A great post at prefabcosm for anybody in the US looking for specialists in modular building, whether that be for building your own home or a garden office/shed. Click here to go to the National Association of Home Builders' site which has organised the directory. This is how they describe it:
"Use this directory to locate modular manufacturers across the country that can deliver your new home! Most modular manufacturers have local or regional representation or a network of builders to put the finishing touches on your dream home."