Calculate Stair Dimensions and Stringer Type

What happens in this clip

Once the total height is established, determine whether your stair stringers will be 'inside mounted' (attached between joists) or 'outside mounted' (attached to the outside face of the rim joist). Next, use a specialized online stair calculator, such as the one mentioned at decks.com, to input the total height and your chosen run dimension (e.g., 10 1/2 inches). The calculator will output the precise number of stairs required, along with the exact rise and run for each step (for instance, a 7-inch rise and 10 1/2-inch run as shown). Based on your selected stringer attachment style, specific adjustments must be made when cutting the stringer: for inside mount stringers, remove the thickness of the outside joist from the inside of the top rise; for outside mount stringers, remove the thickness of the riser board from the back of the stringer. In both scenarios, the thickness of the tread board should be removed from the bottom of the stringer to ensure the first tread sits correctly on the landing.

Goal: Determine the precise rise, run, and number of steps, accounting for stringer attachment style and material thickness.

What's used

Tools

• Computer/Internet Access
• Pencil

About the full video

This project provides a comprehensive, step-by-step guide to constructing and installing deck stairs. It covers initial measurements, calculating rise and run for stringers, cutting the stringers, two methods for attaching stringers to the deck frame, and finally, installing the decking boards for treads and risers.

Step 1 of 6: Determine Stair Riser Height and Tread Depth

The first step in laying out deck stair stringers is to determine the optimal riser height and tread depth. The total rise is the vertical distance from the ground or landing to the deck surface. Divide the total rise by the desired number of risers to get the riser height. For example, if your total rise is 40 inches and you want 7 risers, each riser would be approximately 5.7 inches. Building codes often specify a maximum riser height (e.g., 7.75 inches) and a minimum tread depth (e.g., 10 inches). It's best to aim for consistency across all steps. The total run (or going) of the stairs is the horizontal distance covered by the treads. The formula for comfortable stairs is often cited as '2 * riser height + tread depth' should be between 24 and 25 inches. Calculate these values carefully to ensure safe and comfortable stairs.

Open this step in the guide

Every video in How to Lay Out and Cut Deck Stair Stringers

1. Step 1: Determine Stair Riser Height and Tread Depth

   • 0:06–1:32 Calculate Stair Dimensions
   • 0:19–0:57 Calculate Stair Dimensions and Stringer Type (this video)
   • 0:51–1:37 Calculate Individual Step Rise and Total Run

2. Step 2: Select Stringer Material

   • 0:00–0:03 Cut Stringers
   • 6:08–6:51 Stair Stringer Fabrication
   • 2:20–3:14 Mark and Cut Stringers

3. Step 3: Mark the First Stringer Layout

   • 3:10–3:59 Mark the Stringer Board
   • 6:59–9:34 Mark the Stair Stringer for Cutting
   • 6:12–7:01 Marking the Stringers

4. Step 4: Cut the First Stringer

   • 6:15–7:14 Cut Out the Stringer
   • 4:16–5:49 Cut Stringers
   • 15:12–19:27 Cutting the Stair Stringer

5. Step 5: Transfer Layout and Cut Additional Stringers

   • 8:43–8:58 Cutting Remaining Stringers using Template
   • 7:14–7:47 Replicate Stringers (Pattern Use)
   • 2:49–3:44 Layout and Cut Stringers

6. Step 6: Trim the Bottom of the Stringers

   • 7:25–10:59 Mark Top and Bottom Stringer Cuts
   • 7:30–8:22 Check and Adjust First Stringer
   • 8:10–9:35 Mark Top and Bottom Stringer Cuts