Who do I need to consult....

[Wingedharpy]

to tell me if I can extend my house in the way I have imagined to build a downstairs shower room?

The house is a terraced house and we want to extend at the back and side but the pipework for the existing drains run parallel the side of the house and I think I'm right in saying that you cannot build over drains.

So, who do I need to tell me what can and cannot be done?
Architect, builder, structural engineer?

Go to the end of your garden, look back at the terrace and see what everyone else has done, this tells you what may be possible.

How big is your outside space?

and you can build over drains, you just have to add access hatches, and be wise about how it is done.

you do need to submit plans, these do no have to be drawn by an architect.

Find the best builder in the area, have a meeting, they will tell you what is realistic, for the space and budget.

they will recommend who can draw up the plans,

and if you really have found the best builder be prepared to wait, as if they are good they are unlikely to be available for a while.

Thank you.
No-one along the terrace has done what I want to do but this may be because the houses are quite large and people tend to go up ie. convert the loft, to give extra bedroom/bathroom space.
This is not what I want as I'm looking to this with a view to accommodating an elderly relative.
Next question - how do you find a good builder? How do you know who is good?

look at all the other terrace in the immediate area,

how do you find a good builder?

you don't want a good one you want a great one.

ask about, find someone who has been in business for at least twenty years trading under the same name,

go and see work that has been done in other people homes,

Look at the finishes, corners and edges, look at the shirting boards, if they are perfect they were not rushed, there will be things you notice and think how clever, (if there isn't anything that jumps out as brilliant, the builder doesn't have the ability to think ahead and work backwards to make a perfect finish) if anything jumps out at you that is annoying, walk away, there is no excuse to have anything annoying in finishes,(or any other part of the build)

Anyone good does not need to advertised and are book up a long way in advance, most their work is repeat custom, their name is passed along through happy clients.

and wait until they can fit you in, it will be worth it.