Without an attic ladder or set of stairs, a home’s attic usually has untapped potential. Homeowners know it’s up there, but it’s a hassle to access for storage, much less use as a living space.

A do-it-yourselfer with average skills can install pull-down stairs for an attic. There are tricky parts to the project, however, and it takes careful planning. You will need a helper, and you should ...