How Do You Tile Over Diagonal Plank Subfloor? (Explained)

Diagonal plank subfloors were the real deal a few decades ago. Therefore, if your home has such a floor, it’s probably vintage. If you plan on tiling over a diagonal plank subfloor, there are a couple of things that you have to know.

Wood diagonal plank

First, Is It Advisable to Tile Directly Over Diagonal Plank Subfloor?

It’s a recipe for disaster. Tiles are very picky when it comes to substrates. The project won’t last very long if you lay them on an old plank subfloor.

A plank subfloor is highly susceptible to humidity and temperature changes. That’s why it shrinks and swells on its own.

Also, plank subfloors aren’t very strong. There are tons of weak spots that can yield pressure when heavy loads are placed on top. Due to these reasons, when you tile directly over a diagonal plank subfloor, it will fail within a short duration.

How Do You Tile Over a Diagonal Plank Subfloor?

There are two ways you can tile over a diagonal plank subfloor. The first entails removing and replacing the subfloor with different materials such as concrete. This is quite time-consuming and expensive.

However, there is another method that is often used by tiling experts, which ensures the project lasts for a more extended period.

Step 1 – Gather Essential Materials

Tiling over a diagonal plank subfloor isn’t difficult. But certain materials are needed for you to complete this job successfully.

This includes screws, plywood, construction adhesive, thin-set mortar, a tile backer board, and finally, tiles of your choice.

Step 2 – Screw the Diagonal Plank Subfloor to the Joists

Before you can even do anything to a plank subfloor, you must ensure that it’s firmly held down. As mentioned earlier, such floors are usually very old.

Therefore, they must be screwed in to prevent them from loosening and coming off. Tiled prefer a solid surface that doesn’t move at all. This is a crucial step that shouldn’t be skipped.

Step 3 – Attach Plywood Over the Diagonal Plank Subfloor

The next step entails installing plywood over the plank subfloor. You may be wondering, why we need to add plywood. It makes the surface much stiffer and also promotes stability.

To ensure the floor isn’t too thick, you can install ½-inch plywood. It should be installed using construction adhesive. To be safe, screw it as well.

Step 4 – A Tile Backer Board Follows

Now that the floor is stiff and more stable, you can proceed to install a tile backer board. Even though one can tile over plywood, the ideal substrate for tiles is a special backer board. Add a backer board as you normally would on other tile installation jobs.

For those who have never worked with backer boards. Here is a quick guide, mix and apply thinset mortar to the plywood. Attach the tile backer board. Screw the board so that it firmly holds. Give it time to cure before proceeding to the next step.

Step 5 – Lay Tiles on the Backer Board

By now, you will have a suitable substrate for tile installation. Dust up the surface of the backer board, and apply some tile adhesive, followed by thinset.

Lay your first style according to the design you are interested in. You can retain the initial diagonal design used on the plank subfloor.

Or you can try something different. Do whatever works for you. Finish up by applying grout and let the tiles set before the room can be accessed.

Tiling over a diagonal plank subfloor may seem pretty hectic. But it’s better to follow the longer route and get it right than take shortcuts and end up with a failed project.

Will a Tile Backer Board Be Enough for Tiling Over Diagonal Plank Subfloor?

These are some of the shortcuts we were talking about. A tile backer board won’t be enough. You will still need to complement the floor with at least a half inch of plywood which should be laid using adhesive and screwed in.

Also, nearly all manufacturers of tile backer boards don’t recommend using their products on plank subfloors. If you go ahead and use the product against the manufacturer’s instruction, they will not compensate you when things go south.

If you are one of our regular readers, you are well aware that we are strict regarding adhering to manufacturer instructions.

Should I Hire an Expert Construction Worker to Tile Over Diagonal Plank Subfloor?

If you are a DIY enthusiast, it’s possible to perform this project yourself during the weekend or whenever you are free. Our guide above is pretty clear on how you should tile over a diagonal plank subfloor.

At the same time, we can’t dismiss the benefits of hiring an expert construction worker to tile over a diagonal plank floor. They will most likely use the process described above. You are also assured of a professional tiling project.

Let alone plank subfloors, tiling over old wood will most likely lead to performance issues. Therefore, it’s a good idea to bring in an expert who will assess the condition of the plank subfloor.

If it’s too old, they can recommend the removal of the structure. The only downside of hiring an expert is that you will spend more on labor fees.

Is a Kerdi Necessary When Tiling Over Diagonal Plank Subfloor?

That depends on where the tiles are being installed. If it’s a shower, kitchen, or any area that will be exposed to a lot of moisture, Kerdi matting is necessary.

The Kerdi role is to waterproof the surface. Tile backer boards have no problem when they are exposed to moisture, but a plank subfloor can get damaged by water.

Also, it can lead to mold growth. When tiling over a diagonal plank floor in an area such as a bathroom or kitchen, you can add one more step before laying tiles – installing a Kerdi matt. Kerdi isn’t the only waterproofing product.

You can use RedGard, DITRA, and many others. Research until you can find a strong waterproofing product.

Can You Tile Diagonally Over a Plank Subfloor?

Earlier, we talked about retaining the diagonal design of the plank subfloor. If you intend to use such a pattern because of its classic and elegant look, make sure that you follow all the above steps and then lay the tiles diagonally.

For this design, you will have to measure the area first to know how many tiles will fit in a row. Also, some tiles will have to be cut, especially those bordering the wall.

Having a diagonal tile pattern on the floor is more time-consuming. But it’s worth it, especially if this is a design that you find aesthetically pleasing. You will need to use tools such as a speed square for the corners.

Does the Condition of the Plank Subfloor Matter?

Inspection is the first thing you should do before tiling over a plank subfloor. Since this type of floor is common in older homes, there is a good chance that the wood may be in terrible shape.

Check for cracks, deflection, and swelling. Always fix the subfloor before installing plywood over it. Everything laid on top will be set if your subfloor is in excellent condition. Don’t forget to screw the old plank subfloor to the joists, so it’s securely held.

Won’t Using Plywood and Cement Board Make the Floor Too Thick?

Another concern you may have when installing tiles over a diagonal plunk subfloor is that the new floor can be too thick. This shouldn’t be a problem for most homeowners.

But if you are keen on the thickness, you can use a ¼-inch thick plywood and cement board. This will ensure that the new floor isn’t very thick.

As you attempt to minimize the thickness, you should remember that the stability of the flooring is crucial.

Is Replacing the Diagonal Plank Subfloor a Good Idea?

If the subfloor is very old or worn out, replacing it will be a great idea. A lot of homeowners shy at the idea of replacing a plank subfloor because it’s too much work, and you will spend a lot of money. But if it’s in terrible condition, that could lead to tile failure.

What can you replace the plank subfloor with? There are many options. A good example includes high-grade plywood.

If you have hired a professional contractor, you can ask for their expert advice about a suitable floor replacement. With a new and stronger subfloor, your tiles will adhere much more easily and last longer.

Will Tiles Crack When Installed Over a Diagonal Plank Subfloor?

When you install tiles directly over a diagonal plank subfloor, the tiles will crack or come off because of the movement on the floor. That’s precisely what will happen within a month or two.

To prevent project failure, you should add plywood, a tile backer board, and preferably an uncoupling membrane.

The latter helps in the absorption of movements that leads to the cracking of tiles. You don’t have to worry about tiles cracking if you get the installation right.

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