Armchair Builder

Repairing Bouncy Floors

Armchair Builder recently answered a reader question on repairing bouncy floors so we thought we might share it with the rest of you.  Even if you don’t have floors that move too much now, knowing more about what causes the problem can help to prevent issues on future building projects.  When we say “bouncy” we’re talking about the amount of deflection in the floors.  Meaning, when someone walks across the surface, the live load created from the weight of the person causes the framing below the floor to move downward more than you would like.  So what are some of the common causes of this issue and how can they be fixed?  Are floor squeak more of the issue in your home?  You can find more information on floor squeaks in our video on floor squeak repair and prevention.

Root Causes of Excessive Floor Deflection

Before we can start repairing bouncy floors in a home, it’s important to understand what causes them.  In some cases, it’s purely an economical issue.  Whomever designed the floor framing system when the addition or home was built may have stretched the spans and spacing of the support to it’s limits to save money.  This is fine from a structural standpoint.  Meaning, the floor will safely support live loads (people and animals) and dead loads (furniture, finished flooring…etc.) adequately without the potential for failure.  But from a comfort point of view, too much deflection in the floor can be a nuisance to homeowners.  Why?  Because china cabinets, collectibles, and other personal items can shake so violently when someone walks across the room that damage can occur.  Excessive movement in the framing below can also cause damage to tile and grout in the finished flooring.  In some cases, the homeowner is forced into repairing bouncy floors to prevent further damage.

Another common cause of excessive floor deflection is misplaced or inadequate bracing in the floor system.  Floor framing systems are made up of several different structural components these days including open web trusses, manufactured I-joists, and traditional dimensional lumber (i.e. 2×10’s or 2×12’s).  Each of these types of floor framing systems can in many cases require bracing to stiffen up the structure.

Repairing Bouncy Floors

In most cases, repairing bouncy floors is no easy task.  But if you have an unfinished basement or a basement with a drop ceiling, you just might have enough access to stiffen up the floor from below.  Let’s take a look at some of the different options for stiffening up a floor from below for each of the possible floor system types.

Open Web Floor Trusses – Most open web floor truss systems require bracing with 2×4 or 2×6 members that tie the trusses together so they work together.  The idea is to allow the trusses next to the one bearing most of the weight to help out.  Here are some tips for repairing bouncy floors in open web floor truss systems by adding bracing.

  • Use the longest 2×6 possible.  The longer the brace, the more trusses that will be tied together and the stiffer the floor will become.
  • If using a 2×6 brace, make sure the 5.5 inch length of the member is vertical…this will provide more rigidity than laying the 2×6 flat.
  • Install the brace as close as possible to mid span of the truss.  The most deflection happens in the center of the span.
  • Secure the brace to each truss with two to three nails or screws.
  • Look for an open access area along the run of the truss to install the brace.  These are sometimes created to allow ductwork or plumbing to be installed and in some cases, they aren’t used or there is leftover space to add bracing.

I-Joists – Each manufactured I-joist supplier designs their floor systems separately.  So, it’s a good idea to contact them for instructions for repairing bouncy floors prior to starting.  One common method for stiffening up I-joists is to add plywood to the sides of the joists at mid-span by securing it to the top and bottom webs.  This plywood essentially strengthens the joists to help prevent deflections.

Dimensional Floors – The traditional 2×10 and 2×12 floor framing can be stiffened up by adding blocking between the joists at regular intervals.  Meaning, we can add short 2×10 pieces between the 2×10 joists to tie the adjacent members together.  Your access will be limited in some cases because of ductwork and plumbing, but there should still be plenty of open areas for installing the braces.  One other option for stiffening up joists from below is to add plywood to the bottom edge of the joists.  Again, this method can be limited somewhat do to the existence of mechanical systems.

Other Structural Problems

The explosion in the number of DIY projects over the past ten years, has brought inexperienced workers that can get people into trouble.  We’re not suggesting that people shouldn’t take on their own projects, we just want them to get good information before starting.  Removing structural walls in a home can be cause for floor deflections.  If the home was designed with an interior load bearing wall and it’s removed, the problem becomes much more severe than just excessive shaking when people walk across the room.  Removing a structural wall without replacing it with a properly sized beam designed by a professional, can lead to structural issues and possibly even structural failure.  If you suspect this might be your problem, be sure to consult an architect or engineer prior to repairing bouncy floors in your home.

Do have questions about your floor problem?  Let us know about it (  Check out these other Armchair Builder articles for more details on floor framing repairs…

Floors Squeak and Pop?  Tips for Repairing/Preventing

Home Defects from Framing Errors

RSS Feed