it's not easy to try and come up to an explanation taking that part out of context.
as you might have noticed, nether novas deals with the ambiguity of a choice on whether to stay and settle down, or continue on as in a quest for something. this is expressed throughout the song with recurring metaphors, such as the house one that appears in your snippet.
in those particular lines i think the possibility of maintaining individuality and privacy in situations of intense sharing is discussed, and rejected (see also the beginning of on your time). to paraphrase - without adding too much of an interpretation, though - : even if we are told that there is a chance to find our place in rational, ordered environments such as families, as soon as someone insomuch as expresses feelings, the divide is crossed and our intimacy is violated; trying to create more space for us only results in seeing the space (it should read "the room that you furnished and graced", btw) that others have already imagined and that therefore belongs to them more than to us: the smallest sharing/closeness, is enough to drown our own private world and dissipate individuality completely.
