Single Story Rear Extension Plumbing Help With Existing Required

2 Dec 2019
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United Kingdom

We’re currently going through planning in anticipation to build in the spring, part of the planned work is a single story rear extension to build a dinning room off the existing kitchen.
I’m from a trade back round so looking to do a lot of work myself but after a little help with the existing plumbing set up.

The next extension goest straight on the back of the kitchen and simply the existing doors and window are coming out and it’s being refinished at the tide in to the new extension, currently there are drainage pipes coming down the back wall to gulley, they are from the sink and dishwasher,

this wall is going to be plaster boarded and finished, and kitchen is staying as is ,
what do I do with this pipe work? I don’t want to box it in as want the wall flat.
so do I chase and set the pipes in to the wall and set the gulley back slightly in to the wall ? I won’t be able to have an open gulley as it won’t be maintainable so need some advice on what to do?

thank in advance ,
P.S I don’t know where the gulley runs too yet so it could get more interesting, just after knowing what I should do.


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I would have thougt that if you want to conceal these pipes etc and the the gully cant be open then it will need to be vented. Is there not a soil stack nearby that these could run into?
there should be room behind the kitchen cabints to run your pipes inside and then poke them through the wall in a different position. I'd say you would have to re position the gully anyway which will be easy to do when diggin out the new foundations. maybe put it right up to your boundary with next door if there will be room?
The existing gully needs removing, as do the existing external waste outlets back to inside the kitchen.

You then either need new 110mm waste pipe or alter existing.......wherever that finishes will determine where you take the new waste from the kitchen, it needs to come through just above concrete slab level, ie in insulation layer.

Ideally you want to alter kitchen side so only 1 waste come through.
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Cheers for your thoughts all,

Sadly the extenstion is going full width up to fenceline so no room to move the gulley to the side. There is no room behind the exissiting units to run pipes as the dishwasher and washing washine are up against the internal wall.

i was thinking of taking out 5 courses of bricks about 8 wide where the waste pipes come out and then put a concrete lintel in above the new opening (no loading as its below the window opening) then i have the brick width and cavity to set the waste pipes in and look to set the gully back slightly also in to this opening and replace with a vented stack, then just plaster board over the front and finish.
Sounds over complicated. Surely stud wall boxing is easier the full width of remaining wall so it looks like a normal wall and ran low along new boundary wall in some boxed off skirting to exit extension into new gully?
Taking out the wall 100mm or so could be the answer, I need to batten it anyway for the plasterboard finish, what would I do with the gulley do I just replace it for a vented trap?
I won’t know what way the existing pipe work runs until the dig begins so that might change things anyway

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