Hi, my Wife wants a downstairs toilet and for years I have resisted losing my garage as I keep my car and tools and stuff in it, but it is a fairly long garage with half of it inside the house, under the upstairs bathroom, so plumbing and waste are not really issues, I have measured the spare space and there is enough space at the end of the garage to put a toilet and sink and still get my car in, there is already a door from the house to the garage. I am guessing that as I still want to use the garage to hold my car that a stud wall will not be sufficient and I will need to use bricks or blocks, am I right?

Why would you think you would need a block wall? You're focusing on partitions and storage when you should be figuring out where to connect to the main.
How close is the sewer line to the garage? Can you tap into the house main? I moved you over to The Plumbing Page for a reason. Think plumbing since that will be your biggest hassle. Back to you, Tom

YUP! Check your local plumbing codes and see if WET VENTING is allowed. If wet venting is allowed it will allow you to use the sink vent to vent the toilet. If wet venting isn't allowed you'll need to vent both the sink and the toilet individually and connect those vents together to run a new 2" vent over to a "future vent" (if present in the basement) or a vent upstairs, OK?

Back to you...

Mark

Regardless of drain and vent issues, a stud wall would be fine.

Agree with above Experts: stud wall is OK to go with. Milo

Let's get back to the important stuff, The drainage. Let me repeat my questions.
How close is the sewer line to the garage? Can you tap into the house main? Let me know, Ton

Hi, thanks for all your replies, the soil stack is also at this end of the garage so was hoping to be able to tap into this, the stack is not in the exact place of the proposed toilet but near where the existing door into the garage is so would require some pipework. The garage floor is 150mm lower than the house floor so I would want to come up there so was hoping the waste could go under the raised floor to connect to soil pipe. (I wasn't sure about needing to use bricks blocks because of still using the garage for a car and was thinking of fire regulations but I suppose using fire retardant plaster board would be okay, this is good news as I have done stud wall before.)

Of course it would be better to break up the floor and do it right but I'll go along with platforming the floor, What material is the soil stack? If you connect the sink drain to the toilet drain the toilet will be wet vented by the sinks vent which you will run out the roof. Good luck, Tom

The soil stack is boxed in at the moment but it is plastic at the top end. Looking at it more I think I may have to dig into the floor as I get closer to the stack to give it enough angle. Can you explain about the venting as a little unsure about this. Thanks. Paul.

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Can you explain about the venting as a little unsure about this

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Let me explain about vents. When you pull a plug or flush a toilet the water going down the pipe sets up a suction. This has to be relieved by outside air. Hence a pipe through your roof. If the vent is blocked by a birds nest or a dead critter the water will pull suction through the nearest trap and you will hear a gurgle. It may be a fixture trap or the toilet may talk to you but you will hear it someplace. While it is possible for the suction to pull enough water out of a trap to have sewer gas escape but it's more likely a smell will come from decaying food, grease or hair. Every fixture that has a trap MUST be vented. And now you know about vents. Good luck. Tom

Thanks, now I know roughly what I'm up against, I think I'll be okay, not going to start for another month or two, got to sort the garage out first, whole heap of junk in there!

Just let us know if we can help. Good luck, Tom