What to put under tongue and groove flooring?

Author: Vergie Waelchi II  |  Last update: Monday, June 15, 2026

If you're installing your tongue and groove flooring onto a concrete floor, an underlayment is necessary to prevent moisture from accumulating between the concrete and the flooring.

Does tongue and groove flooring need underlayment?

Do Tongue-and-Groove Floors Need Underlayment? While you may be able to avoid using underlayment, it is preferable to do so in the long run. Underlayment diminishes floor noises, functions as a moisture barrier, and evens the area on which the flooring is laid.

Do you need to put anything under hardwood flooring?

When it comes to new flooring installation, it pays to invest in a quality underlayment for your hardwood floors. Wood is a beautiful product, but it requires extra support to provide the best outcome for residents of homes, apartments, office buildings, and more.

What do you put between a hardwood floor and a subfloor?

You want self-leveling underlayment. It's a type of concrete designed for use over wood subfloors. Make sure to read the directions so you know how to seal the seams in your floor before you put it on.

How do you secure tongue and groove flooring?

Use a flooring nailer to secure boards through the tongue at a 45-degree angle. Nailing at this angle ensures that the nails are hidden and the boards are tightly connected. Tap boards into place with a rubber mallet before nailing. This ensures a snug fit between the boards.

How To Install Tongue and Groove Flooring | Ask This Old House

Should tongue and groove flooring be glued?

When it comes to learning how to lay Tongue & Groove flooring, there are a few different techniques. It can either be floated, nailed or glued down. The floating method makes the most of this style of installation, as it doesn't require nails or adhesives.

What are the disadvantages of tongue and groove flooring?

Cons. If the tongue and groove system isn't held together properly, such as using too little glue, boards can separate over time. It's important to use a sufficient amount to keep your flooring looking pristine for longer!

What is the best underlayment for hardwood floors on wood subfloor?

What is the Best Underlayment for Hardwood Floors? Felt is used as underlayment for hardwood floors. It forms a hard surface without making the planks wet, which can cause them to warp. Cork is also a good choice, as it resists moisture and supports heavy loads on wood.

Can I put flooring directly on subfloor?

Most modern vinyl flooring, such as Happy Feet, comes with an attached underlayment or pad, often with a moisture barrier built-in – unless the pad is cork. If the product you choose doesn't have an attached underlayment, you can almost always install directly over the subfloor without one.

Why put paper under hardwood flooring?

But it's still commonly used and if you speak with builders or wood flooring installers or architects, you hear all sorts of reasons for the purpose of this paper: It prevents floor squeaks. It's a vapor barrier. It cuts down on dust.

What goes down before wood flooring?

Use an underlayment or moisture barrier to cover the floor before adding the hardwood. These offer benefits including sound dampening and protection against spills.

What is the best moisture barrier for hardwood floors?

Here are some common types of moisture barriers for flooring:
  • Polyethylene sheeting: This is a popular and cost-effective vapor barrier. ...
  • Bitumen-coated kraft paper: Often used under hardwood flooring, bitumen-coated kraft paper is another reliable vapor barrier.

Do you have to put something under flooring?

Underlayment's great, but if you're lucky enough to have a dry climate, spotless subfloors, and little need for noise control, it isn't a necessity. If you have all the optimal conditions and don't want to spend the extra money for additional benefits, you might as well just lay down your laminate without it.

Does anything go under hardwood floors?

One of the most popular types of hardwood underlayment is felt. This option provides basic moisture resistance and sound absorption. You can choose heavier layers of black felt for additional insulation, sound absorption, and moisture resistance.

Is tongue and groove better for subfloor?

Tongue and groove plywood offers several benefits over standard plywood sheets, making it a preferred choice for many contractors and DIY enthusiasts for subfloors, roofing and wall sheathing.

Do tongue and groove floorboards have to be joined on top of a joist?

Tongue and groove joins do not need to end on a joist but all square edges should be fully supported. Secure subsequent boards by applying Mega Strength PU Adhesive along all sides of the T&G before inserting the next board.

What happens if you don't put a moisture barrier under vinyl flooring?

When moisture penetrates your flooring, it can cause mold, mildew, and the potential for water damage. A moisture barrier helps control the water vapor's movement to help protect your floors. Therefore, if you're installing floors in an area that sees moisture, even a little, a vapor barrier is needed.

What goes between subfloor and wood floor?

You have the top layer that is your floor covering (Hardwood, Laminate, Vinyl, Carpet, etc.), next you have the underlayment (usually a thin layer of fiber, foam, rubber), below that you have your subfloor (plywood, OSB, concrete), and lastly you have the joists which are the foundation to your floors.

What is the best flooring for bad subfloor?

For very uneven flooring, laminate sheets or tiles may be a better bet. This material is more flexible, but may reveal the imperfections in the surface. The most durable and attractive option for an uneven floor is often a pour on option, such as epoxy.

Can you lay hardwood directly on subfloor?

Most engineered flooring can be installed using staples, full spread adhesive or a floating method over an approved subfloor. Make sure you have a sturdy subfloor: 3/4-inch CDX plywood is preferred and 3/4-inch OSB is acceptable.

What can I use as underlayment?

Foam, cork, and rubber are common soft underlayments.

Should you use a vapor barrier on a wood subfloor?

Yes. Hardwood flooring is quite sensitive to moisture and it's always worth adding a moisture barrier during installation.

Is tongue and groove outdated?

For many uses, tongue and groove boards have been rendered obsolete by the introduction of plywood and later composite wood boards, but the method is still used in higher-quality boards.

How thick should tongue and groove flooring be?

Working with 3⁄4″ stock, that plays out to a 1⁄4″-thick by 1⁄4″-long tongue, and a matching groove. A longer tongue (one that's 1⁄2″ long for example) is prone to break at the shoulder.

Can you screw down tongue and groove flooring?

Tongue-Tite is a specialist screw designed for softwood, hardwood and fibre tongue & groove floorboards. With the Tri-Lock™ TS threadform the screw will drive straight through the boards & into the substrate without pre-drilling.

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