Designing stairways is not just a matter of aesthetics. A functional staircase is the work of meticulous geometry, precise calculations, and safety guidelines. A staircase with risers that are too high or too low, or treads that are too wide or too narrow, will not be easy to climb. Ergonomic design principles are crucial for all staircases to prevent injuries and accidents. Computer programs and online tools can simplify the math, but precision and care are essential.
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Things you need
- Computer-Aided Drafting (CAD) software (optional)
- Drafting paper
Draft a plan for the stairway. You can do this manually with drafting paper, a calculator, and a ruler, or you can purchase CAD software. Another option is to purchase software online designed for making stairway calculations, or to use a free online calculator. Begin drafting by selecting the placement for the staircase, then move on to the calculations required to design the stairs.
Determine the necessary rise for each step of the staircase. Consult local building codes to determine preferred measurements or minimums for each riser. The International Residential Code, developed for one- and two-family dwellings of three stories or less, specifies that risers should be no more than 7-3/4 inches high.
Divide the total height the staircase will span by the desired height of each riser to determine the number of steps for the staircase. For example, a staircase spanning 7 feet, or 84 inches, with a desired height of 6 inches per riser, yields 14 steps total. Draw, measure and mark this total on drafting paper or computer software.
Determine the thickness of each stair tread. For simplicity, include the thickness of the tread in the total riser height. Building inspectors will measure from the top of each tread, so the thickness of the treads are included in the total riser height. The Typical thickness for stair threads is 1 inch. Measure and mark the locations of each stair tread on drafting paper or computer software.
Measure and mark the thickness of each stair tread to determine placement of the horizontal cut lines that will be marked on the stair stringers. Stair stringers are the zigzag-shaped forms that support each tread and riser on either side, creating the backbone of the staircase.
Determine the location of the outer front surface of the top riser, and locate the front edge of the first tread. Measure and mark on drafting paper or computer software.
Determine the depth of each tread. Consult local building codes for tread depth requirements. The International Residential Code specifies a minimum depth of 10 inches for stair treads. Allow room for the tread to overhang the riser by about one inch. Subtract the overhang of the tread to determine the location of the next riser. Measure and mark tread depth and overhang on drafting paper or computer software.
Subtract the thickness of each riser to determine the vertical cut line for the stair stringers. Typical riser thickness is usually between 3/4 inch and 1 inch. Measure and mark on drafting paper or computer software. Repeat calculations for measurement of treads and risers for each step of the staircase.
Determine tread width. Consult local building codes for tread width requirements. The International Residential Code specifies a stairway width of at least 36 inches.
Calculate headroom for the stairway. Consult local building codes for requirements. The International Residential Code specifies at least 80 inches of headroom for the full width of the stairway and landing, measured vertically from the slope of the stairs.
Draft other design features as needed, such as handrails, and consult local building codes for requirements on handrail height and other requirements. The International Residential Code specifies continuous handrails on at least one side of the staircase for flights of stairs with four or more risers.
Tips and warnings
- Check with your local building inspector for local building codes regarding single-family construction for additional guidelines on stairways. The International Residential Codes are a common standard employed by many states, but local codes may vary.
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