Long Island and New England's Choice For Building Supplies For Over 70 Years. Builders, contractors, architects and homeowner ... s throughout Long Island and New England count on us for a broad range of building supply products and specialty services. From lumber, tools, hardware and paint to fine cabinetry, flooring, kitchen design, windows, and custom molding, we have the premium building materials and service selection you need to make every project a smooth success. Riverhead Building Supply is conveniently located throughout Nassau and Suffolk Counties in New York, and in the communities of North Kingstown and Middletown, Rhode Island. The company employs over 600 full-time and part-time employees among 14 retail locations, 6 showrooms, distribution services, manufacturing and custom millwork, and our corporate office location. We rely on a knowledgeable team of distribution and delivery personnel, craftsmen, store management, buyers, IT specialists, accounting and finance specialists, and estimating, sales and marketing professionals to keep all areas of the company running smoothly, and to ensure that our customers find the right products in our stores, at competitive prices. read more