Using Plastic Shims for Flooring (6 Install Tips)

Ever dreamt of transforming your space with beautiful new floors?

I know I have, countless times!

But let’s be real, that dream can quickly turn into a nightmare when you discover your subfloor is about as level as a rollercoaster.

Uneven subfloors are the bane of any flooring installer’s existence, whether you’re a seasoned pro or a weekend warrior.

You’ve got your perfect flooring picked out, ready to go, but then BAM!

You notice the first few planks are rocking, or that tile doesn’t quite sit right.

That’s where our unsung heroes come in: plastic shims.

These little guys are like the secret sauce to a flawless flooring install.

But using them correctly?

That’s the key.

In this article, I’m going to share my years of experience and knowledge, diving into the world of plastic shims.

I’ll give you six essential tips that will help you tackle that uneven subfloor head-on and achieve a floor you’ll be proud to walk on!

Section 1: Understanding Plastic Shims

What are Plastic Shims?

Plastic shims are thin, often wedge-shaped pieces of plastic used to fill gaps, level surfaces, and provide support.

Think of them as tiny adjustable feet for your flooring.

They come in various shapes, sizes, and thicknesses, allowing for precise adjustments.

Materials and Types:

Materials: Typically made from high-density polyethylene (HDPE) or polypropylene (PP), these plastics are durable, moisture-resistant, and won’t rot or splinter like wood.
Types:
- Wedge Shims: Tapered for fine adjustments.
- Horseshoe Shims: U-shaped for spacing and leveling.
- Rectangular Shims: For general leveling and support.
- Adjustable Shims: Stackable and interlocking for customized heights.

Why Plastic Over Wood?

I’ve used both wood and plastic shims over the years, and trust me, plastic is the way to go for flooring.

Here’s why:

Moisture Resistance: Wood can warp, rot, and attract mold in damp environments. Plastic is impervious to moisture.

Consistency: Plastic shims are manufactured to precise dimensions, ensuring consistent thickness and performance. Wood can vary in thickness and density.
Durability: Plastic shims won’t compress or degrade over time like wood can.
No Splinters: Say goodbye to painful splinters!

Why Leveling Matters: The Shim’s Role

A level and properly supported floor is crucial for several reasons:

Aesthetics: An uneven floor is visually unappealing and can make furniture look crooked.
Structural Integrity: Unevenness can cause stress on flooring materials, leading to cracks, warping, and premature wear.

Safety: An uneven floor can be a tripping hazard.
Warranty: Many flooring manufacturers require a level subfloor for warranty coverage.

Plastic shims are the key to achieving this level surface.

They fill in low spots and provide a stable base for your flooring, preventing movement and ensuring a long-lasting, beautiful result.

Flooring Materials and Shims

Plastic shims are versatile and can be used with a wide range of flooring materials:

Hardwood: Shims prevent squeaks and ensure a solid, level surface for nailing or gluing.

Laminate: Shims eliminate rocking and provide a stable base for the interlocking planks.
Tile: Shims prevent cracking and ensure a level surface for even grout lines.
Vinyl Plank/Tile: Similar to laminate, shims provide stability and prevent movement.

Engineered Wood: Shims address subfloor imperfections to ensure proper installation and prevent future issues.

Section 2: Preparing for the Installation

Tools and Materials

Alright, let’s get down to brass tacks.

Here’s what you’ll need to tackle this project like a pro:

Plastic Shims: A variety of sizes and thicknesses. I recommend having an assortment on hand.
Level: A 4-foot level is ideal for most flooring projects. A shorter level can be helpful for tight spaces.
Straight Edge: A long, straight piece of wood or metal to detect dips and humps in the subfloor.

Measuring Tape: For accurate measurements.
Pencil: For marking shim locations.
Construction Adhesive (Optional): For securing shims in place.

Screws or Nails (Optional): For additional security, especially in high-traffic areas.
Hammer or Drill (If using fasteners):
Safety Glasses: Always protect your eyes!

