How To Build Stringers For Deck Stairs
Constructing stringers for deck stairs is a foundational element in creating safe and functional outdoor access. This process involves precise measurements and careful execution to ensure structural integrity and adherence to building codes. The following steps detail the procedure for building stringers, providing a guide for accurate and reliable construction.
Planning and Measurement
The initial phase involves meticulous planning and accurate measurement. The precision at this stage directly impacts the final product's safety and usability.
Determining Rise and Run
Rise refers to the total vertical height of the stairs, measured from the top of the deck surface to the final grade level. This measurement dictates the overall height of the staircase. Run indicates the total horizontal distance the staircase will cover. Accurate determination of both rise and run is critical before any cutting begins.
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For example, if the deck is 42 inches above the ground, the total rise is 42 inches.
Next, calculate the individual rise and run for each step. Building codes often specify acceptable ranges for these dimensions. A common guideline is that the sum of the rise and run should fall between 17 and 18 inches. Individual rise is calculated by dividing the total rise by the number of steps. Individual run is calculated by dividing the total run by the number of steps.
If a staircase has a total rise of 42 inches and is planned to have 6 steps, the individual rise will be 7 inches (42 inches / 6 steps = 7 inches per step).
Calculating Stringer Length
The stringer length determines the quantity of lumber needed. The Pythagorean theorem is employed to calculate the stringer length. The formula is a2 + b2 = c2, where a represents the rise, b represents the run, and c represents the stringer length. Calculate for the single step. Then, multiply the hypotenuse by the number of steps to determine the total length.
If the individual rise is 7 inches and the individual run is 10 inches, the hypotenuse (length of the stringer for that single rise and run) would be approximately 12.2 inches (√(72 + 102) ≈ 12.2 inches). For 6 steps, the calculation would be repeated for the entire length of the stringer, not multiplied. The total rise (42 inches) and total run (60 inches) are used to calculate the stringer length from the deck to the ground. The stringer length would be approximately 73.49 inches (√(422 + 602) ≈ 73.49 inches). This calculation will allow you to determine the quantity of the lumber required.
Cutting the Stringers
Once measurements are confirmed, the physical cutting of the stringers can commence.
Marking the Stringers
Transfer the rise and run measurements onto the lumber using a stair gauge and a framing square. A stair gauge consists of two small metal pieces that attach to a framing square to mark the rise and run accurately. Align the stair gauges with the previously determined rise and run values. Trace along the framing square to create the outline of each step.
For instance, if the rise is 7 inches and the run is 10 inches, attach the stair gauges to the framing square at these measurements. Position the framing square on the lumber and trace the outline of the first step. Repeat this process, moving the framing square along the lumber, ensuring each step aligns precisely with the previous one.
Cutting the Notches
Use a circular saw to cut along the marked lines. Exercise caution to avoid cutting beyond the lines, as this can compromise the structural integrity of the stringer. It is recommended to set the saw blade depth slightly less than the lumber's thickness to prevent overcutting.
To avoid overcutting, set the saw blade depth to, for instance, 1.4 inches if the lumber is 1.5 inches thick. After making the initial cuts with the circular saw, use a handsaw or jigsaw to complete the cuts in the corners, ensuring clean and precise removal of the waste material.
After cutting out the notches, inspect the stringers for any defects or inconsistencies. Sand down any rough edges or splinters to create a smooth surface. This not only improves the appearance of the stringers but also enhances safety by preventing splinters.
Accounting for Decking Thickness
Adjust the top riser cut on the stringer to account for the thickness of the decking material. This adjustment ensures that the top step is flush with the deck surface, preventing a tripping hazard. Measure the thickness of the decking material and subtract this value from the top riser measurement on the stringer.
If the decking material is 1 inch thick, reduce the top riser measurement by 1 inch. This adjustment ensures that the top step will be level with the deck surface once the decking is installed.
Installation
With the stringers prepared, the next phase involves their secure installation.
Attaching the Stringers to the Deck
Securely attach the stringers to the deck frame using appropriate fasteners, such as lag screws or structural screws. Ensure that the stringers are properly aligned and evenly spaced. Use a level to verify that the stringers are plumb and square.
When attaching the stringers to the deck, use at least two lag screws or structural screws per stringer. Pre-drilling pilot holes helps to prevent the wood from splitting. Space the stringers evenly, typically 16 inches on center, to provide adequate support for the stair treads.
Securing the Bottom of the Stringers
The bottom of the stringers must rest on a stable and level surface, such as a concrete footing or a properly prepared gravel base. This ensures that the stairs are stable and prevents settling over time. If using a concrete footing, attach the stringers using anchor bolts or similar fasteners.
When preparing a gravel base, ensure that it is compacted and level. Use landscape fabric to prevent weed growth and maintain the integrity of the base. Attach the stringers to the base using pressure-treated lumber and appropriate fasteners.
Adding Support
Depending on the height and length of the staircase, additional support may be necessary. This can include adding a center stringer or installing posts to provide extra stability. A center stringer is particularly useful for wider staircases, as it helps to prevent flexing or sagging of the treads.
For staircases wider than 4 feet, consider adding a center stringer. Secure the center stringer to the deck frame and the base using the same methods as the outer stringers. Install posts along the sides of the staircase to provide additional support, especially for taller staircases.
Final Considerations
After installing the stringers, inspect the entire structure for any weaknesses or inconsistencies. Make any necessary adjustments or reinforcements to ensure that the stairs are safe and stable.
Building Codes and Regulations
Adherence to local building codes is imperative. Familiarize yourself with the specific regulations regarding stair construction in your area. These codes often specify requirements for rise, run, handrails, and other safety features. Failure to comply with building codes can result in fines or the need to redo the work.
Material Selection
Select high-quality, pressure-treated lumber for the stringers. Pressure-treated lumber is resistant to rot and insect damage, ensuring the longevity of the staircase. Ensure that the lumber is properly dried and free from defects, such as knots or cracks.
Finishing Touches
Once the stringers are securely installed and the treads are in place, consider adding finishing touches to enhance the appearance and safety of the staircase. This may include installing handrails, painting or staining the wood, or adding decorative elements.
By following these steps with precision and attention to detail, you can construct sturdy and reliable stringers for deck stairs, ensuring safe and convenient access to your outdoor space.
