For a house in Nepal, the National Building Code NBC 206:2015 sets the stair limits: a riser of 190 mm (about 7.5 inches) or less, a tread of 250 mm (about 10 inches) or more, a clear width of at least 0.9 m, no more than 15 risers in one flight, at least 2 m headroom, and a handrail 900 mm above the tread. To find the number of steps, divide the floor-to-floor height by your target riser and round up. For a 3.0 m floor height and a 175 mm target riser that gives 18 risers of 166.7 mm, which suits a dog-legged stair with two flights of 9.
This guide gives the code values, a step-by-step method, three worked examples with Nepali floor heights, a quick table, the concrete quantity for a typical dog-legged stair, and the mistakes we see most often on house sites. If you only need the numbers, use the free stair calculator.
NBC 206 staircase rules for houses
NBC 206:2015 (Architectural Design Requirements) is the Nepal code that covers stairs. Its Table 4 gives the step dimensions and Table 3 gives minimum widths by building type. The values below are taken from the code published by the Ministry of Urban Development.
| Item | Residences | Other buildings |
|---|---|---|
| Maximum riser | 190 mm (7.5 in) | 175 mm (6.9 in) |
| Minimum tread (going) | 250 mm (10 in) | 279 mm (11 in) |
| Maximum risers per flight | 15 | 15 |
| Minimum headroom | 2.0 m (6 ft 6 in) | 2.0 m |
| Handrail height above centre of tread | 900 mm (3 ft) | 900 mm |
Minimum stair width by building type
| Building type (NBC 206 Table 3) | Minimum clear width |
|---|---|
| General residence (house) | 0.9 m |
| Residence with limited commercial use | 1.0 m |
| Apartments and dormitories | 1.2 m |
| Commercial, office, storage | 1.25 m |
| Commercial or office, medium and high rise | 1.5 m |
| Secondary school | 1.5 m |
| Hospital and clinic | 1.8 m |
Stairs used only to reach a loft, attic or terrace may be as narrow as 600 mm under the code, but for a family house a 900 mm to 1,000 mm stair to the terrace is far easier to use and lets you carry a water tank or furniture up. Municipalities also apply their own building bylaws during naksa pass, so confirm the width and any fire-exit rule with your municipality's engineering section before you fix the plan.
The comfort check: 2R + T
The code gives limits, not the best size. A stair is comfortable when twice the riser plus the tread is close to a normal walking stride. Designers use 2R + T = 600 to 640 mm as the target, and 550 to 700 mm as the acceptable band. A 190 mm riser with a 250 mm tread gives 630 mm, which passes the check but feels steep for older people. A 165 to 175 mm riser with a 250 to 300 mm tread is what most comfortable house stairs in Nepal use.
How to calculate a staircase: step-by-step method
- Measure the floor-to-floor height (H) from finished floor to finished floor, not slab top to slab top. If the floor finish is not laid yet, add the planned screed and tile thickness at both levels.
- Pick a target riser. Use 150 to 175 mm for comfort. Never exceed 190 mm in a house.
- Number of risers n = H / target riser, rounded up. For a dog-legged stair with two equal flights, make n even.
- Actual riser R = H / n. Every riser in the stair must be this same height.
- Choose the tread T so that 2R + T falls between 600 and 640 mm, and T is at least 250 mm.
- Number of treads in a flight = risers in that flight minus 1, because the last riser steps onto the landing or floor. Going of a flight = treads x T.
- Check the 15-riser rule. If a single flight has more than 15 risers, add a landing.
- Size the stair hall. Length = going + landing depth (keep the landing at least as deep as the stair is wide). Width = 2 x flight width + gap between flights for a dog-legged stair.
- Check headroom under every beam and the upper flight: at least 2.0 m measured vertically from the nosing line.
Worked example 1: dog-legged stair for a 3.0 m floor height
This is the most common stair in a two or three storey RCC house in Kathmandu valley: floor-to-floor height 3.0 m (about 9 ft 10 in), two flights with a half landing, flight width 1.0 m.
- Target riser 175 mm: n = 3000 / 175 = 17.14, round up to 18 risers (already even).
- Actual riser R = 3000 / 18 = 166.7 mm (about 6.6 in).
