Architecture and Engineering Firms: Sharing Large CAD, BIM Files

Why large CAD and BIM files strain normal cloud storage

Cloud sync works well for Word files and PDFs. CAD and BIM workflows differ in three ways: files are big, projects contain huge numbers of small files (xrefs, families, plot sets), and several people may write to the same model at once. Each of these hits a different limit.

Microsoft's restrictions and limitations page recommends syncing no more than 300,000 items in total, with a higher limit only on well-specified PCs. A practice with ten years of projects can pass that quickly. Google's shared drive limits allow files up to 5 TB but cap each user at 750 GB of uploads in 24 hours, which matters during migration.

Revit and live models: don't use synced folders for worksharing

Autodesk's support article on using Revit files on Dropbox, Box or OneDrive answers directly: if you expect file-based worksharing to behave as it does on a local network, the answer is no. Sync tools copy whole files in the background and don't understand Revit's central and local model locking, which risks conflicts and corrupted models.

• Local file server or NAS: central models on the office network, the traditional set-up for file-based worksharing.
• Autodesk cloud worksharing: Revit Cloud Worksharing through Autodesk's BIM Collaborate Pro subscription, built for distributed teams.
• Single-user models: a model only one person edits at a time can live in SharePoint, as long as people don't open it simultaneously.

AutoCAD drawings with xrefs behave better in sync tools, but keep relative paths and avoid very deep folder structures, because long file paths can fail to sync.

NAS, cloud or hybrid: which set-up fits a small firm

Our SharePoint vs OneDrive guide explains how to structure company files in Microsoft 365, and our Synology NAS vs cloud backup guide compares the backup side. As an example of off-site storage cost, Backblaze B2 lists US$6.95 per TB a month on its pricing page (approximate, as of October 2026).

Sharing with consultants and clients safely

Structural, M&E and QS consultants, contractors and clients all need files, but each only for their projects. The common mistake is giving them a login to the whole drive or a never-expiring link to the project root.

1. 1

   Create a per-project external folder

   Make an "Issued" or "Exchange" folder for each project. Share only that folder, not the working folders.

2. 2

   Share with named people, not "anyone with the link"

   Use specific-people links or guest accounts tied to the consultant's email, so access can be reviewed and removed.

3. 3

   Set expiry dates

   End access at project completion or after a set period. Renew if the project runs longer.

4. 4

   Use upload requests for incoming files

   Let consultants drop files into a request folder instead of emailing large attachments.

5. 5

   Review external access every quarter

   List who outside the firm can reach what, and remove anyone whose project has closed.

Versions, ransomware and project archives

Design files are the firm's main asset, and ransomware targets exactly that. Sync tools copy encrypted files to the cloud just as faithfully as good ones, so sync is not a backup.

How long to keep closed projects depends on your contracts, insurance and professional obligations, so agree it with the partners and your adviser. For architects, our BOA rules website guide covers the professional side of your public presence.

Do it yourself or get help?

A small practice can tidy external sharing and turn on version history itself in an afternoon. Designing a hybrid NAS and cloud set-up, migrating years of projects without breaking xref paths, and setting up immutable backups are worth getting right the first time.

Our Backup & Ransomware Recovery (S$290) sets up off-site, immutable backups of your NAS and cloud files and tests a restore. Microsoft 365 / Google Security Lockdown (S$590) sets sharing defaults, guest access rules and MFA so consultant access stays controlled.