We have a bed semi-detached and are planning an extension to create more living space on the ground floor (single storey) and a fourth bedroom above the garage (if we get planning permission).
However, things keep getting added on, the most recent being a utility room! I don't need it at the moment - there are only three of us and the washing machine is in the downstairs loo and the tumble drier in the garage. But with a larger family and potentially a dog in the future I can see how it would be useful.
The only way to incorporate a utility room is to convert the back half of the garage (leaving the front part for bike and lawnmower storage). Access from the front to the back garden is currently through the garage (our garage is attached to next door so no side access), so we would have to traipse through the utility room with bins etc, but I don't see this as a problem.
However, although I don't mind not having a proper garage (it is really narrow anyway so we never put the car in it), I'm wondering if it would put off potential buyers. Is a utility room more valuable than a garage to buyers?