Is Your Subfloor Silent? This Old-School Trick Stops Squeaks

That relentless creak… That annoying squeak… It’s a sound every homeowner dreads, echoing through the house with every footstep. You’ve secured loose floorboards and tried superficial fixes, but the noise persists, emanating from deep within the structure of your floor. The culprit is often hidden, lying not in the beautiful hardwood you see, but in the layers of the subfloor beneath.

Many homeowners find themselves battling this invisible enemy, a problem often caused by friction between the layers of wood that make up your subfloor system. Before you resign yourself to a life of noisy floors or consider a costly, full-scale replacement, there’s a time-tested, surprisingly simple material that has been used for decades to solve this very problem: asphalt-saturated felt paper.

This humble material, often associated with roofing, holds a secret that seasoned builders have known for years. When placed strategically between layers of your subfloor, it can act as a crucial buffer, a slip sheet that isolates the wood panels and helps to silence the squeaks. But is it just about noise? This guide will delve into the dual role of felt paper, exploring how it also acts as a vital moisture retarder and how to use it correctly to build a floor that is not just quiet, but durable and protected for the long haul.

The Hidden War Under Your Feet: Why Subfloors Squeak and Fail

Before we can appreciate the solution, we must first understand the problem. A subfloor isn’t a single sheet of wood; it’s a structural system. Often, it consists of a primary layer of plywood or OSB (Oriented Strand Board) attached to the floor joists, and in many cases, a second layer of underlayment is added on top to create a perfectly smooth surface for the final flooring.

The noise you hear is the sound of wood rubbing against wood, or wood rubbing against fasteners like nails or staples. This movement, however minuscule, happens when there are slight shifts in the subfloor due to changes in humidity, settling of the house, or the simple act of walking across it. When two layers of wood are directly in contact, they can bind and release, creating that infamous squeak.

Friction and Moisture: The Two Core Enemies

Beyond the immediate annoyance of noise, there is a more insidious threat to your floor’s integrity: moisture. Moisture vapor can rise from a crawlspace or damp basement, slowly permeating the wooden subfloor. This can lead to swelling, warping, and even rot over time, causing not just squeaks but significant structural damage.

Many homeowners are surprised to learn that even new construction can have moisture issues. This is where the true, dual-purpose nature of installing felt paper comes into play. It addresses both critical issues—friction and moisture—simultaneously.

What is Felt Paper? More Than Just “Tar Paper”

Often called tar paper, the product used in flooring is technically asphalt-saturated felt. It’s a heavy-duty paper impregnated with asphalt, which gives it excellent water-resistant properties. While it’s a staple in roofing, its application in flooring has been a long-standing practice for very specific reasons.

It’s important not to confuse flooring-grade felt paper with roofing felt, as some roofing products can emit odors that are undesirable inside a home. Always ensure the product is intended for interior or flooring use. The felt serves two primary functions when placed between subfloor layers: it acts as a slip sheet to reduce squeaks and as a vapor retarder to manage moisture.

The “Slip Sheet” Secret to Silence

The core principle behind felt paper’s ability to reduce squeaks is simple: it creates a thin, stable barrier between the two layers of wood subfloor. Instead of wood grinding against wood, the top layer of plywood can now move ever so slightly on the smooth surface of the felt paper without creating friction-induced noise.

This doesn’t mean the top subfloor layer should be loose. It must still be securely fastened with screws and often glue. However, the felt paper accommodates the micro-movements caused by humidity changes and floor flex, preventing the materials from binding and creating noise.

A Breathable Moisture Barrier

A crucial distinction to understand is that asphalt felt is a vapor retarder, not a complete vapor barrier like a sheet of plastic. This is an important advantage when used over a wood subfloor. It slows the transmission of moisture vapor enough to protect the flooring, but it isn’t completely impermeable.

