Basic Rules for Stair Design: A DIY Guide 2026

When designing a staircase, there are many considerations for individual cases, but the basic rule remains: 2a + p = 60~65 cm (where a = riser height, p = tread depth).

Design-wise, a steep staircase is necessary when there isn't enough horizontal length. To save space, you can consider the upper floor landing as the last tread: the staircase will then have one more riser than the number of actual treads. If space is still tight, meaning the incline exceeds 45°, you'll need to opt for an angled or L-shaped design.

For spiral staircases, a different approach is needed: the trapezoidal shape of the tread means it must be measured along the walking line, about 30 cm from the handrail.

Small-diameter spiral stairs are inherently steep because you must maintain a 2-meter height clearance between a step and the corresponding step of the turn above. Since you can't fit more than 12 steps per turn without making treads too shallow, the risers will be significantly higher than on straight stairs. For larger diameters, it's easier to follow the formula above.

Regulations and the "Rule of the Step"

The regulations governing private-use stairs (UNI 10800) establish the optimal measurements for a well-designed staircase. A person of average height covers about 60-65 cm with each step on an inclined plane, and this length must equal the sum of two risers plus one tread: if one of these dimensions increases, the other must decrease to keep the total within that range. DIYers must scrupulously follow this "rule of the step." For example:

• Tread 29 cm + 17 cm x 2 risers = 63 cm (30° incline)
• Tread 21 cm + 21 cm x 2 risers = 63 cm (45° incline)

When planning your home improvement project, remember that a staircase enclosed between two walls is less common in contemporary architecture. If no natural light source is available, it will appear dark and gloomy, so you'll need to compensate with good lighting. Even when laterally protected, it must still have a handrail on at least one side for support during ascent and descent.

If the staircase is against a wall, it communicates with the surrounding environment and draws light from it, except at the top; it must be equipped with a railing and handrail on the open side. In the absence of any adjacent walls—completely open—a railing or parapet becomes essential on at least one side, and outdoor lighting or artificial illumination is crucial.

Frequently Asked Questions

Q: What is the ideal stair slope?
A: The ideal slope for a comfortable staircase is between 30° and 35°. Steeper slopes (up to 45°) are acceptable for space-saving designs like spiral or alternating tread stairs, but they are less comfortable for daily use.

Q: Can I build a staircase myself?
A: Yes, many DIYers successfully build stairs using pre-cut stringers and home improvement tools. However, precise measurements and local building codes must be followed strictly for safety.

Q: How many steps can I have in a single flight?
A: For private homes, a single flight should ideally have no more than 12-15 steps before a landing. Longer flights can be tiring and increase the risk of falls.

Q: What materials are best for stair treads?
A: Hardwoods like oak, maple, or cherry are popular for durability and appearance. For outdoor stairs, consider treated lumber or composite materials. You can also explore garden supplies for outdoor stair projects.

Q: Do I need a handrail on both sides?
A: Building codes typically require at least one handrail for stairs wider than 1 meter. For wider stairs (over 1.5 meters), handrails on both sides are recommended. Check local regulations for specific requirements.

For your staircase project, consider complementing your design with rugs for added safety and style, or wall decor to enhance the surrounding area. If your staircase leads to an outdoor space, browse our selection of outdoor patio furniture and outdoor decor to create a seamless transition.

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