@trrx1enx3ig9
There are a couple of things you can try to save the house intact or at least save the structure and the house contents separately. In build mode, you can try saving the house to your Library and then replacing the one in the game with the copy. Then move the sims back in. The downside is that the sims will lose connection with all the personal items and collectibles. You can reconnect with the collectibles by dropping them in a sim inventory and then putting them back where they were. For things like diplomas etc., you do lose the connection permanently. Some may still show who they belong to though.
The other way you can try is when you move the sims out, keep the furniture. Then move the sims back in. This way, you don't lose the connections to the collectibles and personal items, but you'll have to refurnish the lot. Everything you had will be in the household inventory, so it is a matter of just placing all the items back where they were. It will take you a bit of time to do that.
Hope this helps.