How to Remove and Replace a Rotten Subfloor

I'm B Cody and I'm Ashley .

Whether you're remodeling your entire home or just sprucing up a room with a fresh coat of paint , we're gonna show you how to do it right .

This house is in pretty good shape , but there's one project that we have to tackle before we get to anything else .

Look at this floor , it's terrible and we need to replace it , but it's not as scary as it looks .

I promise .

There are two common ways to build a house .

The first is called slab on grade .

A mold is built out of wood .

All of the sewer and water lines are laid out within the mold reinforcement wire is added and then the mold is filled with concrete .

The second method is to build a house with a crawl space or basement .

This house has a crawl space and sits about two ft off the ground on concrete blocks .

The floor joist rests on top of the blocks .

Plywood is then added to the top of the joy to create the sub floor .

Some flooring can come in several materials .

You have particle board , OS B board , untreated plywood or untreated tongue and groove plywood before we repair anything .

We need to figure out why this floor rotted in the first place .

The flooring rots due to moisture but where did the moisture come from ?

Maybe there's a leak or something that was fixed in the past that we don't know about if this damage was caused by a leaky water line .

We'd probably find more rot near the kitchen sink or dishwasher .

The floor isn't rotten under the window so we can rule out a leaky window and the attic spaces look dry .

There aren't any signs of rotten wood up there .

I'm pretty sure the moisture is coming from the ground .

The lot that this house is on is a little low .

So I'm thinking that underneath the house it holds a little moisture all the time .

Yeah .

The summers here in Florida get really hot .

So I bet that moisture is evaporating up into the subfloor .

I totally agree .

But some good news is the two by eight floor joists are in great shape .

I didn't see any signs of wood rot when I was crawling around down there ?

That's great .

But how are we going to minimize the amount of moisture in the crawl space ?

Well , for starters , we can install a crawl space fan to increase air flow and reduce the moisture down there .

Right now .

The water runs off of the roof to the ground directly next to the foundation by adding gutters and down spouts .

We'll be able to direct the water away from the house .

We can also install a vapor barrier underneath the house .

It's a plastic sheet which blocks moisture from collecting under the subfloor and the floor jots .

All of these little fixes are really going to help us with our moisture problem .

But now it's time to get to work on the actual rotten floor .

There's two ways that we can repair this floor .

We could patch the existing hole with plywood , but getting the new subfloor to match up perfectly with the old subfloor is not something we want to tackle .

So what we're going to do is take out these cabinets and completely demo these kitchen floors , which means we're going to be starting from scratch , but that's a great thing .

It will ensure that our floors are completely leveled .

There's a lot of tools we could use to cut out the subfloor .

In this case , we're going to be using a circular saw before you start any demo .

Be sure you're wearing your safety gear .

We've identified where the plumbing and electrical lines will be , but to be on the safe side , we're going to take it slow .

We're going to cut back the subfloor in a section at a time , use the pry bar to remove the subfloor and pull out any nails we find and inspect the next section for plumbing and electrical .

I started the demo by removing the rotten plywood .

This stuff was so brittle .

All I had to do was let the weight of my sledge hammer do the work .

This part of the demo didn't even feel like work .

It was actually a lot of fun .

The tedious part was removing all of the nails from the floor .

Joy .

I don't know of a quick way to do this .

You just have to rip the nails out one by one .

The last thing we wanna do is cut into the floor joist .

So what we're gonna do is measure the thickness of the sub flooring and adjust our blade depth to match .

Be sure to keep your hands out of the way of the blade .

While you're adjusting the depth , cutting up the floor into small squares , makes ripping them up and carrying them into the trash a lot easier .

But this process still took a long time .

Some parts of the floor actually had two layers of plywood to cut through and pry up and I took it slow because cutting my leg on a rusty nail or having an accident with the circular saw wouldn't make Ashley very happy .

After I cut out all of the subfloor , I used a reciprocating saw to clean up the edges of the flooring near the walls and to get rid of the rotten subfloor beneath the hardwood .

I removed several pieces of it to expose the rotten wood .

Then I set the blade depth of the circular salt to match the depth of the hardwoods and subfloor .

So I wouldn't cut into the floor joys .

Then I used the existing edge of the hardwood as a guide to clean up the edge .

After a little bit more demo of the rotten wood , we are ready for the next step .

Now , we have a huge hole in the floor .

We need to cover .

We'll start by measuring the area to figure out how much plywood we're going to need .

You can measure with a standard tape measure or use a laser tool like this looks like we have approximately 250 square feet to cover .

Plywood comes in four ft by eight ft sheets .

So I'm thinking eight pieces should work , but we can't just lay down plywood .

We want to attach each side of the plywood to the substructure of the house .

We need to add boards in between the floor joints to screw the new subfloor into .

We're going to use two by six pressure treated lumber like this .

We also want to make sure all the floor and joys are level .

If they're not level , we'll either shim in pieces of lumber or add boards to level the floors looks like the floor is a level .

So it's finally time to lay down the sub flooring to prevent the floor from squeaking when you walk on it .

We're going to add a beat of glue to each joy .

So the plywood subfloor doesn't separate later .

I like to use two inch exterior deck screws on projects like this with a cordless impact driver .

It's important to leave a 18 inch gap between each sheet to allow the wood to naturally expand during the seasons .

We started out by laying down as many full size sheets of plywood as we could .

It felt really good to cover up almost half of the floor without cutting a single piece of plywood .

Well , we can't fit any more full sheets of plywood into this space .

So we're going to have to start cutting pieces to fit into the spaces .

It's kind of like one giant puzzle piece by piece .

We applied the measurements from the floor to the uncut .

Plywood struck lines with a chalk box and use this circular salt to make the cuts after adding more glue to the floor joy , we dropped in the plywood and screwed it all down .

See , that wasn't so scary , but it was a huge project .

It was and that's something to consider when doing home renovations like this .

And there's no shame in hiring a professional to do the work .

But if Diy is how you roll now , you know how to do it , right ?

Hey , guys , thanks so much for watching this video .

Be sure to hit the like button and let us know in the comments .

Any questions that you have , if you want to try out any of the tools we use in this video , we left the links in the description below , as well as some links to additional articles to help you out with other foreign projects .

And if you want to see more of our how to videos hit that subscribe button and stay tuned to the lowe's youtube channel .