Stairs are one of the trickiest parts of any deck build, and I have cut my share of stringers, good and bad, over the years.
Quick answer: Deck stairs are made of stringers, treads, and risers that carry people safely from your deck down to the ground. The basic rule of stair building is simple math. You measure your total rise, divide it into even steps, and every single step needs to match that same height.
What Are Deck Stairs?
Deck stairs are the steps that connect your deck down to the ground. They have a few main parts working together.
The stringer is the sawtooth-shaped board that holds up each step. The tread is the flat part you actually step on. The riser is the vertical piece that closes off the front of each step, though some stair designs skip this piece on purpose. The landing pad is the solid base at the bottom where the stairs meet the ground.
I’ve found that stairs get more attention from inspectors and more complaints from homeowners than almost any other part of the deck. That is because uneven steps are dangerous. People walk stairs without looking down, and their feet expect every step to feel the same. This guide focuses on getting that consistency right.
Stairs are just one piece of the whole project, so make sure to read our complete Deck Building guide to see how this step fits into the full process from footings to railings.
The Simple Math of Stair Building: Rise and Run
Stair math sounds scary, but it is really simple once you break it down.
Total rise is the full vertical distance from the top of your deck surface down to the ground. You measure this straight up and down, not along a slope.
Total run is the full horizontal distance the stairs will cover from the top step to the bottom of the last step.
Here is how you turn total rise into individual steps. Say your total rise is 63 inches. Most codes call for a step height, called the riser height, somewhere around 7 to 7.75 inches. Divide 63 by 7, and you get 9 steps. Then divide 63 by 9, and you get exactly 7 inches per step. Every single step needs to come out to that same 7-inch height, no exceptions.
The tread depth is the horizontal part of a step where your foot lands. Most codes want somewhere around 10 to 11 inches of tread depth for a comfortable, safe step.
Standard Stair Dimensions
| Measurement | Typical Range | Notes |
|---|---|---|
| Riser height | 7 to 7.75 inches | Every step must match exactly |
| Tread depth | 10 to 11 inches | Comfortable and code-friendly range |
| Stair width | 36 inches minimum | Check local code for your exact minimum |
| Total rise tolerance | Very small variance allowed | Uneven steps are a common trip hazard |
Always check your local building rules before cutting your wood, since exact numbers can vary a bit by area.
Choosing and Spacing Your Stair Stringers
A stringer is the sawtooth-shaped backbone of your stairs. It gets cut from a solid board, usually pressure-treated 2×12 lumber, and the notches cut into it form the shape of each step.
You need heavy-duty lumber here because stringers carry foot traffic directly, with no other support layer helping them out. A 2×12 gives you enough material to cut deep notches for the steps while still leaving a strong solid section behind each cut.
Stringer spacing matters just as much as joist spacing. Standard wood treads usually work fine with stringers spaced around 16 inches apart. Composite treads often need tighter spacing, usually around 12 inches, because composite material can flex more than solid wood between supports. From my experience, skipping this detail with composite treads leads to a bouncy, springy feeling on every step.
Stringer Selection Guide
| Stringer Material | Typical Spacing | Notes |
|---|---|---|
| Pressure-treated 2×12 | 16 inches | Standard for most wood tread stairs |
| Pressure-treated 2×12 (composite treads) | 12 inches | Tighter spacing prevents flex |
| Wide stairs (4+ feet) | Add a center stringer | Extra support for wider steps |
How to Use a Framing Square and Stair Gauges
A framing square is a large steel L-shaped tool, and stair gauges are small clamps that attach to it. Together, they help you mark the exact same cut line over and over, which is the secret to getting every step identical.
Here is how it works. Clamp one stair gauge at your riser height measurement on one arm of the square, and clamp the other gauge at your tread depth measurement on the other arm.
Now every time you lay the square against your board, the gauges line up in the same spot, and you trace the same angle every single time.
This matters because even a small difference between steps, something like a quarter inch, is enough to trip someone who is not expecting it. One mistake beginners make with stairs is eyeballing each step separately instead of locking in their gauges and repeating the exact same layout every time.
Stair Layout & Math Verification Checklist
[ ] Measure total rise from deck surface straight down to the ground
[ ] Confirm total rise measurement in more than one spot
[ ] Divide total rise into equal steps within code range
[ ] Confirm every calculated riser height matches exactly
[ ] Confirm tread depth falls within a comfortable code range
[ ] Set stair gauges on the framing square before marking any cuts
[ ] Double-check the first stringer layout before cutting
The Ground Landing Pad: A Solid Base for Your Steps
You cannot just set your stringers down on open dirt or grass. Bare ground shifts with rain, frost, and time, and your stairs will slowly sink, tilt, or settle unevenly if they land on soft earth.
