Ashfield

Ashfield is one of Green Oak Architecture’s FIRST commissions. The ‘cross wing’ in the foreground of the photo forms part of a substantial new extension along with a rear facing single storey conservatory. Built to match the existing oak frame with its rendered panel infill as closely as possible, there is one important exception; the original oak frame was panel infilled with the frame exposed both internally and externally, making the thermal and weather performance of the building poor due to weather and air tightness, and cold bridging issues. Working with the clients we decided follow a well tried and tested solution of separating the internal structural frame and the external cladding frame. The internal frame is the main structural component of the building as can be seen from the internal photos and carries the insulation; the external ‘cladding frame’ forms the outer leaf of structure carrying the render panels. The external frame is formed of well air dried oak sections to ensure stability. Behind this is a fully vented cavity, MCL and insulation. The insulation is set continuously external to the structural frame, as well as being set between the frame members, all of which ensures a high performance trouble free envelope that looks every bit as good as the original structure but without the shortcomings. (Photography: Duncan McNichol)

The rear facing single storey extension doubles the size of the kitchen. A ‘direct glazing’ system carries the fixed double glazed units, as well as the joinery openers. The master bedroom has a ‘Juliette balcony’ with outward opening French windows guarded by a glass handrail internally. The flat roof of the single storey section ensure views from the upstairs bedrooms are not obscured. (Photography: Duncan McNichol)

Spot the new section of this traditionally panel infilled oak frame. We have done our best to match the existing as closely as possible, once weathered in we think it will be nigh on indistinguishable from the original structure. (Photography: Duncan McNichol)

Flat top trusses have large glazed roof lights to make a beautifully lit interior to this comfortable family kitchen. Two pairs of Bi-fold doors open most of the wall facing the garden bringing outside inside when the weather is fair. (Photography: Duncan McNichol)

The heavily beamed ceilings of the extension match the original structure, which in fact was completed in 1991. Pairs of spine beams set either side of the chimney ensure symmetry within the room and frame the fire place. (Photography: Duncan McNichol)

The master bedroom is constructed with sling braced trusses, a form of raised tie type truss increasingly popular, and which if well-proportioned is most attractive. Note the glass balustrade of the ‘Juliette Balcony’. (Photography: Duncan McNichol)

The en-suite bathroom to the master bedroom is also oak framed and we think this is a very successful adaption of the oak frame style to make a beautiful room. For this scheme we built a ceiling over the bathroom to create an open loft in the master bedroom which is accessed by a galley style ladder, adding a sense of fun and informality to the room. (Photography: Duncan McNichol)

As already stated, the problem with panel in-filing between the oak frame members is the performance of the system at the panel edges, as well as cold bridging. When we extended the original frame which was panel infilled in the traditional manner above, we had to find a way to avoid cold bridging of the timber, and resolve water and air tightness issues. These examples of the drawings produced by us show our solutions to these problems.

Insulation is placed between the oak frame members in the usual manner but also outside. An air vent is created outside the insulation created by thin battens, to which we fixed a carrier board which was rendered.

These last items are fitted between air dried oak cappings which are screwed and plugged into position. This carefully considered and detailed system did much to improve the thermal and weather performance of the envelope of the entire extension, whilst still giving the appearance of a traditional panel infilled frame. Success – though not easy!

We would like to commend the excellent work of R J Coles who were the master builders and who’s craftsmanship was beyond reproach.