SE increased the size of the housing a few patches back but the issue is the following:
Garden only allows for 50 items wich is maxed easily if you form a stair to get on the house roof or balcony. Plz add at least 10 more slots.
Interior has an issue too. Right now Mansions are maxed at 400 items. But we recently decided to use the lower room for a maze and decorator event, but I'm allready at 400 and I would still need to play like 50 items to make everything look good. I would recommend SE adds 25 extra slots for the small house, 50 extra slots for the medium house and 100 for the large house.