For flats or maisonettes where there is a small entrance on the ground floor that is not separated by an external quality door the following procedure applies: -If the entrance area is less than 10% of the total floor area of the flat or maisonette, then it can be ignored. -If the entrance area is greater than 10% of the total floor area, the procedure is to enter this as an extension. This will allow you to specify what is likely to be a higher than average room height for the entrance area. This will not take into account the heat loss floor for the entrance area but does not significantly affect the SAP rating.