Wednesday23 August 2017

Cottrell & Vermeulen’s Brentwood School

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Brick is used to clad a new sixth-form centre and assembly hall for Brentwood School in Essex.

When Cottrell & Vermeulen Architecture was asked to design a new sixth-form centre and assembly hall at Brentwood School, it was only natural that the practice turned to brick as the key envelope material. For this is a site awash with substantial brick buildings such as the 16th century Old Big School and Otway House, a once fine 19th century building and former vicarage in need of extensive repairs.

“There are a lot of brick buildings and polychromatic brick patterns,” says project architect Jonathan Dawes. ’It was the catalyst for us to think of something that fitted in with what’s there but also gave a new identity for the sixth form.”

The practice is now halfway through construction of the scheme, which consists of two new builds on either side of Otway House. All three buildings will be interlinked to form an impressive trio of new accommodation on a scale in keeping with other key buildings along Ingrave Road such as the civic offices and the Roman Catholic Brentwood Cathedral, designed by Quinlan Terry. To the north, the sixth form teaching block of 16 classrooms rises three storeys. On the other side of Otway House is the triple-height assembly hall, with its distinctive repeated gables, designed to hold 400 people.

Cottrell & Vermeulen had initially intended to demolish Otway House but this was rejected by planners, mindful of the area’s conservation area status. The final design creates a new social and study area “home base” for sixth formers within the retained 1876 facade. This is being restored with the help of specialist brick company Lambs Terracotta, which is repairing and recreating details such as the shingle-effect voussoirs above the windows and the arched windows. Some details, such as the terracotta window mullions, are too damaged and are being replaced instead. Internally, the building is being extensively reworked and will retain just “memories” of the original spaces, with links to both the new buildings.

For the two new-build blocks the architects have specified Ibstock bricks and came up with a number of different patterns in plane and relief to give a crafted, bespoke solution. Working with contractor Hutton Construction and Global Brickwork, Cottrell & Vermeulen created a number of test panels for the bricklayers to follow.

The project was temporarily delayed when Japanese knotweed was discovered on the site but the buildings are now on course for completion next spring. The new facilities will support students undertaking the International Baccalaureate curriculum, which has been recently introduced at the school.

Classroom block facade

A load-bearing masonry construction of blockwork and brickwork is used with the Omnia system of pre-cast panels and a poured concrete slab. These form the floor slab and internal wall finish to give the thermal mass needed to maintain the constant temperature suitable for teaching conditions. Bricks are tied to the masonry with a 130mm cavity in between. To tackle the problem of noise from the nearby busy road, acoustically attenuated air vents are incorporated into 450mm window reveals that allow in air but not sound. Three chimneys – one single, one double and one quadruple – pull air up through the building and out.

With the aid of plenty of paper models, the architects came up with a complicated “diaper” diamond brick pattern for the facade that refers to the decorative brick on other nearby buildings. The patterns are created in header bond using Heritage Red as the main brick and Beven Dark as the contrasting, much darker element.

At ground floor level, the pattern is quite lacy but at upper levels it becomes much bolder, terminating in barber pole twists on the chimneys. On the north-east corner closest to the main street there is a contrasting pattern of small flowers executed with the Bevens as the background and the Heritage Red as the highlight.

The roof is covered in Keymer hand-made terracotta tiles to tone in with the brick elevation. To assist the team of a dozen bricklayers, the architects produced copious setting out drawings and reference panels to indicate exactly how the pattern is created.

Assembly hall pattern

Both relief and flat patterns are used on the assembly hall elevations, which feature a skin of bricks on the steel framed building, which is lit by six rooflights.

At plinth level, the pattern is an inverted diaper of snapped head Flemish bond half a brick thick (header/stretcher/header/stretcher) with a bolder diamond pattern in relief on the gable created in headers. This serves to accentuate the geometry of the gables.

The relief pattern is formed by three lengths of solid bricks – 159mm, 187mm and 215mm – arranged to create the pattern in a contrasting header and stretcher bond. The headers are used for the infills and the stretchers for the relief. The bricks had to be solid rather than frogged to avoid water penetration. The brow of the gable is formed by 450mm wide coping. Special mortars were mixed to match the brick.

Elsewhere on the building, there are some variations, created in collaboration with Ibstock’s Kevington subsidiary. On the plinth, bonded specials are used to turn the corners and on the plant room, extra ventilation is provided by forming a grille in the diaper pattern.

Project team

Architect Cottrell & Vermeulen Architecture, Client Brentwood School, Structural engineer Engineers HRW, Building services engineer Max Fordham, Quantity surveyor Stockdale Consulting, Main contractor Hutton Construction, Brickwork subcontractor Global Brickwork, Bricks & fireborne capping supplier Ibstock, Brick-faced lintels Kevington, Mortar Cemex


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