Granny Flat or In-Law Suite? Which is More Prudent?

Granny flat built above a garageThis accessory dwelling unit, or granny flat, is in Bainbridge Island, Wash. Zoning laws here dictate that ADUs are accessories of larger residences with no more than 800 square feet of finished living space. Image: Coates Design

If you need to house aging parents or adult children, or if your family is multi-generational, what’s better — an in-law suite or a little granny cottage in the back yard?

If you need to house aging parents or adult children, or if your family is multi-generational, what’s better — an in-law suite or a little granny cottage in the back yard?

Our data says you’ll spend less remodeling the basement or adding an in-law suite to your attic. But a USA Today feature suggests you consider building a small house or cottage in the back yard.

For instance, the article notes that in Vancouver, detached cottages or “laneway houses” have become popular: “[Architect James Tuer] … designed several, including one that cost $200,000 and rents for about $1,600 monthly. He says the owners have aging parents who may live there, or they may use it themselves at some point and rent out their main house.”

A Seattle builder is also building backyard cottages in the neighborhood of 800 square feet and at a cost of about $125,000.

Building a second house on your property means a trip through the zoning process versus the much simpler permit process you follow when you remodel existing square footage.

And if you don’t live in a trend-setting metropolis, zoning rules will likely keep you from building a second house on your lot unless you physically attach it to your existing house and put a family member in it rather than a renter. If that’s the case for you, maybe grandpa or the kids can make do with an apartment in the space over the garage.

How are you accommodating in-laws, grown kids, or renters in your home?