Modular vs Container vs Traditional Granny Flat: Pros, Cons and Build Times

With three main construction methods available for granny flats, understanding the pros, cons, and timelines of each helps you make the right choice.

Modular (Factory-Built)

Built in a factory and craned onto your site. Pros: fastest build time (8–12 weeks total), weather-independent construction, consistent quality. Cons: limited customisation, crane access needed, transport costs for distant sites.

Container Conversion

A shipping container fitted out as a dwelling. Pros: unique aesthetic, shell already exists, can be relocatable. Cons: insulation challenges, steel cutting costs, potential council resistance, limited width (2.4m internal).

Traditional Construction

Built on-site from scratch. Pros: maximum customisation, familiar to all trades, well-understood by councils. Cons: longest build time (16–24 weeks), weather-dependent, potentially higher labour costs.