Project Information

Background

Anglesey Abbey is well known for its gardens, which offer superb vistas and an impressive collection of plants within a formal arrangement. Visitor numbers to this National Trust property have risen to over 180,000 per year and in recent years this has placed a strain on the visitor facilities.

Prior to the opening of the new buildings in July 2007, the facilities comprised a teahouse constructed in 1975, which had undergone 11 extensions. Very few buildings look or work well after this many alterations!

The new facilities deliberately straddle the car parking on the east side and the formal gardens on the west. Helping visitors to undertake the transition from arrivals and parking to the much calmer environment of the gardens is a very important goal of the new facilities. Part of the National Trust’s brief to architects Cowper Griffith was to ensure that the gardens definitely remained the main attraction – the centre, whilst being attractive, was to be ‘recessive’, rather than becoming a competing feature to the gardens.

An important factor in achieving this goal was the design of the glazing and associated shading. The client wanted visitors to enjoy seeing the garden from the centre but did not want those in the garden to be too distracted by the building especially reflections on large expanses of glass.

Louvred screens providing ‘filtering layers’ were used in various locations – two particular elements of which are the subject of this Timber Solution. The first is a wooden louvred system constructed in the gable ends of the east and west facing elevations, which was used in combination with other solid and glazed elements in the gable. The second is an external sliding louvred wooden panel arrangement installed in front of three aluminium sliding doorsets on the south elevation.

Location of the louvred elements

The main east and west gable walls ‘pick from a palette’ of shaded and non-shaded glass and timber clad wall details, to provide the optimum design, in terms of meeting both the requirements of the building and controlling cost. The site plan provides a general arrangement of the ground floor and identifies the location of the five elevation arrangements, which are described below. The three external sliding louvred frame arrangements, D1, D2 and D3 are shown on the site plan on the south-facing wall. Each of these gives access to the external seating areas and decking in an enclosed garden area, which visitors are encouraged to use on sunny days to increase the capacity of the restaurant. The purpose of these sliding louvred frames is to provide attractive filtered light as well as control unwanted solar heat gain.

Design challenge

There were many issues to consider simultaneously in terms of the glazing / wall details – those relevant to this study are listed below.

A. General architectural appearance.

• Create an external appearance, particularlyfrom the west side, which does not draw too much attention to the building.

• Provide a consistency of architectural appearance to all elevations, whilst actuallydelivering very different functionalperformance for each.

• Complement the timber cladding by working to a modular size based on the gauge of the cladding board joint.

B. Light and energy performance.

• Remove unwanted intense high-level light and convert it into filtered light.

• Provide good quality views from the restaurant to the gardens.

• Satisfy Part L2A in terms of heat gain and heat loss.

C. Long term appearance and durability

• Provide durable, maintenance-free louvres.

• Ensure long-term durability of the timber.

• Minimise staining of timber from metal fixings and any other components.

• Ensure that louvres are of sufficient stiffness to prevent any sagging.

• Plan for fairly consistent weathering and greying of the timber and minimise raindrop staining from rain.

D. Manufacture and installation.

• Ensure that it is reasonably easy to erect the structures on site, probably by maximising the amount that could be prefabricated off site.

E. Maintenance and cleaning.

• Allow for easy periodic cleaning of glass.

Options considered

Option	Commentary
Using glass with louvred shading for the top gable section of all east and west gables	The Architect was initially keen to use the shaded glazing in the gables to achieve the desired visual effect from inside and outside. However, the cost of this was far greater than a solid wall and further thinking led to the conclusion that not every wall benefited from glass at high level. To maintain architectural consistency it was decided to use the louvres in a different capacity, namely as a rain screen cladding, allowing all elements to perform different functional goals, yet remaining architecturally consistent.
Construct the glazed curtain wall framework system using wood rather than aluminium.	The original designs were based on standard aluminium curtain walling details. It was decided that moving over to an entirely timber framed glazing system part way through the design process could not realistically be accommodated.
Use of aluminium louvres.	This was an obvious option given that the curtain walling was aluminium. However wood proved a better choice both technically and financially, mainly because creating bespoke solutions is much easier in wood.
Large gap between the curtain walling and fixed louvres to allow easy access for cleaning of the glass externally.	Cowper Griffith recognised that excessive slenderness could compromise the durability and stiffness of the louvres and therefore employed TRADA consultants to advise on this and other related matters. The steel framework system discussed above created an arrangement of three units in width, between the four uprights. Two and three panels per unit were considered with three being chosen. This was because: – With a shorter span it allowed more slender sections of louvre – The use of an odd number of panels, within an odd number of units (nine in total), created a more aesthetically pleasing symmetry.
Oak was initially considered because it had been used on the previous buildings.  Western red cedar was chosen.	At approximately 720kg/m3, oak is considerably denser than western red cedar at 390kg/m3. Whilst the higher density was not a problem for the cladding, it presented much greater challenges for the louvred panels in terms of being structurally supported by the curtain-walling framework.

Design detail chosen

Gable – steel framework

The slender and virtually non-visible steel framework, into which the timber louvred panels are seated, allowed the whole system to be supported back to the four aluminium structural upright members using only six fixings.

These were constructed by the curtain-walling sub-contractors and temporarily fixed to check for accuracy before being sent to Coulsons, the joinery sub-contractors. Working to the actual steel framework allowed Coulsons to make the timber panels to a precise fit within their workshop.

The steel framework simply comprised 6mm thick ‘L’ and ‘T’ sections, with a grey powder coat finish matching the aluminium to prevent staining of the timber from contact with the steel. To connect it to the aluminium members, simple cleats with bolt holes were welded to the back with similar partner members, secured via cut-outs in the cover caps, to the vertical aluminium structural supports. The framework can be removed reasonably easily if necessary, for example if replacement glass units are required.

The whole arrangement is set forward from the aluminium curtain walling by approximately 150mm. The aim was to:

• Provide sufficient space to install the components.

• Create two visually distinct entities in terms of the curtain walling and louvred panels.