A porch is exempt if:
- the floor area does not exceed 30m²,
- a door of external quality is retained between the porch and the rest of the house
- Glazing below 800mm in windows and 1.5m in doors and sidelights should be safety glazing.
- You are also advised to ensure that a porch does not cover outlets to boilers or other flues as well as the only ventilation openings to WC's and other rooms.