Plumbing a Bathroom Into a Garage, Porch or Sunroom Conversion in Louisville

Why the Slab Changes Everything

In a room over a basement, new drains hang from the basement ceiling and are easy to reach. On a slab, every drain line for a toilet, shower or sink has to be buried in the ground beneath the floor. That means sawing and removing concrete, trenching to the nearest point where the new drain can connect, and patching the floor once the piping has been tested and inspected.

The location of that connection point drives the design. It might be the house's building drain under the basement floor next door, a cast iron line in a crawlspace, or the sewer lateral outside. We find it, measure how deep it is and confirm there is enough fall from the new fixtures to reach it.

Step by Step: New Drains Under a Slab

Here is how a typical slab job goes from marked floor to finished patch:

Garage floors are often sloped toward the door for drainage. If the converted room will get a raised subfloor to level it, we set drain heights to suit the new finished floor, not the old concrete.

• Mark fixture locations on the floor using the actual fixture dimensions
• Saw-cut and break out a trench from each fixture to the connection point
• Excavate to the depth needed for proper slope
• Lay new PVC drain lines on a firm, even bed, with cleanouts where required
• Set toilet flange, shower drain and sink stubs at finished-floor heights
• Test the underground lines and have them inspected
• Backfill, compact and patch the concrete

Getting Water to the New Room

Supply lines are often easier than drains. They can come up from a nearby basement, run through an interior wall or drop down from the attic. What they should not do is run through an exterior wall or an uninsulated attic in a former garage or porch, where Ohio winters can freeze them.

Flexible PEX tubing is a good fit for conversion work because it can be pulled through finished spaces with fewer joints. Where supply lines must pass under the slab, they go in a sleeve so they can be replaced later without breaking concrete again.

Venting and Coordination With Other Trades

Each new fixture needs a vent, which usually rises through a new interior wall and ties into the house vent system in the attic or exits the roof on its own. Because garages and porches were never meant to be living space, the conversion also involves insulation, framing, electrical and heating. We coordinate our work so trenches are closed and rough-in is inspected before the framers and drywallers need the space.

If the room only needs a fixture swapped rather than new lines, our plumbing installation services page covers that work.

Getting Started

We start with a free estimate at your home, where we locate the connection point and walk through fixture placement. Once you approve the plan, we schedule the slab work and rough-in, then return after the room is finished to set fixtures and make final connections. Read more about our process on the new plumbing installation page.