How to calculate tread and rise for stairs
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The requirements for the minimum depth of tread and maximum rise of steps for residential stairs in the UK are covered by section K (sometimes called "document K") of the building regulations. In the building regluations the "tread," which is the depth of each step, is called the "going.
" You will find a link to the relevant document in the Resources section.
Determine the minimum tread depth for the stairs. Section K specifies a minimum "going" of 220 mm (8 21/32 inch).
Determine the maximum rise for the stairs. Section K's maximum rise is the same as the minimum going -- 220 mm (8 21/32 inch).
Calculate the number of steps required to go from the floor to the top of the stairs. If the total rise of the stairs is 2.6 m (8 1/2 feet) and the maximum rise permitted by regs is 22 cm (8 21/32 inch), divide the total rise of the stairs by the rise permitted by code: 260 / 22 = 12 steps required to go from the floor to the top of the stairs.
Calculate the length of the floor space required for the stairs. If the minimum tread depth required by regs is 22 cm (8 21/32 inch), and 12 steps are required to go from the floor to the top of the stairs, multiply the minimum tread depth permitted by regs by the number of steps required by : 22 cm x 12 = 2.64 m (8 ft 715⁄16 in) of linear floor space required for the stairs.
- The maximum pitch allowed by the regulations for the staircase is 42 degrees.
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