Can I put a shower room or kitchenette in a detached garage conversion?

Yes, where drainage allows it, and guest suites are one of the most popular reasons people convert their detached garage. The practical limit is how far waste has to travel to reach a drain. The main thing to consider is that once a space has both a shower room and cooking facilities, it stops being an extra room and starts being treated as separate living accommodation, which changes what you need to apply for. We check that position at the first visit so the design does not have to be unpicked later.