H.T. Harrison & Sons is a full-service company that offers a variety of roofing products and accessories to residential and commercial customers. The products offered by the company include slate and metal roofs, shingles, modified systems, plywood replacement and built-up roofing systems. The company also specializes in fire retardant-treated plywood replacement. H.T. Harrison & Sons has been operational for more than 100 years and is located in Rockville, Md.