About Us


Founded by Sean Duffy and Erik Harley in 2009, H&D Mechanical is a mid-size mechanical contractor based in Upper Marlboro, Maryland. H&D has an established record of superior work in a variety of settings, including medical, scientific and commercial projects.

View H&D Mechanical notable projects here.

For information about Harley & Duffy, our residential plumbing, heating and air conditioning services branch, please visit: