Each has its own pros and cons. Site-built ADUs use traditional stick-built construction. While more expensive than factory-built ADUs, site-built ADUs may command higher resale prices. Construction of site-built ADUs can also be slowed down by weather. Factory-built ADUs save money and allow you to bypass many delays due to poor weather. Construction time on-site is lessened. But factory-built ADUs may require crane rental costs and difficulties with moving large pieces to the site.