Paul O’Carroll’s first job site was his father’s studio floor.

As a kid, he'd watch his father imagine buildings into existence from underneath the drafting table. "He'd take me on-site six months later. And I'd see this thing manifested into reality,” Paul said, "it was a magical and defining moment for me."

That spell for buildings never broke. But his awe of the design authoring tools did.

Years later, after self-teaching himself programming, finessing his game design skills, and starting a digital design studio, he asked a blunt question:

Why does AEC, the most collaborative industry in the world, still use single-player software?

Paul founded Arcol, a browser-based BIM tool that lets entire teams model and collaborate on buildings at once. He joined the Buildings 2.0 podcast to explain why realtime collaboration is both brutally hard and urgently needed.

The Single-Player Design Problem

Architects export. Engineers import. Contractors go on building on outdated information.

The global construction industry moves trillions of dollars a year. Yet the majority of AEC firms still shuttle large design files by email or shared drives. An 2018 industry study traced $280 billion of global rework to outdated data and siloed communication. 

Paul calls that waste “a software tax we keep paying,” arguing the tax ends only when everyone collaborates on one live model instead of ten stale ones. In one memorable instance, he recalls watching architects in his father's Dublin office emailing multi-gigabyte files across offices, with no success.

“So they loaded the files onto a hard drive … a big multi-million-euro project, and drove a USB drive three hours away to a contractor.

Fast forward, you now have tools like Google Docs and Figma. Each recognizing that people create collaboratively and in realtime, not in siloes.

In attempt to recreate this multi-player workflow, Paul built early collaboration software on top of existing design authoring platforms—only to realize collaboration is foundational, not a feature or a marketing checkbox.

Desktop-native software like Autodesk Revit will never be re-engineered for the browser. "You'll see Autodesk add on features like better data linkage so it doesn't feel like you're on the desktop—but you're still on the desktop," Paul advises. Revit's 1990s geometry kernel is fundamentally desktop bound.

And product newcomers like Autodesk Forma," he warns, isn't quite the realtime, browser-based design collaboration tool you'd expect. "I'd recommend you try Forma, it fucking sucks. The collaboration breaks the moment you use it," suggesting adding cloud viewers or data exchange layers can't turn a product into a real-time collaborative systems.

We don't believe collaboration is a checkbox. We believe collaboration is an incredible important part of the future of [the AEC] industry.

"Paul, this is an expensive problem to solve"

Live editing sounds simple. It isn't.

As Paul decides to close the digital design studio chapter, he doubles down on one of the most difficult problems in construction he believes requires a solution: realtime design collaboration on the browser.

At a crossroads, Paul's father advises him:

Paul, you do realize this is going to be an expensive problem. You're going to need at least $10 million.

"Dad, I'm going to need at least $100 million."

To start Arcol, Paul raised just over $5 million in pre-seed and seed capital from Cowboy Ventures, along with a string of high profile investors like Figma's CEO Dylan Field, Procore's CEO Tooey Courtemanche, former Autodesk's CEO Amar Hanspal, and Packy McCormick.

He hit the ground running, hiring Figma veterans to rewrite BIM fundamentals: conflict-free geometry, sub-second sync, granular undo.

The first line of code at Arcol had one goal: keep simultaneous edits from breaking the model. “We needed to start with conflict-free geometry,” he explains. That choice forced a clean slate.

Existing BIM files rely on a single owner; the moment two people touch the same wall, corruption risk appears. Arcol’s browser kernel—written from scratch—stores every change as an independent operation that can merge safely with any other.

“It’s easy to build a collaborative toy—really hard to build a professional app,” Paul warns. And even harder to refine for a performant experience. But when you hire a world-class team, the technical hurdles don't seem insurmountable.

And yet, it turns out it isn't the technical risk, but the go-to-market risk that causes Paul and the Arcol team pause.

When building a generational company with a multi-billion dollar vision, what part do you first start selling first?

Do you just take 10 years, raise $500 million, and try and build a full suite in the browser and then release it? Do you unveil a certain slice of it? What slice? How do you differentiate that?

The paradox of a collaborative platform lies on the one hand, designing for the various stakeholders around the table, but on the other, business pressure forces you to choose a stakeholder to go after first. Where do you start?

Feasibility is the foothold

Arcol’s road map doesn't begin with full-blown suite of products.

It starts with the earliest 30 days of a project, when owners ask Can this site work? and designers sketch massings and test-fits on tight deadlines.

Paul argues that this slice is where bad data first enters the pipeline; clear it here, and later stages inherit far fewer errors. His team chose the phase for several reasons.

First, it is universal: every project—office tower or tilt-up warehouse—runs a quick feasibility loop before spending real money.

Second, decisions in this window lock in most downstream cost; change a core now and you save weeks later.

Third, the workflow is still fragmented: SketchUp models, Excel budgets, emailed PDFs. By merging geometry, cost, and narrative in one live presentation canvas, Arcol replaces a daisy chain with a single link.

But the market for collaborative design tools is far bigger than we realize

Autodesk Revit is a ~$2 billion a year product line. But it doesn't monetize collaboration in the way it could.

As Figma has proven in graphic design: you build a design tool for designers. But the market isn't single-threaded. The roadmap expands into everyone working on that file—providing value for both the author and the collaborator.

It's biz dev, finance, sales, marketing, the client. And, at scale, you can monetize all of them.

Near term, Arcol is focused on building the best collaborative design tool with its success metric being adoption from designers, while also proving out usage from the collaborators around the table.

The future of design, empowered by AI Agents

Check out Paul O'Carroll's full Buildings 2.0 episode on Youtube or Spotify