Dust Mask: Protect yourself from dust and debris.
Vacuum Cleaner: For cleaning the subfloor.
Self-Leveling Compound (Optional): For addressing major subfloor imperfections (more on this later).

Assessing the Subfloor

This is where the rubber meets the road.

Before you even think about laying down flooring, you need to thoroughly assess your subfloor.

Why is this important?

Because a flawed foundation will lead to a flawed finished product.

Here’s how to do it:

Visual Inspection: Look for obvious signs of damage, such as cracks, water stains, or mold.

Level Test: Place your level on the subfloor in various locations and directions. Note any areas where the bubble isn’t centered.
Straight Edge Test: Place your straight edge on the subfloor and look for gaps underneath. This will reveal dips and humps.
Sound Test: Tap on the subfloor with a hammer. A hollow sound can indicate a void or delamination.

Measuring for Success:

Use your measuring tape to determine the depth of any low spots. This will help you choose the appropriate shim thickness.
Mark the locations of high and low spots with your pencil.

Take photos or create a sketch of the subfloor, noting the areas that need attention.

Important Note: If you find major subfloor imperfections (e.g., large cracks, significant unevenness), you may need to use a self-leveling compound before installing shims.

Choosing the Right Shims

Not all shims are created equal.

Here’s how to choose the right ones for your project:

Flooring Material: Consider the thickness and flexibility of your flooring material. Thicker materials may require thicker shims.
Subfloor Condition: If you have minor imperfections, wedge shims may be sufficient. For larger gaps, you may need rectangular or adjustable shims.

Load-Bearing Requirements: In high-traffic areas or under heavy furniture, use thicker, more durable shims.
Moisture Levels: If you’re installing flooring in a damp environment (e.g., bathroom), choose moisture-resistant shims.

I usually keep a variety of shims on hand.

It’s better to have too many than to run out in the middle of the job.

Section 3: Top 6 Install Tips for Using Plastic Shims

Okay, now for the good stuff!

Here are my top six tips for using plastic shims like a seasoned pro:

1. Start with a Clean Slate

You wouldn’t build a house on a pile of dirt, would you?

The same principle applies to flooring.

A clean subfloor is essential for proper adhesion and a long-lasting installation.

Here’s how to prep your subfloor:

Remove Existing Flooring: If you’re replacing old flooring, remove it completely.
Remove Debris: Sweep, vacuum, and scrape away any dirt, dust, nails, staples, or adhesive residue.

Address Moisture: Check for signs of moisture and address any leaks or dampness before proceeding. Use a moisture meter to ensure the subfloor is within the acceptable range for your flooring material.
Clean the Surface: Use a damp cloth or mop to clean the subfloor. Allow it to dry completely before installing shims.

2. Measure Twice, Shim Once

This old adage is especially true when it comes to flooring.

Accurate measurements are crucial for proper shim placement and a level floor.

Identifying High and Low Spots:

Use your level and straight edge to identify areas where the subfloor is uneven.

Mark the locations of high and low spots with your pencil.
Use your measuring tape to determine the depth of any low spots.

Precise Shim Placement:

Start with the Lowest Spots: Begin by shimming the lowest areas of the subfloor to bring them up to the level of the surrounding surface.
Position Shims Strategically: Place shims close to the edges of the flooring material and under areas that will bear weight (e.g., under furniture legs).
Cut Shims to Size: If necessary, use a utility knife or scissors to trim shims to the appropriate size.

3. Gradual Layering for Stability

Don’t try to fix everything with one massive shim.

Instead, use a gradual layering technique to build up the low spots.

Why is this important?

Stability: Multiple thin shims are more stable than one thick shim.
Adjustability: Layering allows for fine-tuning and adjustments as you progress with the installation.
Prevent Shifting: Gradual layering reduces the risk of shims shifting or compressing over time.

