JM Architects

The Crown Estate

Morgan Sindall

Scope & Products:

  • Heritage Steel Thermally Broken Windows
  • Manufacture of Bespoke Aluminium Extrusion to Picture Frame Windows
  • Bronze Patinated Panelling to Canopy


  • Very demanding specifications and tolerances requiring assiduous attention to detail by our design team
  • Development and manufacture of Dies Casts to allow us to extrude bespoke aluminium to match the existing window transoms and picture frame surround.
  • Bespoke extrusion for picture frame of window to match previous windows
  • Sightlines maintained for planning but requirement of increased high thermal performance system
  • Bespoke lattice work design to glass and framing system
  • Logistically challenging site constraints within a highly sensitive neighbourhood
  • BREEAM Excellence requirement.


The external façade had very stringent design constraints in to ensure that the Westminster planning requirements were fulfilled.  For this reason the project required a competent design led partner that not only understood the requirements but also had the facilities and previous experience to deliver the quality of product that is required when working on some of London’s largest and most prestigious buildings.

Employed by the main contractor, Morgan Sindall, Propak worked on the early stages of design, to come up with solutions to meet planning requirements and architectural intent.

Propak designed and developed a bespoke variation to the Janisol Arte framing system, to ensure the highest thermal performance, and integrated custom made aluminium extrusion and t-sections to the exterior of the frame and glass to mimic the outdated Crittall style windows.

The project is a contender for a BREEAM Award 2015, a high-profile annual event which celebrates excellence in sustainability, representing the most innovative projects and a variety of inspirational buildings from all regions of the UK and several European countries including the Czech Republic, France, Norway, Romania and Sweden.

It was commented on many occasions that this variation of our Heritage window system is by far and away the most impressive that has been seen on the market for many, many years.

Project Gallery: