Arnold House Primary School

• LAOCTION: NW8, London
• PROJECT: Extension at roof level
• CLIENT: Arnold House School
• ARCHITECT: Marianne Davys Architects
• STRUCTURAL ENGINEER: Heyne Tillett Steel
• QUANTITY SURVEYOR: Batey Associates
• CONTRATCOR: Newland Construction
• SPECIALIST GLASS CONTRATCOR: Cantifix
• CONSTRUCTION COST: £387,000 + VAT
• CONTRAT: JCT Minor Works Building Contract with Contractor Design
• DATE COMPLETED: 2013

Project Brief

The existing building is a primary school on a residential street in a conservation area of Westminster. The school is composed of two original houses, a link building and an extension to the rear with limited external play area.

The brief was to provide two new classrooms and two new practice rooms, and to identify where on the school premises the new accommodation could be located.

Project specifics

The original idea to build at roof level was developed with the school bursar, and then a feasibility study – including preliminary discussions with Westminster Council – was presented to the Board of Governors before the full project was commissioned.

The original roof was completely removed and the ceiling heights of the existing first-floor classrooms were reduced to gain headroom above. A new steel frame was built, with a flat roof and sloping pitches clad in the original roof tiles, so the appearance of the building on the front elevation was unaltered. The new classrooms are lit by dormers on the rear elevation, conservation roof lights on the side elevations and large roof lights on the flat roof, where solar panels that provide water heating are also located.

To obtain planning permission, it was necessary to convince planning that the corridor link to the rest of the school at eaves level was subservient to the original building. For this reason, frameless glazing was used and the new construction is well set back from the front elevation.

Project challenges

• There was a need to identify where on the school premises the new accommodation could be located.
• There was a need to obtain planning consent from Westminster to build at roof level in a conservation area with strict guidelines controlling what was considered acceptable.
• There was a need to build above the existing school within a short construction period with a fixed completion date, and for part of the project to be undertaken during term time.
• The frameless glass extension required a road closure and a crane to lift the glazing, as well as a very accurate survey and drawings, and a skilled specialist team on site.