From ISDN to VoIP: Architecture Firm Goes to The Cloud

This north London architecture practice has been shaping residential and mixed-use spaces for over 30 years, with a particular focus on regenerating brownfield sites and transforming overlooked urban spaces into something new.

With a growing team and a busy portfolio, communication is critical. Whether collaborating across projects, coordinating with planners, or connecting with clients, the firm relies on clear, consistent lines of communication to keep work moving.

As they looked to the future, and towards a planned office move, they knew their telephony setup would need to evolve with them.

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Industry: Architecture

Organisation Size: 50-100 employees

Service Areas: VoIP Telephony

Like many businesses in the UK, the firm had relied on ISDN lines for years, a legacy telephony solution that once served them well, but was quickly becoming outdated. With BT announcing plans to phase out ISDN by 2025, the clock was ticking on finding a better alternative.

The limitations were already clear. Every change, from adding a new line to expanding the system, meant delays, engineer visits, and extra costs. As the firm grew, and remote working became part of everyday operations, the cracks in their existing setup began to widen.

Calls could only be answered on-site. There was no easy way for remote staff to stay connected, no flexible routing options, and no modern features like voicemail-to-email or call analytics. For a business with evolving needs and a mobile workforce, the existing system was holding them back.

The team needed something future-proof; a cloud-based solution that could scale with them, support remote work, and eliminate the operational friction of outdated infrastructure.

To give the firm a seamless, modern telephony system that could grow with the business, we designed and deployed a fully cloud-hosted VoIP solution, tailored to their team, workflows, and upcoming plans for expansion.

Here’s what the process involved:

• Migrated all telephone numbers, including primary lines and individual Direct Dial-Ins (DDIs), from BT to a trusted VoIP provider, ensuring no disruption to service.
• Ran collaborative brainstorming sessions with internal teams to design the ideal call flow: from receptionist routing to in-hours and out-of-hours messaging, and voicemail handling.
• Configured physical handsets for reception, meeting rooms, and key team members, while also equipping remote employees with VoIP desktop apps for laptops and mobile devices.
• Deployed a solution that would allow flexible call handling, centralised management, and scalable setup, ready to adjust as the team grows or relocates.

With their VoIP migration complete, the firm now benefits from a fully cloud-hosted telephony solution that fits the way they work: flexible, remote-ready, and scalable.

• Remote employees can now make and receive calls from anywhere, using desktop apps or mobile devices: no more being tied to physical handsets.
• The system scales effortlessly: as new team members join or the business expands, new users can be added in minutes without expensive infrastructure upgrades.
• A suite of modern features, including personalised voicemail, voicemail-to-email, call routing, and out-of-hours messaging, gives staff more control and improves responsiveness.
• With an office move on the horizon, the firm won’t face downtime or delays: the VoIP setup will move with them, without the hassle of reinstalling phone lines or waiting on telecoms providers.
• The old equipment was responsibly decommissioned and recycled via a green-certified partner, closing the loop sustainably.

The result? A communications system that’s as forward-looking and flexible as the architecture firm itself.