Easily add an extra layer of plywood over your subfloor with these tips!

My mother wanted to redo her bathroom with some new floating laminate flooring. To save on installation costs, I promised I’d remove the tile for her. How hard could it be, right? I found that it was easiest to demolish the tile and then was left with thinset on the plywood subfloor. After looking for DIY solutions online, I found a grinder to remove the thinset. Long story short, I chewed up her floor.

The only thing we could do was replace the subfloor, right? Well, I read that it’s a simple process to lay down an additional layer of plywood, provided that the structural integrity of the original subfloor was intact. It was quite easy to install an additional layer of plywood, but there are some questions and facts that need to be considered when doing it yourself.

Easily add an extra layer of plywood over your subfloorPin

In this article, I want to talk about the easiest ways to remove old flooring from a subfloor before adding a new layer of plywood. I also want to explain the difference between the two types of plywood that you can add to your subfloor: underlayment and regular plywood. Finally, I’ll let you know how I installed the new layer of underlayment for my mother’s bathroom!

Step 1: Remove Old Flooring

It may seem obvious, but the first step to adding a second layer to your subfloor is to remove the old flooring. The most popular flooring you’ll find is tile, carpet, wood, and laminate. As technology and home improvement grow, you never know what you’ll come across, but these are the most common ones you’ll want to know how to remove. In any instance, you’ll want to first remove the floorboards to make removal of the flooring and installation of new plywood easier.

Carpet

If you’re lucky, you’ll be removing carpeting. Personally, I love carpeting. But home renovation is more often moving away from carpet because of the allergens, hair, dirt, and stink it collects (though, I say this is only if it’s not taken care of).

Carpet is, by far, the easiest flooring to remove. Simply use a utility knife to cut the carpet into manageable-sized strips. Pull it out from the nails along the wall, and slowly roll it up across the room. As you remove the strips, you’ll find soft foam insulation beneath them. Do the same with this. After these have been removed, you’ll want to use plyers to pick up any staples that may remain behind in the subfloor and a crowbar to remove the tack strips.

Wood

Wood is usually connected to the subfloor with glue and nails. Sometimes, you’ll find it is connected with one of these or both. The simplest way to remove wood is to first figure out the lengths of the wood planks. These vary in size, so you should cut these down with a circular saw to make the pieces more manageable. Of course, be sure to set your saw to the thickness of the flooring so you do not cut the subfloor!

To lift the wood, use a sledgehammer and a crowbar. Simply tackle each piece slowly to lift the wood from the floor. Once you get the hang of it, you’ll buzz through this process, but watch out for loose nails as you move along the floor. Also, you’ll want to go slower if you plan to donate or sell the reclaimed wood.

The nails or staples left behind will need removing next. Use a nail claw and pliers to lift all nails and staples. To get rid of the glue, use a chisel and hammer or an adhesive remover and scrape up the gunk. Sweep up all debris and then use a shop vac to get the last bit of dust.

Tile

Tile is one of the harder items to remove from plywood subflooring. The reason for this is because when it is properly installed, the tile will have been back buttered with thinset. This is a cement and sand adhesive that is spread on the back of the tile and the base of the floor to create a strong bond. When done correctly, this will be so strong you will have a difficult time lifting it. This is good, because who wants loose tiles when you’re happy with the flooring?

It’s not worth the energy and time it would take to gently pry up each tile with a chisel, so your best bet is to go at the tile with a sledgehammer. Breaking up the pieces of tile will break the bond. Be very careful, because pieces can fly, and they are sharp. Always use safety gear and goggles when doing this.

Once the tile is up, there will be a lot of thinset left behind on the subfloor. To remove this, you have a few methods, which are all fairly exhaustive but essential to prevent uneven flooring. You can either use hot water and vinegar to wet the thinset down. Once it has sat for a bit, it can be scraped up fairly easily. You can also use a hammer drill with a large chisel attachment. The power of the vibrations from this power tool lifts the thinset from the subfloor. Be sure to sweep and vacuum up all dust and pieces.

Laminate

The final flooring option we’ll look at is laminate. Laminate and tile can contain asbestos if it was installed before 1980. If you’re unsure when yours was installed, seek a professional for help. If you know this was installed after the 80s, you can continue on your own.

Modern laminate tends to be tongue and groove, which only requires a crowbar and some patience. You’ll want to wiggle out the first set of boards from the wall, and then the rest will pop out pretty easily. You’ll also want to get rid of the foam underlayment that cushioned the laminate.

If you have cheaper or older laminate (also called vinyl) to deal with, this is likely peel-and-stick laminate. Similar to carpet and wood, if you cut this, you’ll find it easier to remove and dispose of. Use a utility knife to make strips or squares. Strips work well if it is one large piece because the weight will help to pull it off as you roll it up.

If you’re able to remove the left behind glue as you roll up the vinyl, do this with a 5-in-1 tool or scraper. If not, use a long-handled scraper to lift the glue. You can also use a heat gun with a scraper to loosen the adhesive and lift it. Again, be sure to vacuum up any debris.

Step 2: Remove Underlayment

The next step to laying a second subfloor layer is to check for underlayment. You may have come across this while you were removing the flooring in the previous step. Underlayment is a thin piece of material – usually foam, plywood, or cement board – that provides additional support for the type of flooring you’ll install.

Some DIYers and contractors call the underlayment the subfloor, but this is not the same. The subfloor is the thicker piece of plywood that lays directly on top of the floor joists.

When you remove the flooring, you may find an older underlayment, which can be discarded. This is often quite handy for those floors that have glue and thinset attached to it. You do not need this in place when adding a second layer of plywood to the subfloor. The underlayment may be attached by glue, which will require you to put in some elbow grease to remove. Modern construction usually leaves it floating, though. Depending on the type of flooring you will be installing, the manufacturer may suggest a specific type of underlayment, which you will want to install after laying the second layer of plywood.

Step 3: Decide on Plywood

There are many reasons why you may want to add a layer of plywood to your subfloor. First off, you need to keep in mind that the subfloor is the structural integrity of the floor. This is what you will walk on, set your furniture on, and keep yourself from falling between the joists. Here you must decide, are you adding a second layer of thin plywood as an underlayment or the second layer of subfloor? This will affect the thickness of the plywood you select.

As mentioned before, underlayment is a thinner piece of plywood that is about ¼ thick. Subflooring runs thicker since it provides structural support – usually ¾ inch to 7/8 inch. No matter which you choose, your installation process will be the same. You should just be aware that what you install will change the height of your floor, so be aware of this for doors or alternate flooring in another room (it could cause uneven floors).

Step 4: Acclimate Plywood

Now you’re ready to install the new underlayment or subfloor. First, be sure that the floor is completely clean from all nails, screws, glue, staples, carpet fibers, dust, and thinset. The best suggestion for this is to use a shop vac because you can use it for both wet and dry materials. Some people suggest running a long magnetic strip over the floor to lift any metals, like nails and staples, so they won’t damage the shop fac. However, if you’ve already swept, this won’t be as much of an issue.

Now that the floor is dust- and debris-free, be sure to acclimate the wood. I recommend bringing in the plywood before you even lift the original flooring, if possible. As long as your home does not have both a greenhouse room and a walk-in freezer, the environment should be the same throughout. So bringing the wood into an adjacent room for 72 hours should be as good as having it in the actual room. This way, you can work while the wood acclimates. Of course, if you prefer to keep the wood in the same room that it will be installed, that’s your choice.

Step 5: Install Plywood

To install the plywood, you’ll simply lay the sheets down and nail them in place. Many DIYers suggest placing the sheets perpendicular to the current subfloor. This will increase the strength of the subfloor. If you’re installing underlayment, you’ll want to follow this same method. This also ensures that the seams never line up, which could cause a weak spot.

If possible, make sure the seams of the plywood meet at floor joints. When you nail these in place, it’ll guarantee extra support. As you lay each plywood sheet down, use galvanized screws or shank nails to fasten the two plywood floors together.

Shank nails have divots over the body to provide extra grip within the fibers of the wood. Galvanized screws will provide an even better grip than the nails and are rust-resistant. Some DIYers choose to use a staple gun because it is a faster process, and that is okay, too. Just be sure to space the staples closer to each other than the six inches you would space the nails or screws (staples should be about two inches apart).

As you lay each sheet, be aware of the fit. These pieces should sit next to each other with no resistance. Remember, wood swells with the seasons, so you wouldn’t want to cause buckling and bowing in your flooring. If you can leave up to 1/8-inch space between the sheets, these can be sealed with a silicone sealant before laying down your new flooring. If the sheets rub together, use a saw to trim the edge of the plywood board. Just remember, measure twice and only cut once!

Step 6: Keep in Mind

One more thing before we’re done: keep in mind that every flooring manufacturer will suggest a type of underlayment to complement their product best. It’s up to you if you choose to follow their advice, but it’s always the best option. Also, remember that plywood is not water-resistant. If you intend to lay down a product that can allow for seepage, you’ll either want a different underlayment or you’ll want to provide a water barrier product that will protect your subfloor from moisture and eventual rot (like I did in my mother’s bathroom.)

 

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