Building a custom house requires you to pay 15-30% more. Then, there is the significantly longer time frame necessary to build a custom house from scratch. With prefab houses, you simply order the kit, and then you can actually put the pieces together by yourself, provided that you have some construction experience. Metal & Pre-fab building kits from Worldwide Steel Buildings are perfect for garages, workshops, homes, barns, & more. Our custom metal building kits are great for commercial use. For more than 30 years, Worldwide Steel Buildings has been making custom metal buildings kits and pre-fab.