Interactive floor plan: Heatherlands, UK

Extending houses might be architectural bread and butter, but for the best practices there's an awful lot of creative scope in making an existing structure bigger and better. Heatherlands is a good case in point. Beginning with a straightforward Arts and Crafts house from around 1912,

" target="_blank" >Satellite Architects Limited have designed a faceted annex that contains a pool, double garage, new living room and master suite, all wrapped up within an angular, wood-clad façade.

The site, on the Dorset Devon border in south-west England, is sweeping and steep, with plenty of private land, mature trees and distant views. The new extension steps down into the existing garden, its long sweep of roof dipping and twisting in order to preserve views from the original house. The old and new structures are joined lightly, with the newly created space between acting as a covered entrance way. Shingle cladding on the original house is mirrored by larch rain screens on the addition, tying the composition together. As well as a living room with generous views across the garden the annex includes a pool and gym area, the latter sunken down into the site. The three-level extension is topped by a new master suite, which is angled so as to have complete privacy from the rest of the house. Finally, well-placed windows look across to a restored Airstream trailer that acts as additional guest accommodation (an increasingly popular architectural device).

Satellite have ensured the extension is passively ventilated, with a solid core (housing the sauna and a wood burning fire) to store and circulate heat in the winter and plenty of openings in the monolithic façade to keep the interior cool in the summer months. While there's nothing modest about the generous increase in the original house's space and facilities, Satellite's skilful mix of modern forms, traditional materials and stealthy environmental measures are a fine advert for the gentle art of the extension.