Stairs: It they don’t feel right then they probably aren’t 

Stairs are among the many fundamental components of a building that are quite important, but often not built correctly.

Whether the building is a single family dwelling, or a commercial building, the stairs are usually a part of the ‘means of egress’ from the building.

Some have argued that the stairs in their home should be allowed as steep as they want.

Actually they can be if the stairs are to access a storage loft, attic or some other space not used as habitable space.

The primary stairs, the ones providing access to and from any kind of habitable space, have very specific maximum and minimum dimensional requirements.

There are two basic features of stairs, rise and run.

To measure the run (depth) use a horizontal distance from the face of one riser to the face of the next, or from the edge of one nosing to the edge of the next.

The nosing is always added to the tread depth which then determines walking surface.

The rise is measured from one horizontal surface to the next, including each floor level.

Straight from the Residential Code of NY…

Section R311.5 Stairways… R311.5.1 Width: Stairways shall not be less than 36 inches (914 mm) in clear width at all points above the permitted handrail height and below the required headroom height.

Handrails shall not project more than 4.5 inches (114 mm) on either side of the stairway and the minimum clear width of the stairway at and below the handrail height, including treads and landings, shall not be less than 31.5 inches (787 mm) where a handrail is installed on one side and 27 inches (698 mm) where handrails are provided on both sides.

R311.5.2 Headroom. The minimum headroom in all parts of the stairway shall not be less than 6 feet 8 inches (2036 mm) measured vertically from the sloped plane adjoining the tread nosing or from the floor surface of the landing or platform.

R311.5.3.1 Riser height. The maximum riser height shall be 8 ? inches (209 mm). The riser shall be measured vertically between leading edges of the adjacent treads. The greatest riser height within any flight of stairs shall not exceed the smallest by more than 3/8 inch (9.5 mm).

R311.5.3.2 Tread depth. The minimum tread depth shall be 9 inches (229 mm).

The tread depth shall be measured horizontally between the vertical planes of the foremost projection of adjacent treads and at a right angle to the tread’s leading edge.

The greatest tread depth within any flight of stairs shall not exceed the smallest by more than 3/8 inch (9.5 mm).

Winder treads shall have a minimum tread depth of 10 inches (254 mm) measured as above at a point 12 inches (305 mm) from the side where the treads are narrower.

Winder treads shall have a minimum tread depth of 6 inches (152 mm) at any point.

Within any flight of stairs, the largest winder tread depth at the 12 inch (305 mm) walk line shall not exceed the smallest by more than 3/8 inch (9.5 mm).

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Open risers are permitted, provided that the opening between treads does not permit the passage of a 4-inch diameter (102 mm) sphere. This is the same test that applies to the distance between spindles for hand railings or guards.

Some of the most common errors made when calculating stairs are: not using the correct overall height to determine equal risers, trying to use the nosing as part of the run, remembering the thickness of the tread at the first and last riser.

Another common problem is that the minimum headroom of 6’8” is not maintained.

Usually this is from not leaving a large enough stairwell opening in the floor. It takes careful planning in tight spaces to build compliant stairs.