Complicated Office Conversion Using PD

This building was originally an office block with three buildings. The site was occupied by a four storey (Gate 2) and a three storey (Gate 3) office block. Both buildings were elevated from the ground to form a vast car park. The partial footprint of the third block (Gate 1) – that had burned down – was still evident on the site too.

Granit was initially asked to tackle this complicated office conversion using PD (permitted development) to convert the existing office buildings into flats. Consequently to submit an application for external treatments to upgrade the thermal performance, to introduce balconies and privacy screens and new entrances to the buildings. Additionally there was a requirement to design a scheme to add extra residential units to the site.

Key Challenges 

Challenges that had to be overcome during this project include:

  • PD application: using the roof space of both buildings to create duplex apartments at the top level.
  • New builds application: relating the new builds to the existing context, considering the site constraints; the new build application also had to meet the London Space Standards.
  • Noise issue, given the proximity of the building to the railway.
  • The site is restricted on the western side by the railway line connecting Horsham to London.

Selection Criteria

An architects practice with demonstrable experience and knowledge of the following was required:

  • Experience of working with the local planning authority
  • Experience of Construction Design and Management including leading a team of constructors onsite

The Solution 

Granit provided guidance on this residential development scheme which included:

  • PD application: advising on the number of extra units which could be added to the site and how best to arrange them in order to achieve the highest ROI
  • New builds application: providing detailed layouts of each unit onsite
  • Full technical package: building compliance testing was carried out
  • Upgrading the original facade and ensuring it was in keeping with building regulation, Part L
  • Part of the undercroft area has been used to create gym facilities, while refuse and cycle stores have been implemented

The Results

Upon completion of this project key results included:

  • Production of a tender package issued to building contractors which included:
  • General arrangement plans, elevation and sections
  • Service drawings including indication of lift and stair core layouts
  • Bathroom and kitchen layouts
  • Doors, windows and roof lights specs
  • Detailed drawings of thermal and acoustic upgrade and fire protection
  • PD application for change of use is now lawful
  • The other applications are still ongoing

You can download the case study by clicking here.


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