A spare bedroom wins on simplicity
If you work from home occasionally and the bedroom is genuinely spare, moving in a desk can be the cheapest and easiest answer. There is no new building, no garden space lost and no walk outside in bad weather.
The trade-off appears when the room has to switch between work and guests, or when the office setup starts to take over storage and family space.
A garden office creates a boundary
Walking a few metres to a separate building sounds minor, but it can create a useful start and end to the working day. Calls, equipment and paperwork can stay in one place, and the main house stops having to double as a workplace.
That separation can be particularly valuable in busy households or roles with regular video meetings and concentrated work.
Design for the work you actually do
Desk depth, screens, background, daylight, acoustic privacy, sockets, data and storage should be planned together. A generic room with a desk added later rarely uses the footprint as effectively as a purpose-designed office.
Keep future uses in mind
A good garden office does not need to become obsolete if working patterns change. Sensible proportions, lighting and power can let the room evolve into a studio, hobby room or flexible family space later.