Anyone tried this? I haven’t yet but will be having a closer look soon. Gliffy is a browser-based tool for creating and sharing diagrams. It also allows for collaboration. In theory you can:

Create many types of diagrams such as Flowcharts, UI wireframes, Floor plans, Network diagrams, UML diagrams, or any other simple drawing or diagram

According to edtechpost it’s incredibly easy to use…

Update: have tried it now and yes very easy and def worth a look.  This floorplan took two mins.  You can export to various formats including PNG