Do you need planning permission?
The local council will need to be involved. Any alterations to a house's drainage system need building regulations approval. And you will definitely need planning permission if your house is listed or you live in a conservation area, for example. Make sure you talk to your local planning department before you begin. Finally, any changes to your home's water supply may need to conform to local water by-laws, so you should double-check your plans with your local water company.

So how much money will it cost?
Although you could install a basic bathroom and erect a simple partition across a large bedroom for as little as £1,000, you probably won’t get the added value you’re after. For this, you’ll need a well-constructed, sound-proofed partition and good-quality bathroom fittings. You might also need an extractor fan, and if drainage is a problem, a macerating toilet with pump. If space is tight, you might want to employ an architect to get the most from the project. All this could raise costs to £5,000 or more.

And how much value will it add to my home?
The exact amount an ensuite bathroom will contribute will vary depending on your property and its location. For instance, you'll get a greater benefit from adding an extra bathroom to a five-bedroom house with just one bathroom than to a one-bedroom flat which already has a bathroom. And as always, your local estate agent is the best person to tell you exactly how much added value an ensuite will bring you. However in general you can reckon on adding anything between 7 and 12% to the value of your home – more if you live in an urban area such as London.

Before you proceed
Think about employing an architect as they can often come up with options you hadn’t thought of, recommend local builders and sometimes offer project management for an additional fee – this can be important if you can't spare the time to do it all yourself. And if you’ve seen an ensuite you like, find out who did the work and try to use them. Get several quotes and ensure that any contractor belongs to a trade body and has public liability insurance. The work will also need to comply with Building Regulations - you can find out more from Communities and Local Government website.