We have an under-stairs toilet that we are replacing. The toilet was quite old, so the drain was 20cm from the wall. Apparently newer toilets require the drain to be pretty much flush with the wall, so we need to put a stud wall in place. It's such a small wall (1.3m high by 0.9m wide) that I don't really want to get a carpenter out to do it.

I've read up on stud walls and the advice is to attach it to the joists above. In this case there is just a plaster ceiling and the stairs above. I don't really want to attach it to the stairs (imagine if the nails / screws went through!) and I think the plasterboard ceiling probably isn't sturdy enough.

So, a few questions

  1. What's the best way to attach the top horizontal wooden stud? I'm wondering if no more nails will suffice onto the ceiling plaster if the rest of the frame is well secured.
  2. How many (if any) vertical and horizontal studs/noggins do I need for a small wall like this, considering I need to run some pipes through it and potentially hang the toilet cistern on it. I'm thinking maybe one vertical and one horizontal?
  3. Any other advice?!

As ever, all advice welcomed :)

  • Why does the toilet need to be so close to a wall? Is there any problem leaving it with a wide gap behind it? You could put shelving or something in there....
    – wallyk
    Aug 24, 2013 at 23:32
  • What is beneath the plaster? You need to connect to structure. I don't understand the "toilet drains need to be flush to the wall" comment. Aug 25, 2013 at 4:27
  • The cistern needs to be hung on something, so it needs a wall there. I guess it could be a boxed in section with a shelf on top. That would save having to attach to a sloping ceiling...
    – x3ja
    Aug 25, 2013 at 8:38
  • Beneath the ceiling plaster are the wooden stairs. The drain is in the floor about 20cm from the existing wall. Modern toilets sit with their cistern directly above the drain, so the wall needs to but up to the drain. That means we need a wall there - or at least something to attach the cistern to.
    – x3ja
    Aug 25, 2013 at 8:40
  • 2
    It sounds like you're referring to a wall mounted toilet, as opposed to a floor mounted toilet that many people here may be more familiar with. If so, you may want to include that detail in your question.
    – BMitch
    Aug 25, 2013 at 12:45

1 Answer 1


You need to locate and identify the underlying structure, where and what. Only then can one determine the best attachment method and wall layout. Stairways typically have stringers under them running the length of the stairway run that you can connect to. But there are endless variations on stair construction, so only someone on site can determine this. There are various devices for locating underlying wood structure, their effectiveness varies by local conditions.

Stud framing is typically 40.5 cm spacing on center, so you may need two intermediate studs in addition to the end studs. You need solid blocking flat to the mounting face in order to mount plumbing fixtures. Some hardware needs to be framed into the wall, so you need to identify exactly what hardware is used in order to provide and locate any needed structure.

Unless you can provide all this information, no one can adequately tell what to do in enough detail to ensure proper construction.

  • Thanks for the pointers. I think we're going to avoid making a stud wall because it sounds way too complicated. Think we're going to just do some get a box unit to enclose the toilet cistern and bridge the gap to the old wall... should make things a lot simpler.
    – x3ja
    Aug 26, 2013 at 17:17

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