- Each flight: 9 risers, so 8 treads.
- Try T = 250 mm: 2R + T = 333.3 + 250 = 583 mm, below the 600 mm target. The stair would feel short-stepped.
- Try T = 275 mm: 2R + T = 333.3 + 275 = 608 mm. Good.
- Going of each flight = 8 x 275 = 2.2 m.
- Stair hall length = 2.2 m going + 1.0 m landing = 3.2 m clear (plus floor space at the top and bottom of the flights).
- Stair hall width = 1.0 + 1.0 + 0.1 m gap = 2.1 m clear.
So a 2.1 m x 3.2 m clear stair hall, or about 7 ft x 10 ft 6 in, holds a comfortable dog-legged stair for a 3.0 m storey. If the plan only allows 2.0 m of going, you must either accept a 250 mm tread (2R + T = 583 mm) or raise the riser, and both make the stair less pleasant.
Worked example 2: straight stair for a 2.85 m floor height
A narrow house on a 4 aana plot often has a straight stair along one wall. Floor-to-floor height 2.85 m (9 ft 4 in).
- At the code maximum riser of 190 mm: n = 2850 / 190 = 15 risers of exactly 190 mm, 14 treads. This is allowed in a single flight (15 is the limit). With T = 250 mm, 2R + T = 630 mm and the going is 14 x 0.25 = 3.5 m. It is legal but steep.
- At a comfortable 175 mm target: n = 2850 / 175 = 16.3, so 17 risers of 167.6 mm. That is more than 15, so a single flight is not allowed. Split it into flights of 9 and 8 risers with a landing.
- With T = 275 mm: 2R + T = 335.3 + 275 = 610 mm. Treads = 8 + 7 = 15, going = 15 x 0.275 = 4.125 m, plus a 0.9 m landing = 5.03 m of wall length.
The choice is between 3.5 m of wall with a steep stair and 5.0 m with a comfortable one. That is why the stair should be fixed at the planning stage, before the column grid is decided.
Quick table: number of risers for common floor heights
Values are rounded to 0.1 mm. "Dog-legged" rounds the count up to an even number so both flights are equal.
| Floor-to-floor height | Target 175 mm: risers (R) | Target 190 mm: risers (R) | Dog-legged, 175 target | Dog-legged, 190 target |
|---|---|---|---|---|
| 2.75 m (9 ft) | 16 (171.9 mm) | 15 (183.3 mm) | 16 (171.9 mm) | 16 (171.9 mm) |
| 2.85 m (9 ft 4 in) | 17 (167.6 mm) | 15 (190.0 mm) | 18 (158.3 mm) | 16 (178.1 mm) |
| 3.00 m (9 ft 10 in) | 18 (166.7 mm) | 16 (187.5 mm) | 18 (166.7 mm) | 16 (187.5 mm) |
| 3.05 m (10 ft) | 18 (169.4 mm) | 17 (179.4 mm) | 18 (169.4 mm) | 18 (169.4 mm) |
| 3.20 m (10 ft 6 in) | 19 (168.4 mm) | 17 (188.2 mm) | 20 (160.0 mm) | 18 (177.8 mm) |
| 3.35 m (11 ft) | 20 (167.5 mm) | 18 (186.1 mm) | 20 (167.5 mm) | 18 (186.1 mm) |
Any count above 15 needs at least two flights. For a 10 ft storey the usual answer is 18 risers of about 169 mm, 9 in each flight.
Worked example 3: concrete quantity for the dog-legged stair
Owners and site engineers often need the concrete for the stair when ordering cement. Take the stair from example 1 (R = 166.7 mm, T = 275 mm, 8 treads per flight, width 1.0 m) with a 150 mm waist slab and a 2.1 m x 1.0 m x 150 mm landing. The 150 mm waist is only an example; use the thickness from your structural drawing.
