The loft buys floor area and costs headroom, stairs and warm air. For some households that is the right trade and for some it is the reason they move out.
The loft gives you the floor back
Lifting the bed above the living area frees roughly six square metres in an eight-metre house — the difference between a sofa and a bench. On MD 1 and MD 2 that is what makes the living space feel generous rather than adequate.
It also concentrates the whole plan around one staircase. Check the going and the rise on the drawing: a ladder is fine at thirty and tiring at sixty, and it is not a thing you change afterwards.
Headroom at the pillow is the number that matters
The clear height over the middle of the loft floor is not the useful measure. What matters is the height where you sit up in bed. Below about 1.1 metres there, most people knock their head every morning and stop using the loft as a bedroom.
Ask for that dimension specifically. It is rarely on a brochure and it is the single best predictor of whether a loft works.
Warm air rises, so plan the extract
A loft under an insulated roof collects the warm, humid air from cooking and showering below. Without an extract near the ridge it is several degrees hotter than the room and it is where condensation appears first in winter.
A ventilation valve at high level and an openable rooflight solve both. Together they turn a loft from a summer problem into a year-round bedroom.
A ground-floor bedroom changes who the house suits
MD 3 puts a closable room at ground level, and that is the model that suits people who work from home, households with a child, and anyone who does not want to climb a ladder at three in the morning. It costs living-room area, and that is a real cost.
It also ages better. A loft-only plan is a plan with a time limit for most owners, and that limit affects resale as much as comfort.
Storage under the bed is the free win
Whichever level the bed is on, the volume beneath it is the cheapest storage in the house — roughly 1.5 cubic metres in a standard double. Drawers on runners beat a lift-up base, which needs the mattress moved every time.
Specify it before production. Retrofitting drawers into a built platform means cutting a structural deck that was not designed to be cut.