How to Deal with Odd Size Toilet Rough-in

Odd Size Toilet Rough-in

Don’t Lose Sleep Over an Odd Size Toilet Rough-in

It absolutely sucks (almost suicidal) to have a non-standard rough-in size for a standard toilet. You will have limited toilet options, to begin with, and then the installation may cost twice as much as the toilet.

So, if you are in the planning stage for your new bathroom, Congratulations! Please stay clear of all rough-in sizes and insist on a 12-inch measure from the finished wall (not the baseboard) to the center of the floor flange.

Don’t buy into the BS that a 10-inch rough-in size will save you some bathroom space or, for whatever reason the 14-inch offers, hang on tight with the 12-inch rough-in. It will save you a ton of trouble and frustration when looking for a replacement later.

That’s because every toilet maker (local and foreign) who wants a piece of the US market must carry the standard 12-inch rough-in for all its toilet series. Even the smallest of compact toilets come with a 12-inch rough-in.

Sure, there are 10-inch and 14-inch toilets out there, but the range is not as extensive as the standard 12-inch. Some makers don’t even bother to come up with anything other than a 12-inch rough-in.

What Are Your Options If You Are Not Having a Standard Rough-in?

But let’s define what is considered ‘Odd Size’ for a toilet rough-in.

In fact, the 10 and 14-inch rough-ins are also standard sizes, besides the 12-inch. It is just that they are not as popular or prevalent compared to the 12-inch rough-in.

You are more likely to have the 10 or 14 inches rough-in if you bought an old (30 years or older) house. Or worse, some will have 10-1/2″, 11″, 13″, and 13-1/2″ for a rough-in. If you are in such a situation, what are your options?

Here are some suggestions if you don’t mind a little modification to the drain pipe. And it’s important to note that these options may require professional assistance and could result in higher costs than a standard installation.

1. Get a Matching Rough-in Toilet: This is the easiest and lowest cost, but it may be limited in options. You can search for a toilet model matching your rough-in size, like a 10-inch rough-in toilet. But finding the style or features you want may be challenging, even more so if it is a 14-inch rough-in toilet.

No hacking of the floor and replacing the waste pipe is required with this option.

2. Redo Your Drain Pipe: This option gives you the widest range of toilet options but requires more work and expense. You would need to remove the old drain pipe and install a new one with a 12-inch rough-in.

This option requires hacking the floor and probably the wall as well to access and replace the waste pipe.

3. Use an Offset Flange: This option involves installing an offset flange connecting your drain pipe to a standard rough-in toilet. It can be tricky to install, and you must ensure the offset flange is properly aligned with the toilet’s waste pipe. Experience will ensure a proper fit that will be as good and lasting as the original toilet flange.

Hacking of the floor is required with this option.

4. Get a Toilet with Flange Adapter: Some toilet manufacturers offer flange adapters that can be used to connect a toilet to a 10 or 14-inch rough-in. This is a good option if you can find a toilet model that you like with this feature.

The KOHLER Corbelle and TOTO Carlyle II use a flange adapter to address the need for 10, 12, and 14 inches rough-in. All you need to purchase is the right adapter size along with the toilet.

No hacking of the floor and replacement of the waste pipe is required with this option.

You Are Safe with an 11-1/2″ or 12-1/2″ Rough-in Measurement

Though not so ideal with that half-an-inch difference, you can still get a 12-inch rough-in toilet in place within a whisker.

The toilet is not a high-precision device, so its dimension will always vary. This means the actual product may have slight variations to the dimensions on the spec sheet. Be it with the rough-in measurement, the gap distance between the wall and the back of the tank, or even with the flange bolts.

You can use these allowances to adjust the toilet to fit the floor flange. The result is usually a wider or narrower gap between the wall and the back of the tank. You are good to go as long as the tank is not tightly pressed against the wall. A wider gap than what the specifications suggest is also fine.

Making these fine adjustments reduces the discrepancy and is perfectly patched by the wax ring. So if you have a rough-in size that is a little less or more than the standard measurement, there’s nothing to be concerned about.


It’s essential to weigh your options carefully and consider cost, ease of installation, and design factors when deciding on the best option for your non-standard rough-in.

But converting to a 12-inch rough-in is a permanent solution worth considering. The conversion cost may be high, but it opens up an endless range of 12-inch rough-in toilets when the need for replacement arises. And perhaps, your property might appraise at a higher value with this little plumbing upgrade. Just saying.

Leave a Reply

Your email address will not be published. Required fields are marked *