A stair that will not fit the stairwell
At the first-floor design stage of a narrow two-storey house in Nicosia, the finished floor-to-floor height is 3.05 m. The stair rises from the ground-floor hall to a landing serving three bedrooms. The available stairwell is 0.95 m wide and 2.55 m long between finished wall faces. The ceiling opening can be extended by 0.60 m at the top but not at the bottom. The client is a retired couple who have asked for a comfortable, not steep, stair. The contractor proposes 16 risers at 190 mm with 15 goings at 170 mm, arguing that it fits the plan exactly. Building control will check riser and tread geometry, headroom and landing size.
1. Check the contractor’s proposal of 16 risers at 190 mm and 15 goings at 170 mm. Show the arithmetic and state whether you would accept it.
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The rise checks approximately: 16 × 190 mm = 3,040 mm, which is 10 mm short of the 3,050 mm floor-to-floor height, so the top riser would have to absorb the difference. The going is the problem. A 170 mm going is below normal comfortable practice; 2R + G = 2(190) + 170 = 550 mm, at the very bottom of the usual comfort range, and the short going forces a steep foot placement. The stair also fits only because the run is 15 × 170 = 2,550 mm, exactly the available length.
I would not accept it as a comfortable stair for retired clients. The design has been made to fit a number, not a body. It also leaves no tolerance for finishes, nosings or a slight setting-out error, and the 10 mm rise discrepancy is a warning that the stair has not been properly calculated.
2. Propose an alternative stair geometry that respects the 2.55 m available run and the client’s comfort requirement. Use calculations and describe what would have to change in the plan.
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A comfortable straight flight needs goings of about 250–280 mm. With 17 risers at about 179 mm, there are 16 goings; at 260 mm that requires 4.16 m, far more than 2.55 m. Even 16 risers at 191 mm with 15 goings at 250 mm needs 3.75 m. A dog-leg needs roughly 1.9 m of width for two 0.9 m flights, but the stairwell is only 0.95 m wide. A quarter-turn with winders can save some length, but three winders plus a short straight run in 2.55 m forces either very high risers or goings below about 220 mm.
The honest conclusion is that the stairwell is too small. I would extend it by borrowing 0.60–0.90 m from the adjacent hall or bedroom, or relocate the stair, then use 17 risers at 179 mm with 16 goings at 260 mm in an L-shaped or dog-leg arrangement. The drawing must show the revised floor opening, the landing of at least 0.95 m square, and the headroom check.
3. Explain how you would draw the stair on the ground-floor plan, first-floor plan and section at 1:50, including the break line, direction of travel and headroom check.
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On the ground-floor plan, cut the stair at about 1.0–1.2 m above floor level and show the flight rising away from the viewer. Use a diagonal break line beyond the cut, number the risers, and draw an arrow with “UP” from the bottom riser. Show the handrail and the newel; dimension the stairwell clear width and the first going. On the first-floor plan, show the flight arriving, the landing and the guarding; the break line is not needed in the same way, but the floor opening must be clear.
In section, draw the full flight and the floor opening, then measure headroom vertically from the nosing line to the underside of the floor or landing above. The usual minimum is about 2.00 m, but check the applicable requirement; a stair that passes under its own upper flight often fails here. Dimension the rise and going on one representative step, not on every step.