Can the materials actually reach the site?
Measure the narrowest point on the delivery route and check steps, turns, overhead obstructions and carrying distances. Ask how materials will be unloaded and moved. Crane or lifting requirements should be priced before you commit.
What connects the room to the house?
Ask an electrician to assess power before the room is built. Cable route, trenching, supply capacity and testing affect scope. Plan data connectivity alongside power; relying on a weak Wi-Fi signal can undo the point of a garden office.
Who finishes the garden afterwards?
Drainage, paths, edging, disturbed lawns and access repairs deserve a line in the budget. Keep landscaping separate from the building quote so it does not disappear between contractors.
What turns a shell into your room?
Heating, ventilation, blinds, decoration, floor finishes and furniture add up. A gym or golf simulator needs equipment-specific clearances and loads. Ask for a complete list before choosing your room size.