With site ownership being pushed out to Information Workers across our organizations for Office 365 Groups they’re an owner of, my tendency as an IT Pro is to try and put some controls around it. I want this simply to mitigate some of the risks of having users with minimal SharePoint experience and training having full reign over a site. Controls come in many forms: security controls, data protection controls, retention controls, etc. and there are numerous tools within Office 365 to implement those. One simple control I think is required is preventing a Group owner from creating a subsite in their (Group) site collection. This governance control would support the flat site architecture SharePoint model – a good thing.
Yesterday, I learned about a setting to do just that in the classic SharePoint Admin Center from fellow MVP, Dave Feldman (@BostonMusicDave). I have no idea if this setting is new or not, but I can only assume there are 1 or 2 others out there who, like me, didn’t know it existed but could benefit from knowing.
The setting will hide the subsite menu in Site Contents for Office 365 Group owners. (image)

Why do I like this setting? It supports the flat site architecture model where every new site provisioned is a site collection and not a subsite. A flat architecture will serve organizations well over time. Check out my blog post, Advantages of a Flat SharePoint Site Architecture, where I discuss in more detail the advantages of having one.
Here’s what the New link looks like for a Group Owner before and after the change:
If you’re trying to stay in a flat architecture and want to prevent any subsites from being created in an Office 365 Group site, turn this setting on! When you navigate to the Subsites section of Site Content, this is what you want to see… 🙂
Thanks for reading.
-JCK
Until you hit the 500k site collection that is… there is still room for subsites in a large org, especially since lots of other workloads (Teams, Yammer etc) end up creating site collections that all count towards the limit. A 250k size user base with a 10 year retention policy will eat that capacity pretty fast.
Agreed. There are always organizations that will hit those boundaries. I would say in those orgs, there needs to be what I call a “controlled sprawl” with some automation and governance in place rather than letting site owners go at it creating subsites “at will”. Either way, it requires someone with experience to know how to avoid hitting that 500,000 wall. (like yourself it sounds like) 🙂
-JCK
We’ve enabled this recently. Wish we would’ve done this when we turned on self-service. Better late than never. Would love to see the same control for a Comm site.
Hi Kerry! Awesome! Agreed, it’s better late than never… I’m not sure why the distinction was made for Comm sites. With the SharePoint Hub, the notion of subsites seems even less appealing unless you’re in an org that will run into the site collection limit. I don’t know of any orgs in that boat, but I’ve been told they’re out there. Either way, i think we agree it’ll require governance if subsite provisioning isn’t stopped. 🙂
-JCK