Problem: Floor Vibration - 3
Cause:
Inappropriate use of cantilevers.
Cantilevers can present problems for dining areas, kitchens, built-out china cabinets, and decks or landings. When a load is placed either on the main part of the floor or on the cantilever, the end of the cantilever will experience movement and vibration. Longer cantilevers result in weaker floor systems, which will experience more vibration.
Solutions:
Limit the extension of cantilevers:
- Most building codes limit the length of cantilevers when they are used to support roof loads. Cantilevers cannot support floor loads from other stories unless designed properly.
- When joists are cantilevered to accommodate bay windows, recessed china cabinets, extended dinettes, etc., there is a greater possibility that increased vibration will be evident in both the cantilevered section and the main section of the floor. When cantilevers are used, the length must not exceed building code maximums.
- In rooms that are enlarged by cantilevering the floor joists designers should consider using beams to carry roof loads across the openings. Loads are then transferred directly to the foundation with no impact on the floor system as shown in Figure 17.
Figure 17 - Reducing Loads On Cantilevers
- If cantilevers are going to be used, it is wise to use them in areas where loading and traffic will be light. Reducing loads on cantilevered joists will minimize the impact of the floor system and the potential for vibration will be reduced.