Formula Used
Total risers = ceiling(total rise / preferred riser). The value is made even, so both flights have equal risers.
Actual riser = total rise / total risers. Treads per flight = risers per flight - 1.
Going per flight = treads per flight × tread. Stair angle = tan⁻¹(actual riser / tread).
Comfort check = 2 × riser + tread. Required width = two flight widths + well gap.
Waist load = concrete density × waist slab thickness / cosθ. Step load = concrete density × riser / 2.
Service load = waist load + step load + finish load + live load. Factored load = service load × load factor.
Moment per metre strip = wuL² / 8. Shear per metre strip = wuL / 2.
Effective depth = slab thickness - cover - half bar diameter. Main steel is found from the flexural resistance equation.
How to Use This Calculator
Enter the finished floor height first. Add your preferred riser and tread sizes. Enter clear width, landing length, and well gap.
Add available stairwell dimensions to check whether the layout fits. Then enter slab thickness, loads, material grades, cover, and bar sizes.
Press Calculate. The result appears below the header and above the form. Review comfort checks, plan size, loads, moments, and suggested reinforcement.
Use the CSV button for spreadsheet records. Use the PDF button for a compact site summary.
Design Notes for Dog Legged Stairs
A dog legged staircase turns one hundred eighty degrees between two flights. It saves floor area and gives a compact access path. The landing works as a turning platform. Good design needs comfort, strength, and clear movement. This calculator joins layout checks with a simple slab design strip. It is useful during early planning, quantity review, and site coordination.
Comfort and Layout
Comfort begins with the riser and tread. A low riser is easier to climb. A deep tread gives better foot support. The common rule is two risers plus one tread. The result should stay within a practical walking range. The tool also checks the stair angle. A steep flight may fit the opening, but it can feel unsafe.
The layout section estimates total risers, equal risers per flight, treads per flight, landing size, total run, stairwell width, and plan length. It also shows whether the entered opening can receive the calculated stair. This helps designers compare available space before drawings are fixed.
Loads and Reinforcement
The structural part treats each flight as a one metre design strip. It includes waist slab weight, step concrete, finish load, and live load. The factored load gives bending moment and shear. Required main steel is compared with minimum slab steel. Bar spacing is then suggested from the selected bar diameter. Distribution steel is also listed.
The output should be checked against local codes, architectural details, support conditions, and engineer review. Real stairs may have beams, folded plates, wall supports, or different landing actions. Openings, headroom, railing space, finishes, and fire requirements can change final dimensions. Use the result as a clear design guide, not as a final sealed drawing.
Site Review
Before using the numbers, confirm the floor finish level at both ends. Include tiles, bedding, screed, and any nosing detail. Small errors in floor height can change every riser. Keep all risers equal on site. Unequal risers are a common trip hazard.
For concrete stairs, reinforcement should follow the support direction. Main bars usually run along the flight span. Extra top bars may be needed over supports and landings. Check anchorage into beams or walls. Also review crack control, cover, durability, and construction joints. A neat calculation helps discussion with architects and site teams before work starts on site.
FAQs
What is a dog legged staircase?
It is a stair with two flights running in opposite directions. A landing connects both flights. It is common in compact residential and commercial buildings.
Why does the calculator make risers even?
A dog legged stair usually needs equal risers in both flights. An even riser count keeps both flights balanced and easier to detail.
What is a comfortable riser size?
Many stairs use risers between 150 mm and 175 mm. The right value depends on code, building type, and available space.
What tread depth should I use?
A tread near 250 mm to 300 mm is common. Deeper treads improve footing, but they also increase the required stairwell length.
Does this tool design reinforcement?
It gives a preliminary one metre strip design. It estimates bending steel and spacing. A qualified engineer should verify final reinforcement.
Can I use this for steel stairs?
This calculator is mainly for concrete waist slab stairs. Steel stairs need member sizing, connection checks, and different load paths.
Why is the landing included?
The landing provides the direction change. Its length also affects the total plan size and user safety during turning movement.
Are these results final for construction?
No. Use them for planning and checking. Final drawings must follow local codes, project loads, detailing rules, and engineer approval.