How big is a 3 story house plan? They can have as little as 1470 square feet of living space. All the way up to 5507 square feet of living space. We offer a collection of unique 3 story house plans to choose from. Some of these 3 story house plans come with an elevator, like the Lilliput plan. Most of our plans have open, airy and casual layouts that complement the relaxed living that is desired in such Three-Story styled homes. If you are looking for a 3 story house plans with a garage underneath, we have several. The Casa Bella has 1967 square feet of living space, 3 bedrooms and 2 baths, with a garage underneath. The perfect home for a small lot, or waterfront setting. All our modern 3 story home plans incorporate sustainable design features to ensure maintenance free living.