DIY Deck Part 2: How to Build Stairs for a Deck

Three months after my last DIY deck post, I am excited to report that our backyard deck is finally finished! If you’ve been following along on Instagram, you may have seen the final reveal video in July. This project took almost a year of both my husband and I working in the evenings and weekends. It feels surreal to have come this far and to step on the deck that we’ve built from the ground up.

In this part of the DIY deck series, I want to show you the entire process of how to build stairs for a deck. We’ve read tons of tutorials online, sifted through the information, and probably made all the mistakes there is to make with stair building, so this post is a must-read if you’re thinking of building your own deck!

In the next blog post, I will talk about how we installed railing and our choice of outdoor furniture.

Disclosure: This post contains affiliate links, meaning if you decide to make a purchase via my links, I may earn a commission at no additional cost to you.

Topics I will cover in this blog post. Click the links below to jump to the section you’re interested in:

Can you build your own stairs without much construction experience?

Absolutely! Even though we’re not professional carpenters, we made our own custom stringers for the deck with a good, solid foundation that meets standard building codes. Did we make mistakes? Yep. Did it take a while? Also yes, we spent a couple of weeks on this. Although this is the most challenging part of the entire deck build, we were able to figure out the basis and get it done ourselves with little experience. So you can certainly do the same too!

Before you start, learn these basic terms of stair construction and the international building codes. These two links are easy to read and you should be able to breeze through it in no time.

Installing a paver landing pad

Step one, let’s figure out the total rise. Total rise is the total height of the stairs from the top of the deck to where the stairs are going to land on the ground. The standard height of a stair riser is 7 inches (don’t exceed 7 3/4 inches). Knowing how high the deck is above ground and how high each step is, we can easily calculate the number of steps the stairs will need.

Since our backyard slopes down due to grading, we needed to finish the landing spot first.

Digging rock-hard clay soil by hand with shovels was no joke. We brought our kids along, but they quickly got bored and went and played with dirt in the yard. We also got sored pretty easily, and had to chip away at the soil over the span of two days. If you have an auger or can rent a mini excavator, the job would be a lot easier.

We leveled the ground, tamped the soil, laid landscape fabric, added a thin layer of paver base, then three rows of 12×12 concrete pavers on top of black paver panels. The panels served as a base for the pavers and were a total game changer. They allowed us to dig only a few inches below ground, saving us from back pain, sore arms, and a boatload of sand. It was our first time using them. And we liked how easy they were to install.

To keep everything in place and looking polished, we also added paver edging and marble rocks .

Why use pavers instead of concrete for the landing?

The short answer is we were lazy. LOL. Prepping the ground, building the slab frame, mixing and pouring concrete seemed like a lot of work. Given my past experience DIYing with concrete, I wasn’t confident I could do it properly to prevent cracking in the future.

Most of our neighbors used pavers, so we knew pavers met code and would be easier to deal with.

If you want to look into building concrete landing, this tutorial by Bourbon Moth Woodworking is a good one.

You can also check out Room for Tuesday’s How to Install A Custom Paver Patio

All the math for the stair stringers

Once we finished building the landing, it was time for measuring. We balanced a long 2×10 on top of the deck, keeping it level, while measuring the vertical distance from right underneath the lumber to the landing spot. This picture shows how my husband did it with the assistance of our little helpers.

Our stair height turned out to be 40 inches.

Since we wanted each step to be the standard 7 inches height, we divided 40 inches by 7 inches to get to 5.7 steps. We rounded it down to 5 steps, because we wanted the first tread to be one step down from the deck surface (non-flush stringer) vs. having it lined up with the top of the deck (flush stringer).

This image explains the difference between the two designs. Source: https://chieftalk.chiefarchitect.com/

Now comes the 1st equation: number of steps = total rise / 7 inches, round up for flush stringer, round down for non-flush stringer.

Next, we needed to determine the total run of the stairs. The run of a stair is the horizontal dimension of a staircase. It’s the part of the stairs that a person steps on, also known as the tread. Standard run depth is 10 inches minimum.

2nd equation: total run = number of steps x 10 inches

With 5 steps, 10 inches each step, our total run was 50 inches. Easy peasy.

How to calculate the tread and riser for each step

The next steps in the calculation were a bit more complex. We handed off the work to our phone. There are many construction calculators online, such as this one. After comparing the output available, we liked the iOS app “Feet and Inches Calculator” the most.

You can find it in app store, and enter the measurements mentioned above.

Plug in the total run (X axis), total rise (Y axis) and tread thickness (thickness of the deck board), we got the cut diagram for our stringers. The calculator also checks if the measurements meet common building standards (see these green checks on the top). Pretty handy, right?

How to mark and cut stringers

I have to admit when I first saw all the notations on the output screen, my eyes kind of glazed over. After reading the diagram a couple of times, it started to make sense. Don’t be discouraged if you also feel a bit lost when you get your result. Just keep at it.

Then we could mark the cuts. Mark the A points (red dots) according to the distance shown on the diagram, then draw the purple lines (W and H lines) using a framing square. Repeat for each of the stair steps (triangles in teal color on the diagram).

