Single-storey house
All the main functions are on one level, which makes everyday movement easier and can be convenient for families with small children or for people who want to limit the use of stairs. However, a single-storey house usually requires a larger building footprint for the same usable area, which may limit the size of the garden or the possibility of building on a small plot.
Two-storey house or house with a usable attic
Spreading the functions over two levels allows a larger usable area with a smaller building footprint. This can be advantageous on narrower or smaller plots. However, you must take into account the stairs, the vertical circulation and the way the day zone is separated from the private zone.
Costs depend on the whole solution
Costs are affected by, among other things, the structure, the roof, the foundations, the floor slab, the area of the external partitions, the installations and the finishing standard. A single-storey house may have a larger roof and foundation area, while a two-storey house may require stairs and an upper floor slab. It is not possible to reliably point to the cheaper variant without comparing specific solutions.
What to check before choosing
Check the building footprint and height permitted by the planning documents, the shape of the plot, the position of the house relative to the points of the compass, the plans for the future use of the house and the needs of the household members. It is worth comparing both variants at the concept stage.