An impermeable barrier can sometimes be detrimental, as it can trap moisture within the subfloor, potentially leading to rot. Felt paper allows the subfloor assembly to “breathe,” letting trapped moisture slowly dissipate over time, which is much healthier for the wood structure.

Choosing Your Weapon: #15 vs. #30 Felt Paper

When you go to purchase felt paper, you’ll be met with two common options: #15 (or Type 1) and #30 (or Type 2). The numbers historically referred to the weight per 100 square feet. While modern manufacturing has made them lighter, the names have stuck, and they still represent two distinct thicknesses and levels of durability.

Making the right choice depends on your specific needs, the condition of your subfloor, and the type of flooring you plan to install. The differences are not just in weight but in permeability and tear resistance, making one a better choice over the other in certain situations.

Feature	#15 Felt Paper	#30 Felt Paper
Thickness & Weight	Thinner and lighter, easier to handle and cut.	Roughly twice as thick and heavy, more robust.
Durability	More prone to tearing during installation if not handled carefully.	Significantly more tear-resistant, holds up better to foot traffic.
Moisture Protection	Provides moderate vapor retarding. Suitable for most standard applications over wood subfloors.	Offers superior moisture resistance due to higher asphalt saturation. Better for areas with higher humidity concerns.
Best Use Case	Standard underlayment for nail-down hardwood floors over a stable, dry wood subfloor.	Between subfloor layers, over crawlspaces, or in areas where more robust moisture control is needed.
Cost	More economical and budget-friendly.	Higher initial cost but offers greater long-term protection.

For the specific task of layering between a primary subfloor and a top underlayment, #30 felt is often the superior choice. Its enhanced durability ensures it won’t tear as you install the second layer of plywood on top of it, and it provides that extra measure of moisture protection that is critical for the longevity of the entire floor system.

The Step-by-Step Guide to a Silent, Secure Subfloor

Proper installation is paramount. Simply laying down felt paper without the correct preparation and fastening techniques will not solve your problems and could even create new ones. Follow these steps meticulously for a professional result.

Step 1: Prepare the Primary Subfloor

Your work begins with the first layer of subfloor—the one attached to the joists. It must be clean, flat, and, most importantly, secure. This is your chance to eliminate any existing problems before you cover them up.

First, thoroughly sweep and vacuum the entire surface to remove all dust, dirt, and debris. Any stray particles left behind can create bumps or crunching sounds later. Next, perform a “squeak check.” Walk over every square foot of the subfloor and listen for noise. If you find a squeak, drive long deck screws through the subfloor into the floor joists below to pull the wood tight and eliminate movement.

Step 2: Roll Out and Overlap the Felt Paper

Begin along one wall, rolling out your first course of felt paper. Ensure the chalk lines, if present, are facing up as per the manufacturer’s instructions. Let the paper run a few inches up the wall; you will trim this later.

Overlapping the seams is critical for moisture control. Each subsequent row should overlap the previous one by at least 4 inches. This ensures there are no gaps where moisture vapor can penetrate. Use a utility knife for clean, straight cuts at the end of each row.

Step 3: Fasten the Felt Paper Securely

While the top layer of the subfloor will ultimately hold the felt in place, you need to secure it temporarily to prevent it from shifting while you work. Use a hammer tacker or a staple gun to fasten the felt to the subfloor. Don’t go overboard with staples; you only need enough to keep the paper flat and in position. A few staples every few feet along the seams and in the field is sufficient.

The goal is to prevent wrinkles and bubbles, which could interfere with laying the next layer of plywood flat. A smooth, taut installation of the felt paper is key.

Step 4: Install the Second Subfloor Layer

This is the most critical stage. The second layer of plywood or OSB provides the smooth, stable base for your finished flooring. Lay the sheets perpendicular to the direction of the first layer if possible, as this adds significant strength and rigidity to the entire floor system. Stagger the seams so they do not line up with the seams of the layer below.

