Mark Lumley has been working in construction since the age of twelve. He spent years developing his skills in the field before founding Mark Lumley Builder — because he wanted to build homes the way he believed they should be built, with complete accountability to the client and no compromise on the standard of the work.
Today, Mark Lumley Builder builds custom homes, leads major renovations, and provides year-round estate management for homeowners across the Hamptons and the East End of Long Island. The company has grown. The standard has not.

We started this company with one guiding principle: do right by the client. Know what you are building before you build it. Use the right materials, the right methods, the right people. And when a project asks something of you that you have not encountered before, learn it — properly, thoroughly, without guessing.

Mark Lumley has been building since before most people consider it a career. He got his start at twelve years old, learning the fundamentals of the trade hands-on — what materials do, how structures behave, what separates work that holds from work that doesn’t. That early experience turned an inherited familiarity into a genuine calling.
He spent years developing his skills in the field before founding Mark Lumley Builder, a company he has led for more than two decades. Today, Mark remains deeply involved in every project — reviewing construction methods, supporting the field team through complex challenges, and ensuring the quality and precision that define the company’s work are present at every phase of the build. He is not a builder who manages from a distance.
When a project calls for something unfamiliar, his instinct is not to improvise — it is to learn. He researches thoroughly, consults the right specialists, and fully understands what the work requires before committing to it. The knowledge built in that process benefits every client that follows.
Outside of work, Mark stays active and spends time with his family. He is, as he puts it, always drawn to projects that involve creating or improving.

Justin Karagozi came to construction through the trades. He became a licensed electrician, ran his own electrical business for four years, then transitioned into construction management — bringing a tradesman’s understanding of how buildings go together from the inside out. He has been with Mark Lumley Builder for more than fourteen years.
As Estate Management Field Manager, Justin manages post-construction punch lists and coordinates the ongoing care of properties across the East End. He holds himself personally responsible for every job he is on — not just the tasks he performs directly, but everything that happens on his watch. Outside of work, he is devoted to his kids, deeply involved in Boy Scouts, and has a serious appreciation for plants and yard work.

Tom Joy came to high-end residential construction by an unconventional route. He began in the trades — carpentry, plumbing, site work — then moved into retail operations management, turning around underperforming stores under pressure. That combination of field experience and operational leadership is not common in construction, and it shows in how Tom approaches a project.

He has been with Mark Lumley Builder for eleven years, involved at every phase from bidding through closeout. More recently, his focus has shifted toward leading the company’s estate management division — extending the firm’s relationship with Hamptons homeowners well beyond the completion of their homes. Outside of work, family comes first: his wife and two sons, baseball, and a serious approach to landscaping.