Continuous span floors have benefits of being able to span longer compared to simple span floors with the same joist section.  This does not come without cost: continuous span joists transfer vibration from one floor to the other along joist length.  In contrast simple span joist floors contain vibration within the loaded floor and effect on other parts of the structure is minimal.

There are many misconceptions on how to remedy continuous joist floor problems like: 1) Putting blocking or squash blocks at intermediate bearing.  This will not change vibration mode of the floors at all; the only benefit will be a better stabilization/holding of the joist at intermediate bearings, 2) Cutting top flange ( and web ) at the intermediate bearing, this will change vibration mode of the floors by preventing vibration transfer between the floors, but it will also increase vibration problems on both floors since simple span has higher deflection for the same load compared to the continuous span.  In addition to this, cutting the flange will invalidate floor design since the top flange at intermediate support is critical for joist moment capacity and this must not be done and 3) Added ceiling will help but to a lesser degree since added mass always reduces floor performance to a degree.

The best way to deal with continuous joist floor vibration problem is to reduce initial deflection under “footstep impact load” so that transfered vibration to the other floor is also reduced accordingly.

Engineered IBS 2000 bridging has been repeatedly proven to reduce deflection by 50+%, thus radically reducing vibration effect of footstep load.

Thus, continuous span vibration problems can never be totally eliminated; but with the installation of IBS 2000, they can be greatly reduced bringing floors to acceptable levels.

Luxor has recently posted a demonstration video showing the different performance between some common floor bridging products (blocking and conventional bridging) and IBS2000. Each one of the three test setups was subjected to a 450lb load (such as a common footstep load).

As seen in the video, IBS2000 delivered more than 5 times the performance of the nearest competitor! You can trust IBS2000 to fix any problem you might have with a bouncy floor.

Click here to view the video on You Tube.

“I have ceramic tiles on my floors and I actually had grout cracks in some of the floor areas.  We filled in the grout and in a few weeks, the grout cracked again.  Will the IBS 2000 help eliminate any future grout cracks?” 

Two things that you must look at: 1) are the joists deflecting or sagging a lot and 2) is there excessive vibration or bounce in the joists.  If you find that the joists are deflecting too much, then you must first lift or jack up the joists.  Then you can install the IBS 2000 bridging.  Luxor recommends that you use retrofit IBS units.  The IBS 2000 will structurally lock the joists together, stiffening up the floor system.  This will minimize joist movement. 

Please note that grout crack could have been caused by poor installation ( tile/mortar bed or floor system ), inadequate design ( was a wider o/c spacing used or a heavier dead load ) or subfloor issues ( excessive deflection of subfloor between joists ).

We have had many calls from homeowners complaining about bouncy or shaky floors that cause annoying vibration, rattling china, cracking grout and so on.

Over the years traditional remedies have been used to resolve the problem and stiffen the floor. One of the biggest issues is not just the cost to fix the floor, but how effective the floor performance (how the floor feels) would be afterwards.

This article shows that the simplest and most cost effective way of fixing bouncy floors is by using Luxor’s patented IBS engineered bridging and doing the floor analysis with Luxor’s Floor Performance Rating (FPR) system. The FPR is based on point load deflection (this is what occurs when one steps on a floor while walking across the room) and predicts floor performance.

For our comparison we will use a 16 foot by 20 foot room built with 16 foot floor joists. We will analyze six test cases using the five traditional remedies that have been used to fix bouncy floors as well as IBS Engineered Bridging:

1. Add bridging or blocking
2. Double-up floor joists
3. Add another layer of subfloor
4. Add a ceilling
5. Add a beam
6. Use IBS Engineered Bridging

1 - ADD BRIDGING OR BLOCKING

The simplest solution most people use is to add conventional bridging or blocking between the joists. They can buy the product readily and they can do it themselves.

After installation, in most cases, they will realize that the floor feels the same as there was no noticeable difference.

Pros:

• Easy and relatively fast to install.
• Lowest cost.

Cons:

• If blocks are used, they must be cut to precise lengths.
• Blocks must be toe-nailed.
• The tops of the cross bridging could be rubbing the underside of the subfloor.
• Has to be installed from underneath.
• The least effective solution.

Floor Performance: Floor will feel 1 to 4% better.
Cost: $100 or $.31 per square foot

2 - DOUBLE UP FLOOR JOISTS

Usually, a friend or designer might suggest doubling the floor joists. Now, we have a double joist which should act like a beam. “The floor should feel a lot better.”
The labour cost is high since all the wires, pipes, etc. have to be removed and then put back. Now, another joist has to be fastened to the existing one. It is very difficult to put in a fixed 16 foot piece of joist into a space that is 16 feet in length with a space of 12” or 16”.

Pros:

• Will achieve a better performing floor.

Cons:

• Labour intensive
• Have to take out pipes, wires, HVAC lines, etc.
• Difficult to put joists onto bearing walls.
• Have to put back new pipes, wires, HVAC lines, etc.
• Have to buy joists for each space.
• Has to be installed from underneath.

Floor Performance: Floor will feel 38% better.
Cost: $600 or $1.90 per square foot

3 - ADD ANOTHER LAYER OF SUBFLOOR

Sometimes, a person might recommend that another subfloor layer be put down on top of the existing one. The theory is that this will make the subfloor stiffer, which will lead to less bounce.

A problem with this is that, in most cases, there is already an existing floor covering such as ceramic, vinyl or hardwood. If this is the case, another remedy is needed.

Pros:

• Will achieve a better performing floor.

Cons:

• Very labour intensive.
• Can only be done if there is no floor covering or carpet.

Floor Performance: Floor will feel 34% better.
Cost: $650 or $2 per square foot

4 - ADD A CEILING

A common remedy is to strap the whole underside of the joists and then add drywall. People think that this will tie all the joists together.

Pros:

• Will achieve a slightly better floor.

Cons:

• Labour intensive.
• Expensive material cost, strapping and drywall.
• Can only be installed from underneath.
• In relation to cost versus floor performance, it is the worst case.

Floor Performance: Floor will feel 11% better.
Cost: $1,000 or $3 per square foot

5 - ADD A BEAM

Usually, the last remedy is to put in a beam. Associated with the beam will be columns and footings. Even though the floor will feel so much better, a lot of people do not want to use this remedy, since the room will now be divided.

Pros:

• Will achieve the best performing floor.

Cons:

• High labour and material cost.
• One or more posts will be needed with footings.
• The depth of the beam affects headroom.
• The room will now be divided eliminating the open concept.
• Requires a contractor and maybe a structural engineer.

Floor Performance: Floor will feel 150 to 220% better.
Cost: $850 or $2.65 per square foot

6 - USE IBS ENGINEERED BRIDGING

Install a row of IBS at midspan. Either use standard or retrofit IBS units.

If needed, two rows of IBS can be added. The cost will be slightly more and the floor performance will be better. ( an extra $100 for a 77% better floor ).

Pros:

• Easy and fast to install.
• Standard or retrofit units available.
• Can install around existing pipes, wires, HVAC lines, etc.
• Easy for a Do It Yourself installation.
• Will achieve the second best performing floor.
• Overall, the best solution, cost to floor performance.

Cons:

• Has to be installed from underneath.

Floor Performance: Floor will feel 45% better.
Cost: $300 or $.94 per square foot

SUMMARY:

The simplest and most cost effective solution to eliminate a bouncy or shaky floor is to use a row of the IBS. Any handyman can install the IBS without altering or changing the actual floor system. There is no need to “guesstimate” labour and materials. Luxor’s FPR will predict how the floor will feel.