With walls built from local rubble stone, with traditional lime mortar and dressed stone details made by a local stonemason, this extension uses traditional skills and craftsmanship. Instead of using cheaper imported slate, the client chose local Westmorland slate with a stone ridge to match the original cottage. However, the traditional appearance hides a state of the art breathing wall construction timber frame made by Eden Frame.The walls and roof use Warmcel recycled newspaper sandwiched between timber panels with Swedish timber I-beams making efficient use of resources. The result is a highly insulated, energy efficient extension to a Victorian Cottage. The double glazed timber windows and french doors have Low-E glass with Argon fill and the floor is heavily insulated with Rockwool board. Velux Conservation low profile rooflights are used to keep the interior light and airy and to get the most of the morning and evening sun in the winter. The original cottage stone wall is left exposed on the interior and is used to store heat from the sun in winter and provide cooling in summer.A prefabricated solution was chosen by the client in order to meet a tight timescale. After the concrete foundation slab was cast, the prefabricated timber frame was erected in just over four hours. The building was water tight straight away so work could start on the interior at the same time as the slow process of traditional rubble stone walling outside.The extension provides independent living accommodation for the client’s elderly mother and is designed to allow conversion to a single space later if required.