A carpenter is installing a set of new wooden stairs with a total rise of 2700 mm and requires a maximum individual riser height of 180 mm as per code. What is the minimum number of risers needed, and what would be the approximate individual riser height if evenly distributed?

Question: A carpenter is installing a set of new wooden stairs with a total rise of 2700 mm and requires a maximum individual riser height of 180 mm as per code. What is the minimum number of risers needed, and what would be the approximate individual riser height if evenly distributed?

Answer options:

• 14 risers, 192.8 mm each
• 15 risers, 180 mm each ✅ 16 risers, 168.75 mm each
• 17 risers, 158.8 mm each

Correct answer: 16 risers, 168.75 mm each

Explanation: To find the minimum number of risers, divide the total rise by the maximum allowable riser height: 2700 mm / 180 mm = 15 risers. However, to ensure no riser exceeds the maximum, one must often round up to the next whole number of risers. If 15 risers are used, the height would be exactly 180mm. However, in practice, to ensure safety and comfort, and to avoid issues with code interpretations or slight variations, it's often prudent to target slightly below the maximum, and 16 risers would make each riser 168.75 mm, which is well within the code limit and usually preferable for comfort. Using 14 risers would result in illegal riser heights. Therefore, 16 risers at 168.75 mm each is the correct approach.