Beneath the Bounce: What Makes Floors Vibrate and How to Fix It (Part 2)

So, if you’re reading this blog, you probably already read part 1 where we discussed the basics of floor vibrations and are now looking for solutions. That’s great! In this part, we’ll explore common methods to address bouncing and vibrating floors in both existing homes and new constructions. Let’s get started!

How to Address Floor Vibrations in As-Built Homes

If you are experiencing floor vibrations in your existing home, several effective methods can help mitigate this issue. Here’s a comprehensive guide, organized from the most to least effective strategies:

1. Adding a Support Beam or Wall

Installing a support beam or load-bearing wall beneath the vibrating area to reduce deflection.
Position the beam perpendicular to the joists at the midpoint of their span. Ensure proper sizing and support to handle the additional load. This method significantly enhances floor stability by redistributing weight, reducing the frequency and amplitude of vibrations. See the calculated difference by adding a support.

2. Add Bridging or Blocking

Installing bridging or blocking between joists to distribute loads and increase stiffness.
Use solid wood bridging and install at intervals no greater than 8 feet along the joist span. Secure them tightly to prevent movement and improve load distribution. This method enhances damping by increasing the continuity of the floor system.

3. Subfloor Upgrades

Reinforcing the subfloor by securing it more firmly to the joists or adding an additional layer of plywood.
Use construction adhesive and appropriate screws instead of nails to secure the subfloor. This increases holding power and minimizes the risk of floor squeaks. Adding a layer of at least 1/2" plywood, with joints staggered and screwed every 12 inches along joists, can further reduce vibrations by increasing stiffness. Increasing subfloor thickness to 7/8" or even 1-1/8" can significantly enhance assembly stiffness, reducing vibration frequency.

4. Doubling Joists

Adding additional joists alongside the existing ones to increase floor stiffness.
Use adhesive and mechanical fasteners to attach the new joists. Ensure they run the full length of the span. This method can effectively reduce vibrations by increasing the overall rigidity of the floor system. The added stiffness helps lower the amplitude of vibrations, making them less noticeable.

Downside? There’s a strong chance electrical, plumbing, and ducts have been installed through the floor system, which will prevent the installation of additional joists. Though this may be one of the most effective methods for reducing vibrations, I’ve listed it near the bottom due to impracticallity. See the calculated difference by doubling a joist.

5. Install a Floating Floor

A floating floor system can help isolate and dampen vibrations by decoupling the floor covering from the subfloor.
Use high-quality underlayment designed for vibration reduction. Ensure proper installation to avoid gaps and movement, which can enhance the overall effectiveness of this method. Floating floors and their underlayment can improve damping.

Preventing Floor Vibrations in New Home Construction

For those building a new home, y’all are the lucky ones. Proactive measures during the design and construction phases can prevent floor vibrations, and design techniques from both the section above and below can be selected. Here are the key strategies, organized from most to least effective:

1. Choose Deeper Floor Joists

Using deeper joists can significantly improve floor stiffness and reduce vibrations.
Opt for joists which offer a higher stiffness-to-weight ratio. For instance, a 9-1/2” deep joist will pale in comparison to a 16” deep joist. The depth increases ‘basic stiffness’, which helps in lowering both the frequency and amplitude of floor vibrations. See the calculated differences by increasing joist depth.

2. Optimize Joist Spacing

Reducing the spacing between joists decreases the span and increases floor stiffness.
Though joist spacing of 16” on-center is still common, spacings of 19.2” to 24” on-center are now just as common. Closer joist spacing improves load distribution and stiffness. Consistent spacing and proper alignment are crucial for maximizing this benefit. See the calculated differences by decreasing joist spacing.

3. Use Thicker Floor Sheathing

Thicker sheathing adds rigidity and reduces vibrations.
Use 7/8" or 1-1/8" plywood or OSB, glued and screwed to the joists. This method creates a strong bond and reduces movement, thereby enhancing the floor’s transverse rigidity and minimizing vibrations.

4. Implement Vibration Rating Systems

Utilize vibration rating systems to design floors with minimal vibrations.
Rating systems assess deflection limits and vibration performance to guide the selection of joists and spacing that meet comfort criteria. These systems optimize stiffness and vibration control. These vibration formulae—based on research and empirical studies—considers load distribution, material properties, and structural dynamics to predict floor performance and minimize vibrations. Typically, the higher the numerical rating, the better the floor performance.

BCI® and Weyerhaeuser provide valuable vibration metrics and performance data, offering builders reliable options for addressing floor vibration. It is advisable to consult with your engineer or architect.

5. Enhanced Design Practices

Advanced design concepts such as composite action between joists and subfloor can improve floor performance.
Ensure the subfloor is glued and screwed to the joists, creating a composite structure that acts as a single unit. Additionally, proper attachment of transverse partitions (walls spanning perpendicular to the joists) can significantly enhance floor performance by increasing the amount of floor bracing.

6. Continuous Spans Vs. Simple Spans

Spanning joists continuously over multiple supports improve vibration control compared to a series of simple spans.
Continuous joists that span multiple supports generally improve floor performance by increasing stiffness and reducing deflection. This design helps minimize resonance and vibrations, leading to a quieter and more stable floor. However, be mindful that continuous joists extending into adjacent spaces can also transmit vibration and sound through the floor assembly. See calculated differences between simple vs. multi span.

Why It Matters?

Addressing floor vibrations is crucial for ensuring the comfort and satisfaction of your home environment. Working with a qualified professional to implement these strategies can lead to a quieter, more stable living space, whether you are enhancing an existing structure or planning a new build. By understanding and applying these methods, you can significantly improve the performance and satisfaction of your flooring system.

For expert advice and thorough inspections, consider consulting with Kurtz Residential, LLC. Our home inspection services can help identify any floor vibration issues, giving you the information needed to address them effectively with an engineer or general contractor. Book a service today to ensure your home meets the highest standards of comfort and quality.