Is this a matter for Tech Support or can someone on the forums tell me...

[Katalyst777]

So you ARE using a bunch of vertical lines. Try setting those wall layers to either solid or transparent and see if that offers any improvement. What about fill styles for other things like that yellowish looking room in your screenshot? Maybe do a File> Save As to make a copy of your plan and get rid of all the fill styles in your wall types, rooms, terrain objects, etc, and see if your time improves.

[Keith_K]

I'll give your suggestion a try in the morning, thanks. I'm off to bed now.

The yellowish looking room is depicting gravel in the courtyard formed by the five dwellings. It's the erm..."best" colour I could come up with from the limited choice available.