Radon Rough-In for New Construction

The cheapest time to deal with radon is while the slab is still open sky and the walls are still studs. A passive rough-in is a pipe run from beneath the slab up through the interior of the house and out above the roofline, installed during construction, capped and labeled, with no fan on it. If the finished house tests low, the pipe simply sits there. If it tests high, a contractor adds a fan and the passive system becomes an active one without opening a single finished wall.

Compare that to retrofitting. In a finished home, the same work means coring the slab, finding a route that does not run through living space, and often putting pipe on the exterior. All of it is routine and none of it is a problem, but it is more labor and more visible than a pipe stubbed in before drywall. If you are building along the Wasatch Front, this is a small line item to raise with your builder early rather than a decision to revisit later.

What a passive rough-in includes

• Gas-permeable layer. A layer of clean aggregate beneath the slab that lets soil gas move freely toward the pipe, rather than sitting in pockets the system cannot reach later.
• Sheeting under the slab. Plastic sheeting laid over the aggregate before the pour, lapped and sealed, which limits how easily soil gas moves upward through the concrete floor above it.
• The vertical pipe run. Pipe stubbed into the aggregate layer and run up through interior framing to above the roofline, sealed at every joint, so a fan can be added later without new routing.
• Capping and labeling. The pipe is capped and labeled as a radon system, so future trades, inspectors and owners know what it is instead of guessing at an unmarked stub.
• Power for a future fan. An electrical junction placed near where a fan would eventually mount. Adding it during the build is trivial; adding it afterward means running a circuit through finished space.
• Crawl space provisions. Where a crawl space is part of the design, a sealed membrane and a draw point are planned in from the beginning rather than added under a finished house.

How the rough-in fits the build schedule

Raise it before the pour

The aggregate layer, the sheeting and the pipe stub all have to be in place before concrete. Once the slab is poured, this specific opportunity is finished for the life of the house.

Route it before drywall

The vertical run goes up through interior framing while walls are open, terminating above the roofline. Choosing the route now avoids exterior pipe and awkward chases in the finished home.

Cap, label, document

The pipe is sealed and marked, and the location is recorded. Ask for it on the plans and in the closing documents so the next owner is not discovering an unexplained pipe.

Test after move-in

A rough-in is not a result. Once the house is occupied and operating normally, test it. If the number warrants it, a fan is added and the passive system becomes active.

What it costs

Rough-in pricing follows the same physical drivers as other radon work, at an easier moment. House footprint and foundation type set the scope, since a larger slab, or a design with both a slab and a crawl space, means more aggregate, more sheeting and possibly more than one draw point. Where the pipe can be routed matters: a straight interior chase to the roofline is simple, while a plan with no clean vertical path costs more. Fan sizing only enters if the system is later activated. A sump or drain tile designed in as the draw path simplifies things further. Retrofitting the same house later is the expensive comparison.

Questions people ask