Fallahogey Studio, Kilrea, Co. Londonderry

Introduction

McGarry-Moon Architects has designed a new studio for the award-winning practice, set in the lower garden of Jessica McGarry and Steven Moon's own home, Fallahogey House, which they designed and completed in 2005 in the rolling countryside of Kilrea, Northern Ireland. The building houses a new studio for the expanding rural practice, together with a garage and a level access bedroom with shower room for relatives with mobility issues.

Externally, the building is a tall and simple pitched roof form, its shape a reference to the vernacular agricultural barns of the local area. Like many of them, it is clad with weathered metal sheet, but in this case the use of Cor-ten panels with their deep rust colour, clean lines and seamless surfaces gives a contemporary character. Both gables are clad with perforated Cor-ten panels set in front of large triangular glazed panels, helping to flood the building with daylight. When the office is lit at night the triangular glazed panels glow like lanterns.

In contrast, the interior is a birch plywood glulam structure, expressed and celebrated to create a series of light-filled overlapping spaces which can be used in a variety of ways by the practice. As the architect explains: ‘The joy of craftsmanship and tactility of the timber imbue the space with a timeless beauty.’

The birch plywood glulam structure is left exposed internally and doubles as the interior fit-out, forming the wall finish, shelving, drawers and cupboards.

The main entrance, a glazed door in the gable at mid-height, is reached by means of a Cor-ten steel bridge with perforated Cor-ten balustrades. It is slightly skewed on plan and passes through a canopy of mature apple trees. The entrance level houses an accessible bedroom/shower suite, used for guests and relatives but which can also act as a private meeting room. Stairs ascend to an upper mezzanine level, a meeting space within the open pitched roof volume, lit by a long rooflight, and steps downward lead into another daily meeting space, flanked by generous open shelves. This overlooks the main office space on the lower ground floor, an insulated cast in-situ concrete semi-basement partly sunk into the ground up to work surface level, where a strip of continuous glazing gives views across the garden. The basement also houses a small kitchen and, at one gable end, a domestic garage.

Construction

To reduce its visual impact on the landscape and to maintain the privacy of neighbours, the new building nestles into its sloping site, making use of the slope to create a series of different levels with the lower ground floor level, the studio excavated and tanked with cast in-situ concrete. The lower ground floor level studio worktops, walls and floor are of 100mm polished cast in-situ concrete as is the landing and staircase which lead down to it. On the north west side of the building, the slope gives ground level access to the garage, also lined with fair-faced cast in-situ concrete walls. Each level is connected by a half-flight staircase.

The main structure consists of a series of plywood glulam portal frames supported by the concrete semi-basement. The wall columns extend to the eaves and are braced horizontally with plywood glulam beams and purlins. The rafters were pre-fitted to the columns with concealed stainless steel flitch plates and connected with stainless steel dowels. Sections of portal frames were then lifted onto the building by crane and connected at the ridge.

The glulam structure is lined with 18mm birch plywood, with an airtightness membrane applied to the outer surface and with 200mm of insulation fixed to the outer face. The rainscreen cladding of 4mm Cor-ten steel sheets is mechanically fixed through the insulation to 25 x 50mm battens and counter-battens on a breather membrane.

The use of timber

To minimise waste, the structure was designed around the dimensions of a plywood board, an insulation board and a Cor-ten panel. The PEFC- and FSC-certified birch plywood was sourced from the Ukraine as 1200 x 2400mm boards. The plywood components, together with all their joints and connections, were prefabricated and painted off-site by a local joinery company to allow for quick and simple on-site assembly.

The use of plywood boards to fabricate glulam components had several compelling advantages; it was sustainable, very economical, light in weight yet high strength. Exposed in the interior, the plywood glulam beams and columns express the structural form, at the same time acting as internal features – picture shelves, bookshelves and worktops.

Behind the portal frame structure, the interior walls are lined with 18mm plywood boards. They act as diaphragm walls to additionally stiffen the structure while creating a resilient wall surface with a delicate finish of white-painted timber graining. The staircases are all formed of double 18mm birch plywood treads and risers fixed to a supporting framework of box-like open 18mm plywood shelves, used as bookcases.

The use of plywood for structure and walls meant that wet trades such as plastering were eliminated, speeding up the construction process.

Each structural plywood component was drawn individually by the architect to show width, length and the final thickness – ie the number of layers of 18mm plywood – of each component depending on its position in the structure. For instance, the principal portal frame wall columns and beams are fabricated of nine thicknesses of 18mm plywood to achieve a final thickness of 162mm. The mezzanine floors are supported by 400 x 126mm plywood glulam beams (seven thicknesses of 18mm plywood) and support 170 x 54mm plywood glulam joists (three thicknesses of 18mm plywood).

The 1200 x 2400mm boards were cut to size by the architect and his brother, the contractor. The boards were then bonded together in another workshop to form the final glulam components. The columns are connected to purlins and beams with prefabricated dovetail joints. The two sides of each column were CNC-cut with a series of rebated notches, and the beams and purlins were fitted with projecting plywood dovetails with curved tops which slotted into the notches.

Sustainability

The architect states: ‘We have been mindful from the outset of our design process that it is vital to minimise the impact of the proposal on the environment. We have made great efforts to curtail the building’s ecological impact during both construction and occupation. Our chosen method of construction was birch plywood glulam timber frame. This ensures the building could be constructed quickly, efficiently and to excellent standards both in terms of airtightness and thermal performance’.

The building is constructed to Passivhaus standards to provide a high level of occupant comfort while using very little energy for heating and cooling. The standard is achieved through the use of high performance triple-glazed windows, high levels of insulation and rigorous detailing of the construction, which is free from thermal bridges and is airtight.

All trades involved in the construction of the project were local, reducing the carbon foot print/embodied energy during construction and increasing social sustainability.

Awards

Wood Awards 2018 – Commercial & Leisure, Highly Commended

RIBA National Award 2017

RIBA Northern Ireland Award 2017

RIBA Northern Ireland Small Project of the Year Award 2017

RIAI Award 2018 Commercial/Workplace Winner

EU Prize for Contemporary Architecture, Mies van der Rohe Award 2019 – Nominated

RSUA Design Award 2018

RICS Awards 2018 Design through Innovation Shortlist

RICS Awards 2018 Commercial Shortlist

RIBA Stephen Lawrence Prize 2017 Shortlist

Blueprint Awards 2017 Final

Completion Date:

January 2017

Building Type:

Office

Location:

Kilrea, Co. Londonderry

Architect:

McGarry-Moon Architects

Structural Engineer:

Structures 2000 Ltd

Main Contractor:

Alan Moon Joinery and Building Contractor

Joinery:

Alan Moon Joinery and Building Contractor

Glulam Structure Manufacturer:

Old Manse Joinery

Timber Supplier:

Brooks Group, Dublin

Timber Elements:

Structure, internal joinery

Timber Species:

PEFC- and FSC-certified Ukrainian birch plywood

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