The development company Span built 30 housing estates across the UK between 1948 and 1984. Of the 30 estates, New Ash Green is perhaps the most ambitious project ever undertaken by Span. The company put up approximately half of all the houses in the village and did much of the design of the village environment.

In 1962, as part of the process of seeking planning permission, a document entitled 'A new village near Hartley Kent, New Ash Green' explained the fundamental intentions of the new village:

"This is an outline proposal to design and build an entirely new kind of village in attractive surroundings with all appropriate services and communal facilities for between five to six thousand people... One of the inherent qualities of the traditional English village is a sense of freedom in the surrounding countryside and the enclosed open greens, or spaces. In New Ash Green a compact and well defined village is proposed, embedded in the surrounding countryside... The architectural quality of the village will be achieved by a close relationship between buildings and landscape."

The houses are a mixture of types, the largest of which is a the ‘KL’ where, as Span said in a 1968 brochure, "the accent is on luxury, both in the spaciousness of the house… and in generous open ‘linked’ grouping of houses in the neighbourhood layout".