You can see in the first picture below how we clamped down an aluminum framing square with quick-grip clamps, lined it up with the A points, to mark the outline of the stringers. You can also use this trick to make a jig to speed things up.

The stringer cut diagram provided by the app helped us visualize where the cuts were and compare with the pencil marks we made on the 2×12 board. This way, we could double check if the measurements were correct.

To make the cuts, we used scrape wood as a guide and cut along the lines with a circular saw.

Tip: make sure to account for saw blade width (kerf) and cut on the outside of the lines, so that you don’t accidently cut away more wood than is necessary.

Because the circular saw can’t cut through the underside of the stringer when the top of the saw blade reaches the end point (see picture below, the blade is round), we finished off the cut with a jig saw.

Then we held our breath and set up the stringer next to the deck.

And it fit! The stringer sat perfectly on the pavers and against the deck rim joist.

And the air bubble right in the middle. Woohoo! This meant the steps were level.

These cuts were not the easiest to figure out. We felt so extremely proud of ourselves for pulling this off.

How many stringers do you need for deck stairs?

It depends on the materials you’re using for the treads.

Wood stairs require a maximum of 16” spacing between stringers. Composite decking, on the other hand, needs less spacing or more stringers. The manufacturing guide for Deckorator’s deck board says the maximum on center spacing is 8″, which meant we needed to have 7 stringers in total for 48″ wide stairs.

I know, it’s a lot. But with the first stringer done, we could use it as a template and work our way through the task. Time to put on some music, rinse and repeat.

It took a couple of days to finish all the cuts. We felt a sense of accomplishment to see all 7 stringers neatly lined up next to the deck. The day to actually walk up to the deck is not far away. We’d been acting like ninjas to get on and off the deck the last few weeks.

How do you attach stringers to the deck?

Start by adding a stair header if you’re doing non-flush stringers.

Let me explain why it’s necessary.

If you fasten stringers to the rim joist without a stair header, the hangers will be dangling in the air (see the picture below?) and there isn’t enough support to handle the heavy load of people walking up and down the stairs. A stair header extends the rim joist of a deck and providers a solid surface for the metal brackets to attach to. So your stairs will last longer.

There are different ways to make a stair header. This demo on the Trex Academy tutorial is a great one.

You can also do something similar to what we did: glue two 2x12s together and secure them to two trimmed down boards, to make a L shape structure.

Securing stair headers and notching stringers

We screwed in the support boards from behind the rim joist, and used a right angle attachment for drilling, because the space under the deck was super tight. Don’t forget to get a cushion for your back, if you need to lay down on the ground for installation. This was a very uncomfortable position.

After a lot grunting (you rock, hubs), it was finally done.

To make sure the stringers will be installed at the right distance from each other, we also planned out where each of the stringers will go and marked the locations on the rim joist.

At this point, we were so ready to install the stringers. But wait, the stringers were floating freely on the pavers. We needed some kind of mechanism to prevent the stringers from moving from side to side.

We notched the stringers at the bottom and place them on top of a 2×12 that’s the same width of the stairs.

Tip: before installing stringers, mark the outline of a stringer on a fascia board. Doing so makes sure the angle and length of the covering will match the stringers.

Securing stringers to rim joist

After all of the revisions, we eventually nailed in these babies with a palm nailer and 12″ clamps. It was a smooth process and only took a few hours.

Look at that! Stair stringers in.

This is what the framing looked like. We added a 2×12 base under the notched stringers, several blockings between the stringers, and toe nailed the stringers to the blockings, blockings to the 2×12 base. We also added larger blockings to support the stair posts, similar to how we did it on the deck.

Tip: measure the distance between stringers on the top of the stairs and at the bottom before securing everything. You want the stringers to be perfectly square and evenly spaced.

Don’t forget to add these large blockings on the corner to support the railing posts.

How to install deck steps

Finally came the part to make the stairs look pretty.

Start by cutting the deck boards to length. The riser boards need to be ripped down, while the tread boards can be installed as is, as long as they meet the overhang requirement (read tip below). Because the joist hanger next to the house exterior prevented us from screwing in a separate piece of fascia, we had to remove the first board we put up there and cut a new one that covered the long strip on the side.

Tip: leave an overhang of ¾” to 1 ¼” for the stair treads.

For each step, we installed the riser boards first, then the tread boards.

Make sure to check manufacturer instructions and use the right fastener before installation. Since fascia/risers are thinner than deck boards, you may need to use screws only vs. a plug system.

If you make a mistake and need to remove the deck boards, you can drill into the plug with a coarse thread screw and pull the plug right out. As shown in this video.

DIY staircase in all its glory

After all the hurdles and that steep learning curve, getting the staircase done (minus the tricky fascia) felt amazing. We couldn’t stop running up and down it, like it was the coolest game ever.

In contrast to what the same spot looked like before, we’re a lot closer to the finish line. See the before and after video on how to build stairs for a deck here.