Moving loo with concrete floor

[Theknittinggorilla]

I need to move a downstairs loo from one side of a boot room to another. It will swap places with a door into our kitchen. It's a concrete floor. The current loo is against an external wall, with an external waste pipe. The other side of the boot room is the party wall with next door.

Is this doable? And how? I can't see how the waste pipe will get from new loo to external wall as would need to cross the door. Even if expensive it would potentially be worth doing as it's part of a larger kitchen project and alternatives would be expensive.

Would appreciate thoughts of anyone who has expertise or has done this (piglet john?!).

I've attached a diagram...

what is the outside soil pipe made of? how old is the house?

It's lucky you have lots of money and are willing to spend it.

I think you will have to

excavate round the external soil pipe a hole big enough for a couple of people to stand in

dig up the concrete floor of the room

run a near-horizontal 100mm pipe, sloping slightly downwards in the trench, so that it can join into the drain you have dug up outside, or possibly a "manhole" if there is one nearby

put an elbow on the room end of the pipe so that it rises through the floor near the new WC position.

If the room floor is old you might take the opportunity to break it up and dig it out, lay a good base, DPM and insulation, and lay a whole new floor.

You will need Building Control approval and inspection. Avoid any contractor who suggests doing a non-compliant job in secret.

Plumbers are weedy little fellows with delicate hands, so look for someone calling themselves a Sanitary Engineer, or an experienced local builder with personal recommendations (not on a paid-for advertising website) whose previous similar work you can inspect.

Thank you piglet john.
100 year old house. Plastic soil pipe.
So expensive and messy. Boot room and kitchen will be ripped out and redone including flooring so it is going to be a mess anyway. Are we talking £100s, low £1000s? Alternative is swap the outside door and window around, which would also mean replacing and extending a concrete platform and stairs as house is 5 steps up from the ground. Trying to work out which is the cheaper option!

some thousand, perhaps.

100 yr old concrete floor likely to be thin, cracked and damp unless previously renovated, so will benefit from being dug up

Plastic soil pipe will be a replacement for the old cast iron, replacements might continue into the ground, if not, a crack and leak is likely, but easily fixed when you are excavating.

Any old drains around the kitchen might need renewing, and water supply pipe probably does too. All things to look at once you have your shovel out, and better done now than waiting until a problem occurs and you have to dig up your new kitchen.