How To Replace Damaged Subfloor Decking

Currently, I have damaged subfloor decking in two of my investment properties. As you can imagine this is a subject that is on my mind. As a result, I decided to write a post about it. Ripping up and replacing the floor of your home seems like a daunting task, but it’s not difficult at all. You can remove and replace damaged subfloor decking in just a few hours with your run of the mill tools.

A Tale of Two Properties

I’ll give you a little back story on the two properties. The first of is a waterfront house on the Jersey Shore. The second, an old farmhouse, I bought as a flip.

The Jersey Shore House

I bought this house in 2016 and lived there for three years, while I was in the Army. It’s a beautiful house on the water, which for someone who likes boating and fishing is perfect. I kept it as a rental property when I transferred to NY. Finding tenants to live there was not a problem. Fast forward three years, my tenants lease ended, and they moved out. I started doing a few repairs and touch ups to get it ready for the next round.

The Discovery

I was about finished when I checked out the crawlspace and discovered I had a water leak. There was wet insulation, wet subfloor decking and who knows what else going on. I’ve been through water damage more than once and I assure you it can get really ugly really quick. I contacted my insurance company to start a claim at this point.

I found the source of the leak after a lot of searching and guessing. It turned out to be a pinhole leak in the supply line for the refrigerator. Along with finding the leak, I identified damage to the drywall behind the refrigerator and baseboards. Fortunately, my insurance company rocks and already assigned a contractor to assess the damage, mitigate the water damage, and repair it. Currently repairs are underway. All I have to do is monitor progress and occasionally prod the contractor doing the work.

Thank Goodness For Insurance

You’re probably wondering what insurance company provides this kind of service. USAA does. Not all insurance companies are as user friendly and proactive. If you’re eligible to become a USAA member I highly recommend it. Before you ask, no I’m not getting anything for making a plug for them. I just think they’re a terrific company who takes care of their members and families.

The Farmhouse

I bought the farmhouse after I retired from the Army and became a full-time real estate investor. I’m not exaggerating when I house needed A LOT of work. It had been vacant for nearly ten years and in that time had deteriorated significantly. As pulled up the old floor tile in the kitchen I wasn’t surprised to find a section of the decking was rotted. Honestly, I’m amazed I didn’t fall through it. You can imagine my relief that it was a small area that needed repair and would be easy to complete.

Let’s Build

As I said replacing damaged subfloor decking may sound like a major project but it’s not as tough as it sounds. First let’s discuss what you’ll need for the project.

Materials: Your shopping list will be pretty short. You’ll need 3/4 inch thick plywood or 5/8 inch thick OSB, and 1 1/2 to 2 inch long #8 wood screws. I prefer to use plywood, but OSB will do the job and often costs less than plywood. How much you’ll need will depend on how much subfloor you’re replacing.

Tools: From start to finish you’ll need several tools which are typically part of any novice DIY’ers took kit.

• Circular Saw
• Table Saw (Optional)
• Wreaking Bar
• Hammer or Nail Puller
• Power Drill
• Impact Driver
• Tape Measure
• Straight Edge

Once you have all your materials and tools gathered, you’re ready to start getting to work.

Remove the Damaged Subfloor Decking

The first step is to remove the damaged decking. The condition of the damaged decking and how it’s attached to the floor joists will affect how you removed it.

The decking was severely degraded in my project, and it was attached with nails. I was actually able to make a hole in it by stomping my foot. Yes, it was that bad. I removed it using a wreaking bar and some muscle power to rip it up from the joists.

If the damaged subfloor decking isn’t severely degraded, you can remove it in entire sheets or sections. I recommend cutting it into sections with a circular saw. You’ll need to set to cut at the appropriate depth across the sheet of plywood or OSB. If the subfloor is attached to the joists with nails use a wreaking bar to pry it up. Subfloor attached with screws, remove them and pull up the damaged sheet.

Once you’ve removed the damaged subfloor inspect floor joists for signs of damage and remove any remaining screws or nails. If you find the joists are good to go, you’re ready to move on. If you see signs of damage those floor joists will have to be replaced or sistered. To sister the joist attach a 2×6 to the damaged joist and beams to strengthen it. This provides a surface to attach the decking to.

Cut the Decking

The next step in this project is measuring the opening in the subfloor and cut the new decking to fit. If you’re lucky a single 4’x8′ sheet that you can plop right down in that hole. How often does that happen? haha. If not, you’ll have to measure the size of your opening and determine how much decking you’ll need. Be sure to consider where the decking will land on the floor joists. The decking must land at least on center (OC) of the joist in the middle of the floor for support. If it’s along the wall it can overlap the entire width of the joist.

In my case my opening measured 4′ 4″ x 8′. So close to being easy, but so yet so far. This was further complicated by the joys of working on a farmhouse that was built in 1850. The spacing between floor joist was 20″ vs. today’s standard 16″. The long edge of the plywood hung over the third floor joist by 4″ and short of the rim joist. I solved this problem by cutting two sheets of plywood to 52″ inches long spanning the full width of the hole.

After you’ve determined the length or width you need to cut the decking begin by measuring and marking the decking in several spots then mark a line across as your cut line.

Make Your Cut

To cut the decking to size, there are a few options available to you depending on what tools you have. Using a table saw to rip the plywood provides the straightest and most precise cuts. Now, unless you’re doing a lot of this type of work, I don’t recommend buying one. Using a good circular saw is your next best option.

When using a circular saw, place the decking on sawhorses or use a couple of 2×4 or 4×4 to elevate and support the decking while you cut.

Line the saw up with the cut line. Keep the blade just to the waste side of the line and begin cutting. It goes without saying to try to keep as straight as possible as you cut. It will take some practice to get good at this. Now that you’ve cut your decking to size, you’re ready to install it.

Install the New Decking

You’ve cut the decking to size. Now place it and get ready to attach it with screws or nails. Slide the decking into place and check that it fits flush with the adjacent decking and fits the hole properly.

Attaching the decking is a pretty simple task. You can use nails or screws to do this. I prefer screws, since it provides a firmer connection and makes future removal just a little easier. I recommend using an impact driver to drive in the screws in just below the surface of the decking. That said any power drill with a diver bit will work.

Start by driving one screw in at a corner of the decking. Continue down the length of the decking along the floor joist, spaced at 8 inches apart. Repeat this action along each floor joist until the new decking is firmly attached in place.

Wrapping it Up

Congratulations you’ve successfully replaced your damaged subfloor decking! As you saw, it may seem like a major repair, but it’s really not difficult for you to do yourself. It will save you a lot of money you would spend on a contractor. I hope I’ve given you the confidence to tackle this or a similar project now or in the future. All that’s left is figure out what type of floor you’re going to lay on top of it. That’s another project.

Happy Building!