Mowat & Company used timber sourced, milled, fitted and finished on site to help keep its refurbish and adapt project on track within tight budget and carbon constraints
Whitney Sawmills is a charity-owned sawmill specialising in British grown timber on the banks of the River Wye in Herefordshire. It was established in the early 1990s by a local craftsman who took advantage of the strong westerly winds from the river on the long flat site, previously the location of an old railway station, to begin milling and drying his own supply of timber.
Architect Mowat & Company was approached by the charity Woodland Heritage, who bought the site in 2016, to look at ways to increase the production capabilities and improve the customer experience. From the outset, both the charity and sawmill manager were keen to reuse and refurbish the existing buildings, with the best applications for the wide variety of timber coming through the mills from the neighbouring woodlands.
This developed into a site-wide strategy for ‘upcycling’ the existing buildings to create a coherent identity for the piecemeal additions that had been added over time. Instead of knocking down what was once there, the team was determined to retrofit the old site and re-use what it could to save on material cost and waste to landfill. Following this pattern, our design centred around the reuse and adaption of two of the forestry buildings, using timber products grown and felled on site, to accommodate a new office/reception and a new timber store, both within the footprint of two industrial sheds that hav been made low-carbon, low-energy and low-cost.
How and why we did it
Circular economy principles were employed throughout to reduce carbon and costs, including reusing the frame and timber from the original sheds.
Adapting the buildings presented a clear set of constraints within which to work. On what became the reception building, the end bays of an existing, steel frame, open-sided wood store had previously been infilled to create a saw doctors’ room for sharpening tools. However, the timber frame infill was poorly insulated and no longer weathertight, presenting the opportunity for careful adaption and extension. Working with the sawmill manager we developed the design for a distinctive entrance building following the form of the shed, with slatted stained larch cladding and featuring a chestnut column set to one side, which acts as a beacon for visitors and staff.
Main contractor Smith Builders stripped back and assessed the structure and ground floor slab, which were largely in good condition. The level of the slab was too low in relation to the external ground level as the site had developed and grown up around it. Working closely with its subcontractor RB Construction, the team came up with a practical solution which ensured that the final finish and aesthetic of the design was maintained. A 100mm topping slab was poured to provide a level sub floor and increase the structural depth. The increase in height was made up by raising the ramped entrance and Douglas fir decking area.
To heat the space, the building incorporates a traditional log-burning stove that burns scrap wood from the sawmill. Another challenge was to achieve the outlined insulated values within the budget and existing structure to make the most of the stove’s energy output. The original option to infill the timber frame with hempcrete was discounted due to the high costs of installation and shuttering, and the structural stability it added was not needed. In this case, we developed an alternative detail for the internal lining, using a mixture of wool and Rockwool insultation between the existing studs and additional timber battens to provide energy efficiency and cut energy use.
Learning from the project
The resulting building is a testament to the knowledge of the client and contractor who found ways to work to the limited budget without compromising the original design intentions.
The nature of working with an existing building, where discoveries arose on site, together with the use of non-standard materials felled directly from the neighbouring woodlands, meant that the project team had to respond and adapt to changes along the way.
We were able to draw on the expertise of the sawmill manger to specify the right timber and finishes for the right application, from the unfinished chestnut column, stained larch cladding and Douglas fir decking for the exterior, through to the smooth sycamore desktops and joinery with contrasting walnut lipping inside. The builder was particularly pleased with the burr oak display piece repurposed and reshaped by its sister company Cut Designs, which now serves as a reception desk and focal point to the office interior.
Repurposing the existing structure and foundations kept the costs and embodied carbon involved in the construction as low as possible, particularly when combined with timber sourced, milled, fitted and finished on site. Operational carbon is estimated at 3.83 kg/m2/a based on the projected electricity use for lighting and hot water, with space heating provided by a stove fuelled by biomass from wood waste produced on site. Smart design features, made with locally sourced and sustainable materials built to last, mean visitors to the charity-run sawmill can now feel warm and welcomed, while browsing the large selection of British Woods that the site has to offer.
Orlando Hill is a project architect at Mowat & Company
On-site duration 8 months
Contract value £75,200 exc. VAT (reception building)
Approx area 43m2 (reception building)
Architect Mowat & Company
Client W H Timber
Main contractor Smith Builders
Key suppliers Whitney Sawmills, Ty Mawr, Holt by Algood