Floor Deflection Limits

Deflection limits for floor trusses copyright 2016 page 4 of 9 background.
Floor deflection limits. On center systems these floors often have deflection between the joists exceeding l 360. Allowable deflection is generally expressed as a fraction of the span in inches. These limits are based on live loads and activities experienced in specific rooms of a house. For example while joist manufacturers regularly meet the standard l 360 criteria for code construction with 24 o c.
Maximum deflection limits are set by building codes. Vertical deflection limits are given in table na1 examples of limiting values of vertical deflections. All structural members will deflect or flex under load. 107 2 1 information on construction documents.
Drywall attached to the underside of this system is not expected to crack when the floor joist system. Typical deflection limits referenced in code books are l 360 l 240 or l 180. Bedrooms and habitable attic floors l 360 30 psf. Construction documents shall be in accordance with sections 107 2 1 through 107 2 6.
Living room floors l 360 40 psf. They are clearly more onerous than the suggested limits given in table 8 of bs 5950 1. Typically for better performing floors minimal defection is desired. The ibc is fairly specific about the information required on construction documents.
The values from a few categories in table na1 are given in table 1. Deflection limit state last revised. 11 04 2014 in the absence of more specific criteria criteria for structures with brittle finishes as found in code documents for years is frequently used. The values in this table are for the total deflection from dead plus live loads permanent plus variable loads in eurocode terminology.
Structural member allowable deflection rafters having slopes greater than 3 12 with no finished ceiling attached to rafters l 180 interior walls and partitions h 180 floors including deck floors ceilings with plaster or stucco finish l 360 ceilings with plaster or stucco finish l 360 ceilings with gypsum board or other flexible finishes l 240 all other structural members l 240 exterior walls. 2000 which are calculated for imposed load only three of which are given in table 2. Examples of code prescribed deflection limits and live load values are. The amount of flex depends on the magnitude of the load applied span of the member and stiffness of the member.