Re: Fencing/unremovable cielings

@simonrowland88 It sounds like what you want is a yard fence  - no floor/foundation/ceiling. To create this just begin the fence at a point that is at least one tile away from the home/foundation. 
This way it will not add the foundation. No need to build a room for yard fencing. When you finish the fence go ahead and connect it to the home if you want... draw the fence (fence tool) moving toward the home, not beginning at the home. It will join to the home and not have a foundation. Please see this article for illustrations of what I mean: https://simsvip.com/the-sims-4-building-guide/#Fence

You asked about deleting ceilings. This should not be an issue once you remove the unwanted room around the yard and draw the fence as stated above, but for future reference:

• To delete floors click on the floor to get an option 'remove floor'. 
• To delete ceilings, click on the room/wall so the room is highlighted. click on the yellow rim at the top of the room/wall. It should then give you the option ot delete the ceiling.

Hope this helps. Please let us know if you need further clarification. Thanks!