Propelr — Real-Time Design Collaboration
A browser-based SaaS platform enabling 12,000+ architects and engineers to co-edit building plans in real-time with AI-powered compliance checking.
Overview
Status: client project. Client details are anonymised under NDA. This page documents the engineering approach and measurable outcomes.
An AEC (architecture, engineering, construction) startup needed a Figma-like collaborative platform purpose-built for building design — where multiple stakeholders could simultaneously edit floor plans, run structural simulations and verify building-code compliance without leaving the browser. We built the entire platform from a blank repository to a production SaaS serving 340 firms across North America and Europe.
Problem
Architecture firms were losing an average of 11 hours per project to version-control chaos — emailing DWG files, reconciling conflicting markups and manually cross-referencing local building codes. Existing tools were either desktop-only CAD software with no real-time collaboration, or generic whiteboard apps that lacked engineering precision. The startup needed a product that combined sub-millimetre drawing accuracy with Google Docs-style multiplayer editing.
Approach
We built a custom CRDT engine optimised for 2D vector geometry, allowing conflict-free concurrent editing with undo history across 50+ simultaneous cursors. The rendering layer uses WebGL 2.0 with level-of-detail streaming to handle plans with 500,000+ elements at 60fps. An AI compliance module trained on 2,800 international building codes automatically flags violations in real time as designers draw — covering fire egress, accessibility, structural setbacks and zoning. The platform runs as a Next.js application with edge-deployed WebSocket relay servers for <40ms collaboration latency worldwide.
Result
The platform launched with 340 paying firms and 12,000 active users. Average project turnaround time decreased by 37%. Code-compliance review cycles dropped from 3 weeks to 2 days. The AI module catches 94% of building-code violations before human review. The startup closed a $18M Series A within six months of launch, citing the platform's technical moat as the primary differentiator.
“They treated rendering precision and multiplayer sync as one problem instead of two. We went from a blank repository to a paying product without ever shipping a broken drawing.”
Tomas Lindberg
Co-founder & CTO · AEC software startup