Repairing wood subfloor typically requires cutting flooring

Q: My upstairs toilet once had a leak that damaged the floor around the base. The area around the toilet became soft and discolored, and a friend recommended that I have someone familiar with mold look at it. The mold guys came and cut out an area around my toilet and left me with a big hole in the floor. I had vinyl in the bath, but with the water damage, it had to be removed. My biggest concern is how to replace the wood subfloor around the toilet. How do I do it?

A: We did a job like yours, but it had a little twist. We showed up at a client’s house and went upstairs to see the damage. We gave the lady an estimate, then went to work removing the toilet and vinyl, and then cutting out the damaged subfloor.

We were in and out of the house, running to get parts throughout the course of the day. At the end of the day, the floor was sealed up and the bath back to normal, and so we went downstairs to collect a check, which the woman happily handed over.

Right then, she asked if we had seen her cat, and we told her we didn’t even know she had one. The woman said that she could hear the cat, but she couldn’t find him. Uh oh.

Apparently, while we were on one of the trips out of the house, the cat got curious and decided to jump down into the hole we had cut. He found himself in the space between the ceiling of the first floor and the floor of the second floor. I think the cat was having a good time until we removed a can light to bring him back to reality. So, the lesson here is to keep curious pets away from holes in your floor.

Depending on how the subfloor was cut out, you may have access to the joists so you can nail the new subfloor patch to them. Typically though, you will have to cut back the flooring to expose the joist’s surface, and you can do this with a circular saw.

Set the blade depth so that it is barely over the thickness of the subfloor, and watch out for nails or they will ruin your blade. Cut so that the finished area has 90-degree corners so that fitting the patch will be easier; you want to cut so that there is a nailing surface for each edge of the subfloor. In fact, you may have to add a thickness of lumber to the existing joist.

Use 16d nails and thicken the joists, if necessary. You can then cut new subfloor material and set it in place.

By the way, take a careful measurement of the thickness of the subfloor. The floor must be exactly even or you will have problems. If you have a scrap of plywood that is 1/16th of an inch off, don’t use it. Instead, go buy the correct thickness.

Since the damage is around your toilet, you are left with the toilet’s drainpipe sticking up out of the hole. On the top of the drainpipe is the flange that gets screwed to the subfloor.

You will have to fit the subfloor patch into place in two pieces, cutting out a small radius for the pipe to fit through. You want to leave enough wood, however, so that the flange has enough support to rest on.

Remember, this area will have a lot of weight to support, so make sure the area has plenty of “meat” under the subfloor to support it. Once you fit the subfloor under the toilet flange, screw the flange to the subfloor and make sure the floor does not flex when you stand on it.

Now you can consider what flooring you will lay down. If you are going to use vinyl, make sure there are no seams or differences in height, as the vinyl will show every imperfection in the subfloor (you will have to use leveling compound).

Ceramic tile will be more forgiving because you will have to install the backer board to stiffen up the floor even more. If you choose tile, remember that when you reinstall the toilet the distance from the toilet mounting flange to the toilet base will increase dramatically, so you will have to use a thicker wax ring or double up on them.

Mike Klimek is a licensed contractor and owner of Las Vegas Handyman. Questions may be sent by email to handymanoflasvegas@msn.com. Or, mail to 4710 W. Dewey Drive, No. 100, Las Vegas, NV 89118. His web address is www.handymanoflasvegas.com.