The thickness of these treads put over your existing stairs may cause a trip hazard because you are adding a full inch which may cause stumbles. Different counties have codes regarding changes in the rise of steps in relation to each other and with the landings at the bottom and top of a stair case. Most likely this application will be outside of code. These treads are designed to replace not go over existing steps.
Attention: Don't forget to check with your local building department to verify any building codes. This information could be incorrect or outdated. Building codes are updated regularly and to some building departments have different interpretations for certain building codes.
INTERNATIONAL STAIR CODE RESIDENTIAL
R311.5.3 Stair treads and risers.
R3188.8.131.52 Riser height.
The maximum riser height shall be 7-3⁄4 inches.
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.
R3184.108.40.206 Tread depth.
The minimum tread depth shall be 10 inches.
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.
Thank you for your inquiry.
Answered on 12/9/2011 by customer care 2