Pros and Cons:

Multiple Shims:
- Pros: More stable, adjustable, less likely to shift.
- Cons: Can be more time-consuming.
- Single, Thicker Shim:
- Pros: Faster installation.
- Cons: Less stable, less adjustable, more likely to shift.

I personally prefer using multiple thinner shims whenever possible.

The extra time is worth it for the added stability and peace of mind.

4. Secure the Shims

Once you’ve positioned your shims, it’s important to secure them in place to prevent movement during flooring installation.

Adhesive vs. Fasteners:

Adhesive: Construction adhesive is a good option for securing shims to the subfloor, especially when installing floating floors (e.g., laminate, vinyl plank).

Fasteners: Screws or nails can be used to secure shims to wood subfloors, especially in high-traffic areas or under heavy furniture.

Best Practices:

Adhesive: Apply a small amount of construction adhesive to the back of the shim and press it firmly into place.

Fasteners: Use screws or nails that are long enough to penetrate the subfloor but not so long that they protrude through the flooring.
Placement: Space fasteners evenly across the shim.

Important Note: If you’re using adhesive, make sure it’s compatible with your flooring material and subfloor.

5. Test for Leveling Throughout the Process

Don’t wait until the end to check for levelness.

Test as you go!

Methods for Checking Levelness:

Level: Use your level to check for levelness in various locations and directions.
Straight Edge: Use your straight edge to check for dips and humps between shims.
Tapping: Gently tap on the flooring material with a rubber mallet. A hollow sound can indicate an uneven surface.

Frequency:

Check for levelness after installing each row of flooring.
Pay special attention to areas where you’ve used shims.

Tools for Accuracy:

Laser Level: A laser level can be helpful for large areas or complex installations.
Digital Level: A digital level provides precise measurements and can be useful for detecting subtle unevenness.

6. Final Inspection and Adjustment

You’re almost there!

Once the flooring is installed, it’s time for a final inspection.

Look for:

Uneven seams
Rocking or movement
Gaps under the flooring

Hollow sounds

Making Adjustments:

If you find any issues, carefully remove the affected flooring material and adjust the shims as needed.

Use a utility knife to trim any shims that are protruding.
Replace the flooring material and check for levelness again.

Section 4: Common Mistakes to Avoid with Plastic Shims

Even with the best intentions, it’s easy to make mistakes when using plastic shims.

Here are some common pitfalls to avoid:

Improper Placement: Placing shims in the wrong locations can actually worsen the problem.
Over-Reliance on a Single Shim: Using one thick shim instead of multiple thinner shims can create an unstable surface.

Neglecting to Check for Level: Failing to check for levelness throughout the process can result in a floor that is still uneven.
Using the Wrong Type of Shim: Using shims that are too thin or too thick can compromise the stability of the floor.
Failing to Secure Shims: Not securing shims in place can allow them to shift during flooring installation.

Ignoring Major Subfloor Imperfections: Attempting to fix major subfloor issues with shims alone is a recipe for disaster.

Anecdote:

I once worked on a project where the homeowner tried to install laminate flooring without properly addressing the uneven subfloor.

They used a few shims here and there, but didn’t bother to check for levelness.

The result?

A floor that was not only uneven but also squeaky and prone to movement.

They ended up having to tear out the entire floor and start over.

Don’t let this happen to you!

Section 5: Conclusion

Plastic shims are an indispensable tool for any flooring installer.

They allow you to create a level, stable surface, ensuring a beautiful and long-lasting floor.

By following the six essential tips outlined in this article, you can confidently tackle any uneven subfloor and achieve professional-quality results.

So, embrace the challenge, grab your shims, and get ready to transform your space!

Call to Action:

I’d love to hear about your experiences with flooring installations and how plastic shims have made a difference in your projects.

Share your stories, ask questions, and share your own tips in the comments section below.

Let’s build a community of DIY enthusiasts and flooring experts!

Using Plastic Shims for Flooring (6 Install Tips)