Bounce in your step? Floors with too much deflection.
When you walk into the home do you hear the dishes rattling in the china cupboard?
On a recent home inspection I had just that. As I walked across the front room the cupboard rattled like an earthquake was happening. I could feel the deflection in the floor. Often this is just from too much deflection in the floor which is not uncommon, especially in some older homes. Even with code prescribed deflection it may still feel a little too bouncy or create squeaks.
Typical deflection limits that are referenced in code books are L/360, L/240 or L/180. These limits are based on live loads and the activities experienced in specific rooms of a home. Deflection is defined in the 2015 IRC R301.7 Deflection.
A few examples of code-prescribed deflection limits and live load values are:
Living room floors- L/360 & 40 psf
Bedrooms and habitable attic floors- L/360 & 30 psf
Attic floors with limited storage- L/240 & 10 psf
Now this may also depend on your exact flooring material.
The Tile Council of America recommends that deflection be limited to L/360 (L = span length in inches) under total load for ceramic tile. The Marble Institute of America recommends that total load deflection be limited to L/720 for spans up to 14‘-0″ and a maximum deflection of 7/32″ for spans greater than 14′-0”.
The deflection example is that a L/360 standard means that the floor should not deflect more than the “span” divided by 360. If the span of the joists is 10 feet (between supports), then the deflection should not be more than 1/3″ (0.333″) between the center and the end. With the same example of a 10 foot joist with a L/720 our allowable deflection would be 5/32″ (0.156″) for the same span.
So when using these materials such as tile you may need or want an even stiffer floor.
There are several methods to achieve a stiffer less bouncy floor such as sistering material to the floor or adding additional blocking. For more ways read the articles below for some ideas on how to approach that bounce in your step. Some may be easier than others and each situation will present their own challenges.
Here are a few articles from Fine Home Building, Prosales and This Old House that address this situation.
6 Ways to stiffen a bouncy floor — Fine Home Building
Stiffening Bouncy Floors – This Old House
Got Bounce Part 2: How to fix a floor deflection in an existing floor– Prosales magazine
If you find any errors or have additional information that would expand on any code, building standards or manufacturer requirements please let me know.
NCW Home Inspections, LLC is a Licensed Washington State Home Inspection service located in Wenatchee Washington serving Chelan County, Douglas County, Kittitas County, Okanogan County and Grant County Washington and the cities of Wenatchee, Leavenworth, Cashmere, Oroville, Cle Elum, East Wenatchee, Quincy and many more…
Your Wenatchee and Chelan Professional Real Estate, Home and Structural Pest Inspection Service
Coordinator & Instructor- Fundamentals of Home Inspection- Bellingham Technical College
Former WA Home Inspector Advisory Licensing Board
www.ncwhomeinspections.com 509-670-9572
You can follow me on Facebook, Twitter, Google+ and on my website Blog.
(Click on Icons to go to social media pages.)