| Part | Calculation | Volume |
|---|---|---|
| Inclined length of one flight | 2.2 m x square root of (1 + (166.7 / 275) squared) = 2.2 x 1.169 | 2.573 m |
| Waist slab, one flight | 2.573 x 1.0 x 0.15 | 0.386 m3 |
| Steps, one flight | 8 x (0.1667 x 0.275 / 2) x 1.0 | 0.183 m3 |
| Two flights | 2 x (0.386 + 0.183) | 1.138 m3 |
| Landing | 2.1 x 1.0 x 0.15 | 0.315 m3 |
| Total wet concrete | 1.45 m3 |
For M20 (1 : 1.5 : 3) using the same method as our cement bags for 1 m3 of M20 guide: dry volume = 1.45 x 1.54 = 2.24 m3. Cement = 2.24 / 5.5 x 1440 = 586 kg, or about 11.7 bags (order 12). Sand = 2.24 x 1.5 / 5.5 = 0.61 m3 (about 21.6 cft) and aggregate = 2.24 x 3 / 5.5 = 1.22 m3 (about 43.1 cft). You can check other sizes with the concrete calculator. The steel for the waist slab is taken from the bar bending schedule, in the same way as in the RCC slab quantity example.
Common mistakes on Nepali house sites
1. Forgetting the floor finish
The steps are cast to equal heights from slab level, then the ground floor gets 50 mm of screed and tile while each tread gets only 20 mm of tile. The first riser ends up 30 mm shorter than the rest, and people trip on it. Work out risers from finished floor levels and adjust the first and last step during casting.
2. Squeezing in winders or an extra step
When the stair hall is too short, masons add tapered winder steps at the landing or one extra riser at the top. Unequal steps are the main cause of falls on house stairs. Fix the stair hall size on the drawing first, then the room sizes around it.
3. Low headroom under a beam
A 230 x 350 mm beam across the stair hall at the upper floor can cut the headroom below 2.0 m over the last few steps of the lower flight. Check headroom on the section drawing, and move or raise the beam before the formwork goes up.
4. Steep terrace stair
The stair to the terrace is often built with 200 to 230 mm risers to save space. It is used every day for water tanks, washing and solar heaters, so keep it within the same 190 mm limit as the rest of the house.
5. Missing or low handrail
Many houses are occupied with no handrail for years. Fix at least a temporary rail at 900 mm, and a parapet or railing at landings and the open side of the stair well, before family members start using the upper floor.
6. Tread measured to the nosing projection
The tread (going) is measured horizontally from one riser face to the next. A 25 mm nosing projection does not add to the going. If you count it, a 250 mm drawing tread becomes a 225 mm real tread, below the code minimum.
Frequently asked questions
What is the standard stair size for a house in Nepal in feet?
A comfortable house stair uses a riser of about 6.5 to 7 inches and a tread of 10 to 11 inches, with a clear width of 3 to 3.5 ft. The code limits are a 7.5 inch (190 mm) maximum riser, a 10 inch (250 mm) minimum tread and a 3 ft (0.9 m) minimum width.
How many steps are needed for a 10 ft floor height?
10 ft is about 3.05 m. With a 175 mm target riser you need 18 risers of 169.4 mm, which is 9 in each flight of a dog-legged stair. Each flight then has 8 treads.
Is a spiral stair allowed?
In a house it can serve as a second stair, for example to a terrace. NBC 206 does not allow a spiral stair to be counted as the means of exit in medium-rise buildings, so do not rely on one as the main stair.
Does the municipality check the stair during naksa pass?
The stair is part of the plan and section drawings submitted for the permit, and the municipality checks it against the code and its bylaws. Rules and how strictly they are checked vary between municipalities, so confirm with your local office.
What waist slab thickness should I use?
It depends on the span of the flight, its support conditions and the loads, so it must come from the structural design. Do not copy a thickness from a neighbouring house with a different span.
Related tools and guides
- Stair calculator for risers, treads and concrete volume
- Standard room, door and window sizes in Nepal
- All free engineering tools
- Civil engineering MCQ practice for NEC and Lok Sewa preparation
Sources
- NBC 206:2015 Architectural Design Requirements, Ministry of Urban Development, Government of Nepal (Tables 3 and 4)
- Department of Urban Development and Building Construction, which publishes the Nepal National Building Codes
- IS 456:2000 Plain and Reinforced Concrete, clause 33 on the design of stairs
Values in this article are for planning and estimating. Your municipality's bylaws and the structural engineer's drawings take priority for any building.
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