To delete one of the walls of the room you need to tap on it first.

Then use the Hide button. That way the wall will no longer be visible on your plan. But if you want to get it back, use the same algorithm: pick the wall and click Unhide icon.

Or you can also delete the wall by selecting the dot of the wall and dragging it to the other dot. This will "delete" the wall and merge two dots.

Did this answer your question?