Tongue and groove siding is one of the oldest siding styles still commonly used today. Tongue and groove siding pieces interlock together along their edge, greatly reducing the number of fasteners required.

In most cases, tongue and groove siding is made from naturally rot-resistant materials such as cedar, redwood, and pressure-treated lumber. Tongue and groove siding is relatively easy to install and does a good job (with regular maintenance) of protecting the structure.

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Today, tongue and groove siding is still in use in certain home designs, such as a cabin or country-style home. Tongue and groove siding can be used indoors, or outdoors and can be installed vertically, or horizontally, depending on the application. This makes tongue and groove siding versatile and popular with do-it-yourself enthusiasts.

Tongue and groove siding can also be installed with simple carpentry tools most DIYers will have. Today, we will discuss the common installation techniques used by the pros and offer a couple of “Pro Tips” to make the project simple and rewarding.

What Is Tongue and Groove Siding and Why Would You Want It

Tongue and groove siding initially gained popularity during the industrial age where machinery made milling wood very fast and consistent. This is important with tongue and groove siding because each piece connects to the other mechanically. By reducing the number of fasteners required, the siding is more durable as well as more attractive. 

Each piece, or “stick” as it is referred to by the pros, has a groove along one long side and a corresponding tongue on the other. These interlocking edges prevent the siding from bowing and twisting, as each stick keeps the adjoining stick straight and flat. This not only greatly reduces the number of fasteners required, but also makes sealing the siding easier. In contrast, sealing other wooden siding designs such as board and batten, can be much more involved due to the irregularities of the material.

How Long Does it Take to Install Tongue and Groove Siding?

Professionals can generally install a square (100 square feet) of tongue and groove siding in about 4-6 hours, but some designs take longer. A typical installation installs the sticks vertically such as board and batten style siding, but tongue and groove siding can be installed horizontally, similar in appearance to logs. Tongue and groove siding is best installed in a team of two or three installers for maximum efficiency. 

Tongue and groove siding is not particularly complicated to install, but care must be taken to follow the process carefully. This makes the project popular among do-it-yourselfers with carpentry skills. 

It should be noted, however, that a mistake made early in the project can be very time-consuming and expensive to correct, so it is critical for new installers to minimize mistakes. Not keeping the correct side facing out and not checking for plumb are among the most common.

How Much Does Tongue and Groove Siding Cost?

Most tongue and groove siding materials cost between 2.00-6.00 per square foot installed. This can vary widely however, as in most cases the siding is made from natural materials. Location can affect the price of a commodity such as wood, as can the type and style of siding. Traditionally, southern U.S. states will have the lowest cost, while northern states tend to be more expensive.

How to Get Started Installing Tongue and Groove Siding

To begin a tongue and groove siding installation, the first step is to measure how much siding the project will require. Will the siding cover the entire wall structure or perhaps just enough for accenting around stone? Once you know how much you need, the next step is to decide the details, like the profile shape and the wood species available. 

The best way to estimate the materials needed is to measure the approximate width and height of the area to be sided and multiply them together. For example, let’s say we are siding a wall that is about 96” (8’) x 120” (10’). If we multiply these measurements, we get approximately 80 square feet. In siding terms, one “square” is 100 square feet. Tongue and groove siding is often available in one or two square boxes.

To understand the options available, it may help to familiarize yourself with a few common styles of siding. Tongue and groove siding is often sold as a flat board, with a chamfered edge on all four long sides (or at least the side facing out). This chamfer is just a 45 degree bevel milled into the wood from the factory. This helps reduce splinters and results in a more prominent groove. Many tongue and groove siding materials have both a smooth side and a rough side, allowing the installer to install either for appearance. This is especially common in cedar and poplar tongue and groove siding. When you have your style and material selected, it’s time to lay out the project and get started.

Pro Tip. Professional installers must be sure to install the correct side facing outward, as correcting mistakes later can be extremely difficult and costly. The pros will also select certain boards to go with other boards to improve the appearance.

Step 1. Prepare the Surface

Tongue and groove siding has the advantage of strength, rigidity, and thickness. As such, vertically installed tongue and groove siding can often be installed directly over T1-11, drywall (as interior paneling), oriented strand board (OSB) or plywood. Tongue and groove siding installed horizontally can sometimes even be installed directly over wall studs, but very accurate nailing is required. Generally speaking, as long as the surface has a minimum of ⅝” sheathing, tongue and groove siding will work well. However, the thicker the sheathing the better. If the structure has house wrap, it should be inspected and repaired if necessary. If it does not, it is strongly recommended to install it before beginning any siding installation.

Step 2. Laying Out the Area

The professionals will often begin a project by setting up their work area. In most cases, there will be one person who makes cuts and notches, while two others do the measuring and install the material.

By the way, it is a good idea to purchase an extra box of siding from the same lot, as these will likely have come from the same logs. Having an extra box is handy when sticks break or must be trimmed to fit. 

As mentioned previously, tongue and groove siding can often be installed over existing surfaces. However, in some cases, furring strips may be required. These furring strips are often just narrow scraps of wood that are nailed perpendicularly to the wall studs, ensuring a solid nail surface. These furring strips are also necessary if tongue and groove siding is being installed over non-wood surfaces such as cement block, stucco, or brick.

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In a normal installation, the first step is to make a level line at the bottom of the wall everywhere the siding will be installed on the house. This level line is then squared to the nearest vertical corner of the wall. This establishes a plumb line, or perfectly vertical line. This plumb line will represent the location of the outside corners (if the project will use them), and will also be perfectly square (90 degrees) to the level line. This is because the corners will establish the frame and overall appearance of the job, so it needs to be accurate. 

