Likely because you need to hire a structural engineer to sign off on the project. Building codes allow us to do this sort of thing without direct engineering i

Likely because you need to hire a structural engineer to sign off on the project. Building codes allow us to do this sort of thing without direct engineering input and most municipalities have not adopted a code that define safe practices for this sort of construction. Additionally, materials selection and availability is geared towards stick frame construction and you may not have everything you need from big box hardware stores or local supply houses.