A concrete landing pad gives your stairs a solid, flat, stable base to rest on. Pour a simple flat concrete pad sized to fit the width of your stairs, or use solid heavy pavers set on a properly prepared gravel base as a lighter alternative.
I’ve found that skipping this step is a shortcut that always shows up later, usually within the first year or two, as the bottom of the stairs starts to feel uneven compared to the top.
Deck Building 101: The Complete Guide
Deck Railings: A Complete Guide
Step-by-Step Guide to Cutting and Installing Deck Stairs
A “deck stair parts” diagram labeling the stringer, tread, riser, and landing pad would help readers see how everything fits together.
Step 1: Measuring Total Rise and Calculating Step Dimensions
Measure your total rise carefully, then run your math to find the number of steps and the exact riser height and tread depth for your layout.
Step 2: Laying Out the First Stringer with a Framing Square
Set your stair gauges, then trace each step notch onto your first stringer board using the same gauge settings for every single mark.
Step 3: Making the Cuts Carefully with a Circular Saw and Hand Saw
Cut along your marked lines with a circular saw, then finish the inside corner of each notch with a hand saw, since a circular saw blade cannot fully complete an inside corner cut without overcutting.
How to Cut Plywood Sheets with Circular Saw: A Guide
Stair Cutting & Safety Checklist
[ ] Wear safety glasses during all cuts
[ ] Wear gloves when handling pressure-treated boards
[ ] Support the board fully before cutting to avoid binding
[ ] Finish inside corners with a hand saw, not an overcut circular saw pass
[ ] Check the first stringer against your layout before cutting more
[ ] Keep the work area clear of scrap cutoffs while cutting
Step 4: Using the First Stringer as a Template to Trace the Remaining Supports
Once your first stringer looks right, use it as a template to trace and cut the rest, keeping every stringer perfectly identical.
Step 5: Fastening Stringers to the Deck Frame Using Code-Approved Metal Stair Hangers
Attach the top of each stringer to the deck frame using approved metal stair connectors, never just a few angled screws. That top connection point ties directly into your deck’s rim joist, so check our complete Deck Framing guide to make sure that rim joist is properly reinforced to carry the extra load from the stairs.
Step 6: Securing the Bottom Ends to the Concrete Landing Pad
Anchor the bottom of each stringer to your landing pad using proper connectors rated for ground-level contact, keeping the wood from sitting directly in standing water.
Step 7: Fastening the Stair Treads and Risers Securely
Install your tread boards and riser boards using structural connector screws, checking that each step sits flat and level before moving to the next.
Common Stair Errors Beginners Make
Forgetting to subtract the tread thickness from the bottom stringer cut. This small measurement mistake makes the very first or last step taller or shorter than all the others.
Using weak screws that snap under foot traffic. Stair treads take a lot of repeated impact, so always use proper structural connector screws rated for this kind of load.
Creating an uneven bottom step. If your landing pad height was not accounted for correctly in your rise calculation, the last step ends up a different height than the rest, which is a serious trip hazard.
Skipping the metal stair hangers at the top connection. Toe-nailing the stringers to the rim joist alone is a weak connection for something people will be stepping on and putting weight on every day.
Frequently Asked Questions
What is the difference between open risers and closed risers? Open risers leave a gap between each step with no vertical board, while closed risers have a solid board closing off the front of each step; check your local code, since some areas limit how large an open gap can be.
Can I add lighting to my deck stairs? Yes, many builders add small step lights or riser lights, usually low-voltage, for visibility at night.
What do I do if my total rise doesn’t divide evenly? You adjust your riser height slightly within the acceptable code range until the math divides evenly across your total rise.
Do all deck stairs need a handrail? Many areas require a handrail once you have more than a few steps, so check our complete Deck Railings guide for the safety details and code-friendly spacing rules.
How wide should deck stairs be? Most codes call for a minimum width around 36 inches, though wider stairs are common for a more comfortable feel.
Can I use standard deck screws for stair treads? It is better to use structural connector screws rated for repeated foot traffic, rather than standard general-purpose deck screws.
Do I need a center stringer on wide stairs? Yes, stairs wider than about 4 feet typically need an added center stringer for extra support under foot traffic.
How do I handle a stair layout on a sloped yard? You may need a taller or shorter final step, or an adjusted landing pad height, to account for the slope where the stairs meet the ground.
Can stringers sit directly on dirt instead of a landing pad? This is not a good long-term solution, since bare dirt shifts with rain and frost, causing the stairs to settle unevenly over time.
Why does my bottom step feel different in height from the rest? This usually means the landing pad thickness or tread thickness was not factored into the original rise math correctly.
Final Thoughts
Deck stairs come down to careful math and consistent cuts. Take your time measuring total rise, lock in your stair gauges, and use your first stringer as a perfect template for the rest.
If you want to see how stairs fit into the whole build, check out our complete Deck Building guide. Got a question about your own stair layout? Drop a comment below. I read every one.
