Do all the houses you build look the same?

Solution 1:

The three Hearthfire construction properties, with regards to the house, are identical.

However, each of the site have a single unique property:

Heljarchen Hall: grain mill

Lakeview Manor: apiary

Windstad Manor: fish hatchery

They also have different outdoor mining spots for clay and stone.

I've always picked Windstad Manor for the fish hatchery because fishes can give you amazing potions, and it is a reliable source of salmon roe.

Solution 2:

Yea the houses all look the same including the interior designs, but it will look different on the outside depending on what addition you want to give it, but each additional structure will look the same as well.