” off the bottom front riser, and mark 1½” off the back of top riser.
Figure 3-2. Using a circular saw, cut out the steps–running the front of the blade just to the intersection of the marks for riser and treads. Because the blade is circular, there will be a bit if wood remaining on the underside of the stringer. Cut this with a hand saw or Jigsaw. After your first stringer is created, use this one for a pattern for the remaining stringers.
Step 4: Assemble the Stairs
Figure 4-1. Attach and screw a 2×6” on the top back of stringers and 2×6” on the bottom front stringers for support.
Temporarily tack the stair section to the deck. Now locate where your bottom rail posts will be installed. Remove stairs and dig holes to code depth.
Reattach stairs, square stringers, plumb, and securely attach the posts to the front 2×6” and outside stringer.
Figure 4-2. You are now ready to install the riser and tread material to your stringers. I like to start at the bottom and work my way up. Install the riser material first and follow by securing the treads. Screw the bottom back of each riser to the tread. I like to add another 2×4” along the side of each stringer for double the strength.
Add skirt boards on the side of each outside stringer for a more finished look.
After building decks for almost 25 years, I’ve “learned by doing.” Some common things that people make mistakes on are that they do not realize that the variation between the largest and smallest riser can be no more than 3/8” and that the maximum riser height is 8”. Open risers on stairs are not permitted. Nor do people realize that the minimum stair width is 36” and that they need a railing on stairs if there are over 3 risers. There also is a minimum tread depth of 9”.
I think that my “top 4” list of things that you need to be aware of when building your first set of stairs are: Don’t put your top tread even with your deck. Remember when adding railing on both insides of a set of stairs, you shrink them by around 1”. Some stair kits require between 30 and 35 degree angles for the stringers. Lastly, some companies recommend strings be at 12”, so be sure to read their recommendations.
It’s good practice to always consult with your local building department. All city codes are not the same and you want to build a deck that fits within your city’s code. It’s also good to know that every city does not have to adapt to the National building code.
Todd’s Final Thoughts
Every time I build a deck, it’s a different experience. The things I’ve shared in this article are just helpful hints about how I’ve learned to build stairs for decks over my career. Every deck has its own challenges, and building the stairs to a deck is what completes the deck. Take your time to plan well, do the math, measure twice, cut once, and adjust to your conditions. If you do those things, your stairs will be sturdy and strong, just like your deck!
Todd Funfar is the owner and operator of DeckMasters in Fargo, ND. He can be reached at 701.232.4001 or www.deckmasters.net.
Terminology
Stringer – The structure of the stairs;
notched pieces of lumber to support treads;
it must be strong enough to support heavy loads imposed by people walking on the treads;
usually 2×10” or 2×12” minimum
Riser – Is the back part of the step. The height between the treads; the vertical part
Total Rise – The sum of all the risers divided by ?
Tread – Each step consists of a tread which is the horizontal pieces you step on
Total Run – The sum of all the tread is the total run
Nosing – Overhang of tread
Skirt boards – Finish board to cover treated stringers, ends of decking, risers and a more finished look.
