Risers and Treads

Question 1

Riser Height
Q: What is the minimum and maximum riser height for stairs in the US?

Answer 1

A:
- Minimum: 4 inches
- Maximum: 7-3⁄4 inches
- Spiral stairs maximum: 9-1⁄2 inches

Question 2

Riser Height
Q: How much variation is allowed in riser height within a flight of stairs?

Answer 2

A:
- No riser should exceed the smallest riser by more than 3/8-inch.

Question 3

Tread Depth
Q: What is the minimum required tread depth in the US?

Answer 3

A: 10 inches

Question 4

Tread Depth
Q: How is tread depth measured for winder stairs in the US?

Answer 4

A: At a 12-inch walk line, with a minimum of 6 inches at any point.

Question 5

Tread Depth
Q: How much variation is allowed in tread depth within a flight of stairs?

Answer 5

A: No tread should exceed the smallest tread by more than 3/8-inch.

Question 6

Spiral Stair Treads
Q: What are the requirements for spiral stair treads in the US?

Answer 6

A:
- All treads should be identical.
- Each tread should have at least a 7-1⁄2 inch depth at 12 inches from the narrower edge.

Question 7

Winder Stair Treads
Q: What are the requirements for winder stair treads in the US?

Answer 7

A:
- Treads should have a depth of at least 10 inches, measured 12 inches from the narrowest side.
- Treads should have a depth of at least 6 inches at any point.

Question 8

Stairway Slope
Q: What is the maximum allowed slope for stair treads and landings in the US?

Answer 8

A: 1 unit vertical in 48 units horizontal (1/4:12), or a 2% slope.

Question 9

Load Requirements
Q: What is the required load-bearing capacity of a stair tread in the US?

Answer 9

A: A 4 square inch area should be able to support a concentrated load of 300 pounds.

Question 10

Load Requiremenets
Q: What structural issues should be checked for on stair treads?

Answer 10

A: Look for cracks, damage, or loose treads.