The London-based practice has clad both the front and rear asymmetric extension in cedar
Sam Tisdall Architects was commissioned to refurbish, fully insulate and extend a semi-detached cottage on Baldock Way in Cambridge. The house was originally set back from its neighbours with a small rear garden, so planning permission was obtained to extend the property to the front, accommodating a new study. Internally, the architect has replaced a narrow entrance corridor with a larger hallway by opening the reception room to the corridor. This has allowed for a new stair to replace the existing steeply winding staircase.
To the front, the extension’s form is asymmetric with a sloping roof to one side, topped with a rooflight and both walls and roof clad in cedar boarding. A poorly built extension to the back of the house has been also clad in cedar and reconfigured to provide a kitchen and dining space. This has been extended to first-floor level to provide an additional family bathroom with ensuite.
Finally, the existing house has been re-insulated with an external render system. New windows have been added while the loft has been converted into a bedroom with the chimney demolished to make space for a shower room.
Utilising a light palette of materials and colours, the house has lye and white oiled Douglas fir floors and light tones for walls and ceilings. Tongue and groove panelling has been used in the study, bathrooms and to the side of the staircase.
There were two elements of the scheme which were considered in particular detail.
The first was the external cedar cladding. Originally proposed as more traditional cladding, with the encouragement of the client it developed into a more refined rainscreen of 90mm-wide cedar battens with 10mm gaps. Behind this, there is a UV stable black breather membrane to the walls and a single ply membrane to the roof. By using a rainscreen we were able to detail gutters and eaves with no flashings or copings. To fix cladding to the roof proprietary fixing bars were used. These are typically used to fix solar panels and can be welded to the roof membrane which is continuous underneath. Careful attention was paid to setting out so the windows coordinated with the cladding, with no cut boards.
The second element was the new staircase. Made from solid Douglas fir, it required careful detailing to hide the fixings of the blackened mild steel handrail and close co-ordination between joiner and metal worker. Pre-finished sections of handrail were slotted into place through rectangular holes drilled in each tread. Each spindle was then fixed to a set-back cut stringer and the stair edge clad with an MDF fascia. The sections of handrail were then welded together to form a continuous handrail and the blackened finish touched up. This process traditionally called blueing is used for blackening weapons (think black revolver) and is achieved with a mix of chemicals which the metal worker had to learn how to use to get the correct effect.
The staircase continues up to the loft to a landing which bridges over the stair void with a double-height space beyond. This allows light from a large fixed window down to the first floor as well as giving a sense of space.
Sam Tisdall, partner, Sam Tisdall Architects
Start on site September 2017
Completion August 2018
Gross internal floor area 158m² including extension; 110m² existing only
Form of contract Traditional (JCT MWD 2016)
Construction cost Undisclosed
Architect Sam Tisdall Architects
Structural engineer Structural Engineers Cambridge
Approved building inspector 3C Shared services
Main contractor Cambridge Building Company
CAD software used Vectorworks