Bear House, Ashwell, Hertfordshire

Bear House Ashwell Herts

Agent: Oliver Cooper, Freeland Rees Roberts Architects Ltd

Architect As agent

Principal Contractor: FA Valiant & Son

Structural Engineer: Ed Morton, The Morton Partnership

Quantity Surveyor: Vernon Docwra, Vernon Docwra Associates

Mechanical Engineer: Meg Sandford, Roger Parker Associates

CDM Principal Designer: Colin Borley, Pimys Ltd

 

Bear House is a grade 2-star listed timber-framed former farmhouse dating from the early 15th Century.  The project involved sensitively restoring & conserving the whole house, which was in a very poor state of repair, to bring the accommodation up to a high modern standard. A new, light & contemporary ground floor extension was built to the rear.  As such, the project required careful collaboration between Freeland Rees Roberts  (FRR) and Building Control Surveyors to ensure compliance using high quality traditional & modern building materials & techniques.

Our Senior Building Control Surveyor Patricia James provided the site inspection service. Following her visits and timely comments FRR revised and improved some details, such as the junction of the Limecrete Floor with the modern blockwork walls of the extension. This ensured full compliance without affecting the construction programme.

Sustainability

The sustainability strategy employed a targeted, fabric-first approach, using traditional detailing to safeguard the building for a long life.  The extension is carefully oriented with large areas of glazing protected by a very large roof overhang.  This reduces solar gain in summer whilst allowing the winter sun to penetrate and warm the living space.

The construction uses traditional, renewable, low-embodied energy materials throughout. For example, the external walls are entirely re-covered with wood fibre insulation and lime render, replacing cementitious render. The new draught-sealed casement windows with night-latches and lime plaster provide greatly improved airtightness.  300mm of mineral wool insulation, with additional cross ventilation to protect the timber roof structure, insulates the loft floor. This fabric-first approach has hugely improved the thermal performance of the envelope.  Moisture harmlessly passes through the construction so that the existing oak frame is given the longest life possible.

A new high-efficiency gas condensing boiler was installed to serve a zoned underfloor heating system throughout the limecrete floor, which is controlled with smartphone-enabled thermostats.  High efficiency LED lighting features throughout.

Working Relationships

Information Good communication between the design team, 3C Shared Services and Hertfordshire Building Control ensured information was provided in good time.  The complexity and design risks involved with adapting historic buildings made this especially important.

An example of this occurred when changes were required to ventilate the loft, because the existing state and position of the rafter feet & wall plate that were uncovered during the works, meant that a combination of eaves and roof-felt-lap ventilation was required, where previously eaves-only ventilation had been designed.  Felt-lap ventilators are not a commonly used product but the acceptability, in this case, was quickly confirmed by HBC’s Building Control Surveyor.

Bear House, Ashwell

Problem Solving

Render for historic timber-framed buildings needs to satisfy a large number of performance criteria. It must be breathable to control moisture risks; lightweight, flexible and strong so as to accommodate movement in the timber frame.   In this case it was also vital that the render-background be a good natural insulator and be flexible enough to fit the extreme contours & distortions of the historic timber frame, thus preserving the lovely character of Bear House.

Finding a solution by using wood fibre insulation, carefully fixed to the frame in small board sizes, produced an organic geometry.  The Best of Lime Warmcote render combines the benefits of traditional lime render with strong modern fibres to resist cracking and an insulating aggregate to increase the wall’s thermal performance and reduce cold bridges.

Results

The project has resulted in a building that has exceeded the client’s expectations.  Bear House is a warm, delightful, unique home that retains all of its rich historic character.

Key historic features have been preserved, for example, the medieval hall-house layout comprising hall, service and solar; medieval wall paintings; the 16th Century screen with its apotropaic marks; the Quatrefoil and diamond mullioned windows.

Working together the Client, Architect, Structural Engineer, Services Engineers, Quantity Surveyor, Principal Designer, The Main Contractor & many subcontractors, Conservation & Planning Officers, Building Control Inspectors, Archeologist & Conservators, have managed to preserve the historically significant aspects of Bear House, whilst sensitively weaving in new features to enrich its story going forward.

Bear House was a shortlisted finalist in the LABC Central Region Building Excellence Awards 2019 for Best Extension or Alteration to an existing home.

This case study is written and credited to Oliver Cooper & Ian Lambert of Freeland Rees Roberts Architects

 

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