Now, here is the secret to a truly rock-solid, squeak-free floor: use both adhesive and screws. Apply a serpentine bead of high-quality subfloor construction adhesive to the back of each plywood sheet before laying it down over the felt paper. Then, drive screws every 6 inches along the edges and every 8-12 inches in the middle of the sheet. The screws should be long enough to go through both layers of subfloor but not so long that they hit any wiring or plumbing below.

The combination of glue and screws creates a monolithic bond between the two subfloor layers, effectively making them a single, thick, and incredibly stable panel. The felt paper is now sandwiched in between, ready to do its job of preventing friction and retarding moisture.

Critical Mistakes That DIYers (And Even Pros) Make

Using felt paper seems straightforward, but a few common errors can undermine its effectiveness entirely.

• Relying on Felt to Fix Structural Issues: Felt paper is not a magical fix for a bouncy, unstable, or rotting subfloor. If your floor joists are spaced too far apart or your primary subfloor is too thin, you must address those structural problems first.

– Forgetting the Glue: Some installers skip the construction adhesive between the subfloor layers to save time or money. This is a huge mistake. The adhesive is just as important as the screws for creating a unified, silent floor.
– Improper Overlapping: Butting the seams of the felt paper together instead of overlapping them creates a direct path for moisture to travel through. An overlap of at least four inches is non-negotiable.

• Using the Wrong Product: Never use red rosin paper or other lightweight building papers as a substitute. They offer almost no moisture resistance and can break down over time. And be wary of old flooring materials; some older paper backing can contain asbestos, a serious health hazard. If you suspect you have older layers, understanding the risks associated with asbestos paper backing is crucial.

Felt Paper vs. Modern Alternatives: What’s the Best Choice?

In the world of flooring, technology is always advancing. Today, you’ll find a wide array of synthetic underlayments, foam pads, and rubberized membranes, all promising superior performance. So, is old-fashioned felt paper still relevant?

The answer is a resounding yes, particularly for its use between subfloor layers. Many modern underlayments are designed to go directly under the finished floor (like laminate or vinyl plank) to provide cushioning and sound absorption. However, for the specific job of creating a slip plane and vapor retarder between structural wood panels, asphalt felt remains an excellent, cost-effective, and time-proven solution.

Synthetic underlayments are often more durable and can be completely waterproof, but they are also more expensive and, like plastic sheeting, can potentially trap moisture if not used in the right application. For a nail-down hardwood floor installation over a double-layer wood subfloor, felt paper is still considered a best practice by many seasoned installers.

Your Flooring Type Matters: Special Considerations

The benefits of a properly constructed subfloor extend to every type of flooring. A solid, silent base ensures your finished floor looks and performs its best for years to come.

For those considering modern floating floors, the subfloor preparation is just as critical. When you’re thinking about installing floating vinyl plank over OSB, a double-layer subfloor with felt paper provides an exceptionally flat and stable foundation, preventing the planks from separating or flexing. Similarly, a strong subfloor can help protect your investment in premium materials and make future repairs easier. If you ever need to know how to fix dents in engineered wood floors, you’ll be glad you have a solid base that prevents further damage.

The Final Verdict: Is Felt Paper the Secret Your Subfloor Needs?

That persistent squeak is more than just a nuisance; it’s a sign that the components of your floor are not working in harmony. By adding a layer of asphalt-saturated felt paper between your subfloor layers, you are addressing the two primary causes of flooring failure: friction and moisture.

It is not a cure-all for major structural flaws, but when used as part of a properly executed subfloor system—complete with adequate fastening and adhesive—it is an incredibly effective tool. It is the professional’s secret to building a floor that feels solid, remains silent, and stands the test of time.

The next time you walk across your floor, listen closely. If you hear the tell-tale creaks and groans of a floor in distress, remember this old-school trick. A simple roll of felt paper, installed with care and precision, might just be the key to achieving the silent, solid floor you’ve always wanted.