How to Install a Toilet Flange on a Wooden Floor

Installing a new toilet can be considerable work. But, installing a flange on a wooden floor is actually easy. Just make sure you have a flange that’s right for your toilet and you’re good to go. 

The toilet flange should always sit on the finished floor. So, if you only have the subfloor in, you’ll want to install the flange loosely, about ¼ of an inch above the subfloor. And, of course, if you’re putting in a new floor, you’ll have to cut the pipe access first. Otherwise, there’s very little to it. 

How to Install a Toilet Flange on a Wooden Floor

Installing a new toilet is a relatively simple process, providing you’ve got the plumbing in place. In this article, we’re going to cover how to install a toilet flange on a wooden floor, when you already have the sewage lines in place. 

What You’ll Need: 

  • Closet flange matching your sewage pipe (three- or four-inch flange) 
  • Pipe glue 
  • Drainpipe 
  • Screws (Wood screws, usually 1½ inch in length). Most wood screws use a flat head, but you’re more likely to have an easier time if you buy Philips screws. Make sure you get wood screws, which don’t feature course threading up to the head. If you choose screws with threading to the head, the screw could split the wood. 
  • Box knife 
  • Sandpaper or sanding pad 
  • Disposable gloves
  • Optional: Chalk, measuring tape, power drill, Forstner or spade bits, jigsaw, tape measure 

Optional: Cut the hole for the flange 

If you haven’t cut the hole for your flange, you’ll have to do so. That normally means lining up the sewage pipe with where the toilet should enter the floor, based on where you want the toilet. This is called roughing in your toilet. 

  1. Place the toilet where you’d like it on the floor. Here, you want 10-14 inches between the base of the toilet and the wall. This leaves room for the toilet tank. In addition, if you have a wall-mounted toilet, you want the wall to be at least 10 inches thick to accommodate the tank. 
  2. Use chalk or a pencil to trace around the toilet.
  3. Remove the toilet and measure the distance from the toilet to the drain inside the toilet on the underside. Measure these out inside your toilet outline. 
  4. Double check to make sure you’re not positioning the drain over a joist.
  5. Trace a small section of your plumbing pipe to make the hole round. If you have the option, use Schedule 40 pipe in a 3-inch format. 
  6. Use a power drill with a spade or Forstner bit to start a hole on one side of the pipe hole. Go through the floor and the sub-floor until you hit open space.
  7. Use a jigsaw to cut out the circular pipe you’ve drawn. You don’t have to be precise. The flange will cover any rough cuts. However, the closer you get, the most solidly in place the pipe will be. 

From there, all you have to do is align the sewage pipe with the hole with the corner joint facing up towards the hole. 

1. Choosing a flange 

If you have Schedule 40 3-inch pipe (the most common sewage pipe used in households), you can choose a 3-inch flange. These are designed to fit inside a Schedule 40 pipe. 

If you have a 4-inch pipe you might need a 4-inch flange. However, a 4-inch flange can fit on the inside of a 4-inch pipe or on the outside of a 3-inch pipe. They’re the right choice if you either don’t know the size of the pipe you’re using or if your corner joint doesn’t directly line up with the hole and you’ll have to extend it. 

2. Cut your drainpipe 

Insert a short length of pipe into the drain and push it into the corner to the sewage. Place the flange on top. Then, measure the distance from the floor to the top of the flange and write this number down. Take the pipe off the corner drain. Measure the distance you wrote down from the bottom of the pipe and mark around the pipe. 

Keep in mind that the flange must always be installed on top of the floor. If you only have the subfloor in place, you’ll want to leave space for the floor to go underneath. 

Use a hacksaw or saw to cut the pipe. Then use a box knife and sandpaper to remove the edges and rough edges. This prevents toilet paper from getting caught and causing a clog. You can also take a moment to remove the flange cover at this time. However, if you’re leaving the flange unused for some time, leave the cover on. It prevents rainwater, debris, and dust from getting into the sewer. 

If you’re installing on concrete, you’d want to keep the pipe higher and cap it, pour the concrete, and then install the flange. 

3. Install the flange 

Check which size flange you have. If you have a 3-inch flange, you’ll want to apply pipe glue on the outside of the drainpipe on each end. Then fit it into the corner drain. Fit the flange on top. In most cases, you’ll have to apply some pressure to get it to fit into the hole. 

It’s usually important to put on disposable gloves before you start working with pipe cement. 

On the other hand, if you have a 4-inch flange and are installing it on a 4-inch pipe, the glue should be on the inside of the flange. Take care not to get pipe cement on anything else. It can be toxic and extremely difficult to remove. 

Then, use a drill and pre-drill the holes. This prevents your wooden floor from cracking when you put the screws in. Use the drill to drive screws made for use on wood to fix the flange. Wood screws are always flat at the bottom. They also do not have threading all the way up to the head. This greatly reduces the chance that the screws will crack or split the floor. 

Related Questions 

If you still have questions about installing your closet flange on a wooden floor, these answers should help. 

Do I need additional waterproofing around a toilet flange? 

Most toilet flanges come with a seal on the bottom. If you remove an old one, you’ll usually have to spend some time getting the old seal up. In most cases, that means you won’t need an additional seal. However, you do have to seal between the toilet and the flange. 

What if my toilet flange is below the floor? 

If your toilet flange is below the floor, you’ll have to raise it. Normally, toilet flanges end up 1 inch below the floor because they were installed in the subfloor. The person doing the installation forgot to make allowances for the actual floor. Unfortunately, you cannot install a toilet on a flange that’s under the floor. Here, you’ll want to remove the flange, increase the length of the pipe between the flange and the corner pipe, and then re-install it. 

Unfortunately, you might have to replace your flange with an extended flange if the current hole in the floor is too wide to attach a new flange. For example, if someone cut out the full diameter of the flange in the top floor to allow access to the flange. 

How to secure a toilet flange to the floor? 

Toilet flanges are attached to the floor using screws or bolts. Here, it’s always a good idea to pre-drill the floor. And, if you’re installing the toilet flange on plywood, you’ll want to attach a stabilizing board under the floor joists to attach the toilet to keep it steady. 

How do you install a toilet flange on tile? 

Installing a toilet flange on tile is exactly the same process as installing a toilet flange on wood. However, you’ll want to use a ceramic drill bit to pre-drill the holes for the flange. It’s also important to put rubber washers between the screws and the tile so that the tile does not crack. Otherwise, it’s exactly the same process. 

In Conclusion

Installing a toilet flange is relatively simple. Therefore, the only thing you have to make sure of is that you’re installing it on the floor, not on the sub-floor. Once you do that, it’s a simple matter of gluing the flange to the drainpipe. From there, all you have to do is attach the flange using a few screws.

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