The level line is usually made with a chalk line, and represents the location of the bottom of each stick. If the level line and plumb line are referenced perfectly, each stick can simply be nailed along the level line and inserted into the next stick of siding. For those new to vertical siding installation, it is a great idea to plumb each stick as it is installed. It only takes a second and will indicate any issues before they become difficult to correct.

Let’s use the example from earlier and say the wall is 120” (10’) wide. Since we’re using the first stick to establish a perfectly vertical line, it is critical not to compound any errors. For example, if the first stick is a couple of degrees out of plumb it may not be noticeable. However, if the next stick is also a couple of degrees out of plumb, then the next stick will be four degrees out of plumb, and so on. Since the material is often only 6” wide, that means there will be at least 20 sticks over a 120” (10’) span. Doing the math, it becomes obvious that the last few sticks will be noticeably tilted. In most cases, trying to correct the issue over just a few sticks can make the installation look amateurish.  

Step 3. Attaching the Siding 

To begin, the groove side of the stick is placed up against a corner or corner board. Never start with the tongue side, because it will cause a gap the same width as the tongue, which will then need to be covered. 

Pro Tip. On the first stick, it is more important that it be installed perfectly plumb than tightly up against a corner. It is possible the house and corner might have settled and may no longer be plumb. 

Sticks up to 6” wide or so can usually be installed with a single face nail at the top and bottom. Each stick is then nailed as closely as possible to the grooved side with the intention of nailing through the tongue of the preceding stick as well. This usually offers the most attractive method, however in most cases finish nails must be used. They must be large enough (usually #8 or larger, depending on the material) to penetrate the sheathing by at least 1 ½”. These fasteners must also be hot-dipped galvanized, as zinc-coated fasteners are not recommended. To reduce the chance of splitting the wood, pilot holes can be drilled in advance.

In situations where this method is not practical, ring shank or twist nails are often approved. These nails must also be #8 or larger (depending on the wood) and hot-dipped galvanized. In some brands, the box may simply say “siding nails”. These nails are usually face nailed about 16” apart along the groove side.

The process is repeated until the last stick meets an obstacle, such as a door or corner. Often the last stick must be trimmed to width. This can be done with essentially any saw, but the professionals will usually use a circular saw. In most cases, this last stick will stop at the end of the wall, and the next stick on the adjacent corner will overlap its edge. This keeps the corners square and stable, allowing the outside trim (if there is any) to do the same.

Step 4. Installing the Second Course (if needed)

Tongue and groove siding usually comes in sticks long enough to cover one story, but of course, some homes have two or more. In these situations, another product should be installed between the vertical courses. This product, usually called drip edge, is typically made from either galvanized metal or aluminum.

Professionals will have a large machine called a brake that forms the drip edge into a crisp, straight shape. For do-it-yourselfers without this tool, roll flashing can also be used. In most cases, the drip edge is installed underneath the second course and overlaps the first.

To install the drip edge, it is nailed to the sheathing approximately two inches above the first course using hot-dipped galvanized roofing tacks. The large head on the roofing tack prevents the drip edge from tearing away from the tack. The drip edge then overlaps the first course by 1” to 2”, but is not attached to the first course. 

Step 5. Installing the Remaining Courses

Next, the second course can be installed just like the first. In some designs, the detail will require an additional trim board to cover the joint and drip edge. Although not usually required, this trim board helps delineate one story from another, while providing additional protection for the joint. This trim board is often just a stick of siding with both the tongue and grooved side cut away. These trim boards can be any size that accents the appearance of the siding. The trim board is usually installed using the same fasteners as the siding. Because the board is often narrow these nails should stay away from the edges by at least an inch to prevent splitting. 

Pro Tip. Unlike horizontal lap siding, vertical tongue and groove siding courses can be installed directly over each other. Tongue and groove siding does not require offsetting joints to prevent water infiltration.

Step 6. Applying the Finish

Tongue and groove siding is very versatile and as mentioned earlier, also used indoors. The vertical siding used indoors is often a high-grade natural wood such as cedar or poplar and is stained or sealed with a wood sealer. When the product is used as exterior siding, much more consideration must be given to the finish.

Although the manufacturer’s instructions should always be closely followed, as a rule, the siding should be sealed with exterior grade polyurethane, paint, or any other weather-resistant finish. In this case, more is more, so the professionals will often seal the surface at least twice with a high-quality paint or sealer. Since this will represent the vast majority of the maintenance required, it is recommended not to scrimp. 

Is Tongue and Groove Siding For Me?

If you love the look of vertical siding, tongue and groove offer the visual appeal of wood, relatively simple installation, and durability. Tongue and groove siding has remained much the same since its introduction, explaining its longevity. Tongue and groove siding is affordable and can be installed with a few simple tools, making it a worthwhile DIY project. For those homeowners not scared away by regular maintenance, tongue and groove siding can be a worthwhile investment.

Editorial Contributors
Matt Greenfield

Matt Greenfield

Matt Greenfield is an experienced writer specializing in home improvement topics. He has a passion for educating and empowering homeowners to make informed decisions about their properties. Matt's writing focuses on a range of topics, including windows, flooring, HVAC, and construction materials. With a background in construction and home renovation, Matt is well-versed in the latest trends and techniques in the industry. His articles offer practical advice and expert insights that help readers tackle their home improvement projects with confidence. Whether you're a DIY enthusiast or a seasoned professional, Matt's writing is sure to provide valuable guidance and inspiration.

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