Why is it that putting up the framework makes the floor area of a house look smaller than it is? Now, I know the house can’t actually be that small because it takes up a huge chunk of the site, it just appears that way. So I asked a friend – Google, and found out that this is a common optical illusion that has many people freaking out over. One of the forum sites said that the illusion was due to comparing the outdoor space with that inside the house, it was also recommended that people didn’t visit the site too often when the build was going on – obviously most people don’t live next door to their build site.