Birmingham Library facade by Mecanoo
A technical look at the distinctive facade Mecanoo designed for the new Birmingham Library.
Centenary Square, Birmingham
Gasometers, tunnels, canals and viaducts characterise the landscape of Birmingham and its surrounding area. These landmarks of the city’s industrial past, which fuelled its growth, informed the intricate, circular design of the cladding for the new Library of Birmingham, claims the building’s Dutch architect Mecanoo.
The Delft-based practice won the international competition to design the library in August 2008. It will controversially replace John Madin’s 1974 library in nearby Paradise Circus.
Since the project received planning permission in November 2009, it has undergone some modification. But one crucial element that hasn’t changed is the building’s outer envelope, a striking filigree of overlapping metal rings that wraps around the building starting from first floor and extending up to the eighth floor of the 10-storey structure.
The outer frieze is composed of two different sized aluminium circles which will be fixed to an envelope of double-glazed curtain walling.
The £189 million building extends from a children’s library at lower-ground floor level to a gold anodised rotunda at the top, which will house the wood-panelled Shakespeare Memorial Room. The library has two external terraces, a full-width 12m-deep terrace at third floor level and another terrace at seventh floor level.
The building is sandwiched between Baskerville House, built in 1938, and the 1971 Birmingham Repertory Theatre, with which it will connect at ground level, sharing an entrance and foyer, café/ restaurant and a new flexible studio theatre. The three buildings front onto Centenary square and, says Francine Houben, Mecanoo’s founding partner, “will reflect the changing architectural expression through the years” becoming one of three “palazzos”.
Construction began in January 2010 and the in-situ post-tensioned concrete structure is well under way. The structure was originally going to be in steel, but this was superseded by post-tensioned concrete because it produces thinner floor slabs, resulting in a lower building, a key requirement of the planners.
The cost of the total envelope, which includes renovations to the facade of the Repertory Theatre, is £14 million.
Cast iron was briefly considered for the intricate frieze that wraps around the library, but was ruled out in favour of aluminium, which is cheaper and lighter, so reducing loading requirements for the main structure. Aluminium also lends itself to extrusion manufacturing.
The frieze is comprised of two sizes of circles – 5.4m-diameter, powder-coated black discs provides the frieze’s structure. Attached to these are 1.8m-diameter circles, powder-coated silver.
The manufacturing process involves cutting and curving 3mm-thick extruded rectangular box sections before machining, drilling and cutting.
The frieze elements are manufactured in Germany. They will be assembled in two halves and joined together on site.
A bespoke steel dead load bracket will be bolted to the top prior to it being craned into position. This bracket is designed to take the entire weight of the frieze element as it is cantilevered 900mm away from the glazed facade.
The element will then be hoisted by crane and installed onto a number of small circular steel restraint rods, also powder-coated, which brace the frieze back to the facade and limit deflection under wind load.
Curtain wall system
An aluminium-framed, black powder coated curtain wall system will be hung 900mm behind the outer envelope of aluminium circles. The 1.8m-wide double-glazed panels will vary in height form 4.5m to 6m, and will hang from brackets at the top and interlock together.
A 1.5m-high louvred section will define the top and bottom of each panel and run the full width of each storey from first to seventh floor. The powder-coated aluminium louvres allow natural ventilation.
The louvres will allow fresh air into the ceiling plenum when the damper box opens. The box, which is connected to the inside of the facade above the suspended ceiling, will be connected to the building management system that monitors temperatures both inside and out.
Where the acoustic load on the facade is high, a solid insulated panel (200mm thick) will be installed behind the louvres. The aim is to achieve a U-value of 0.5W/m2K to this part of the facade, helping the building achieve a Breeam “excellent” rating.
The library’s ground level and the link to the adjacent theatre will have a 7.5m-tall, steel-framed, double-glazed facade. The bays will be 1.8m wide and one continuous transom at 2.9m above the finished floor level will transfer the wind load to the concrete columns behind. The steel frame will consist of laser welded steel box sections spaced every 3.6m and T-sections located in between the box sections.
The south (front), east and north elevations of the ground level are fully transparent, to let the public see the facilities and draw them into the building.
Cladding to Archive & Heritage floors
The cladding at levels five and six requires a different system since these floors will house more than 6,000 archival collections, which require a climatically controlled environment.
The two levels will have tall floor to ceiling heights – level five is 5.9m tall and level six is 4.7m tall. To achieve the demanding U-value of 0.12 W/m2K, two layers of high performance insulation of 330mm mineral wool and a 150mm steel faced composite panel will sit behind a gold-coloured, anodised, unitised rainscreen system. This is comprised of 1.8m-wide by 6.6m-high panels.
The external frieze clads the aluminium rainscreen revealing a golden glow from within.
1 Large circles: 5400mm diameter, aluminium box section 150 x 75 x 3mm, black powder coat
2 Small circles:1800mm diameter, aluminium box section 80 x 40 x 3mm, silver powder coat
3 Wind restraints
4 Spigot junction
5 Dead load bracket
6 Gold coloured anodised aluminium rain screen 3mm thick
7 330mm-thick thermal insulation, Rockwool rain screen Duo-slab
8 High performance double glazing
9 Trench heater
10 Raised access floors
11 Post tension concrete floor slab
12 150mm-thick Durawall 120 panel
13 Level 6 Archive & Heritage stores
14 Level 7
Crowning the top of the library will be a gold-coloured rotunda. The 8.5m tall space is 17m in diameter and features a 15m-wide indoor terrace created from seven panels of 1.2m tall and 3m wide curved panels of gold-coloured aluminium rainscreen that will be hung and screw-fixed to an aluminium frame.
A wood-panelled room, originally designed by John Henry Chamberlain and built in 1882 to house the Birmingham Shakespeare Library, will be dismantled, labelled and relocated to the rotunda. The panelling is currently in the John Madin designed library and when erected in its new location will be called the Shakespeare Memorial Room.
The room will be accessible to the public by appointment only, but the indoor terrace offering panoramic views of the city will be accessible by lift during opening times.
Client Birmingham City Council, Architect Mecanoo Architecten, Construction partner Carillion, Facade contractor Lindner Facades, Structural engineer Buro Happold, Project manager Capita Symonds