A steel-clad roof extension – which has been entered into this year’s AJ Small Projects Awards – boldly reworks the ’loft conversion’ aesthetic
This extension in Walthamstow, north London, designed by deDraft architects, is designed to naturally weather and darken in tone, blending into its surroundings of red concrete tiles over time. Designed for a young family, the extension provides a master bedroom, en-suite bathroom, storage space and sheltered terrace with 25m² of extra space at the cost of £60,000.
Each steel panel of the weathering-steel cladding has been folded, installed and adjusted to achieve tight, sharp joints before being finally reinstalled and bonded to a lightweight timber sub-frame.
Dedraft da residence © whitaker studio 011
Source: whitaker studio
Given the small-scale build, initially sourcing either a metal cladding specialist or metalworker took several months longer than expected with many unwilling to commit resources to a small and challenging fabrication. The selected metalworker, although not familiar with external cladding work (or indeed Cor-ten) offered invaluable propositions and solutions to drive the process.
Our key priority was to eliminate any visible mechanical fixings and avoid the appearance of standardised cladding panels. After much discussion the solution was to fabricate a series of 3mm-thick sheets of weathering steel bonded to a ventilated timber sub-frame, therefore reducing any imperfections that arise from a welded ‘rail and bracket’ system.
Dedraft da residence © whitaker studio 001
Source: whitaker studio
The use of a 3D Rhino model addressed the initial complex geometry of the tight, chamfered soffits and reveals, enabling the builder to set out the structural framing of the inverted dormer while factoring-in details to facilitate the cold-roof ventilation requirements, planning limitations, concealed fixings for window/door frames, frameless glass balustrade and the integrated roof drainage.
In order to negate the need for a competitive tender and allow a quick commencement of the build, a local, experienced and design-minded builder was lined up.
Dedraft da residence © whitaker studio 002
Source: whitaker studio
This intense period of meticulously detailed setting out proved highly beneficial with the raw, unweathered steel panels being cut and site tested, eliminating complex junctions and over-tolerances that would have undermined the seamless aesthetic. Upon initial installation, the cladding was raw, natural steel and with increasing exposure has weathered to a much darker, burnished appearance complementing the aesthetic of the original property.
Overall the undertaking of this residential project demonstrated the need for a tight collaboration required between builder, metalworker, ourselves and an engaged client – who patiently lived in the project throughout the duration of the build! A joy to collaborate on.
Grant Straghan, practice director, deDraft
Start on site March 2017
Ccompletion July 2017
Gross internal floor area 95m² total / 25m² extension
Gross (internal + external) floor area 114m²
Form of contract or procurement route JCT Building
Construction cost £60,000 incl. VAT
Construction cost per m² £2,400 incl. VAT
Structural engineer Structures Made Easy
CDM coordinator ACT Surveyors
Approved building inspector ACT Surveyors
Main contractor BWP Ltd
CAD software used AutoCAD 2015, Rhino
3095989 3088872 ajspad2018v3p4p
How to enter AJ Small Projects
- Head to the AJ Small Projects Awards website, register and pay your entry fee
- An email will then be sent to you with log in details for the AJ Buildings Library
- Upload your project to the AJ Buildings Library. You will need to provide:
- A 150-300 word text describing your project
- At least eight photographs, five drawings and one working detail to illustrate your project. NB Images should be high resolution and you must be able to give us third-party reproduction rights (for publication in the AJ, AJ Buildings Library and distribution to other publications to promote the awards)
- Project details including name of practice, name of project, date of completion, total cost, gross internal floor area, client, structural engineer, services engineer, quantity surveyor, main contractor, and other subcontractors and suppliers
- Entries must have been completed between 1 January 2016 and 31 December 2017
- All entries must have a maximum total contract value of £250,000
- Projects must not have had significant coverage in the architectural press (if your project has been covered elsewhere, please declare where)
- Projects must be located in the UK or built by a UK-based practice abroad
- All entries will be displayed in the AJ Buildings Library
2 February 2018