Unfinished basement turned into a family room in Durham

The scope

A 1978 split level in Durham with a full walkout basement that had been storage for nearly fifty years. The owners wanted a family room, a home office and a bathroom rough-in for later, and had been told by two other contractors that the space was fine to finish as it was.

The challenge

It was not fine. The floor was dry to the touch and the relative humidity down there sat well above sixty percent all summer, which is a mould problem waiting for a stud wall to grow on.

Finishing a basement that has not been dried out first is the most expensive mistake in residential remodelling, because the damage happens inside a wall you have just paid to close. So the first two weeks of this job produced nothing the owners could see.

The second issue was air. The existing system had no return anywhere below the main floor and one undersized supply, so a finished basement would have been a cold, stale room that the owners would have stopped using by the second winter.

What we did

Water first. We regraded the two problem corners outside, extended the downspout discharge well clear of the wall, sealed two cold joints, and ran a dehumidifier on a hygrometer for ten days to confirm the space held below fifty percent before framing.

Then insulation, and this is where basements in this climate differ from basements anywhere north of here. Rigid foam against the concrete, taped, with the framing held off the wall and no vapour barrier on the warm side, so the assembly can dry inward. A polythene sheet on the inside face is how you build a mould sandwich in Piedmont summer humidity.

The ductwork crew added a properly sized supply run and, more importantly, a return, so the basement is on the same conditioned loop as the rest of the house. The lighting is recessed on two zones with the office switched separately.

The bathroom rough-in went in under the slab while it was open, capped and pressure tested, so the owners can add the bathroom in a few years without cutting concrete twice. Details of how we approach these are on the basement finishing page.

The outcome

Eight weeks, two of them before a single stud went up. The room holds temperature within a degree or two of the rest of the house and the humidity has stayed in range through a full Triangle summer, which is the number the owners actually care about.

The dust during the concrete cutting phase was worse than we had prepared them for, and that complaint reached us in writing. Negative air containment is now in the standard scope on any basement job that starts with cutting concrete. Finished 27 February 2026.