Basement Bathroom and Laundry Addition in South King County

Single-bathroom homes put a real strain on daily life. Morning routines back up, guests are uncomfortable, and resale value takes a hit. Adding a basement bathroom is one of the most practical upgrades you can make - and that's exactly what we tackled on this South King County job.

Here's what the scope looked like: a fully permitted 3/4 bathroom with a shower, toilet, and sink, plus laundry hookups and a backwater valve to protect against sewer backups. To get there, we had to cut and break through the concrete slab floor to access the existing sewer lines and rough in all the new drain lines below grade. That's the part most homeowners don't think about - before any framing or fixtures go in, there's serious concrete and excavation work happening first.

Once the underground plumbing was set and the concrete patched, we framed up the bathroom walls and ran all the supply and drain lines through the framing. Hot, cold, and drain - everything stubbed out exactly where the fixtures needed to land. The laundry hookups went in the same area, making this one compact but fully functional space.

We also installed a backwater valve on the sewer line. This is something we always recommend for basement bathrooms. If the municipal sewer ever backs up - which does happen - that valve keeps sewage from coming back up through your basement drains. It's a small addition with a big payoff in peace of mind.

Pulling the permit on a job like this isn't just a formality. It means the work gets inspected, it's done to code, and it shows up correctly when you sell the house. If you've been living with just one bathroom or you've got unfinished basement space sitting idle, this is the kind of remodel that pays for itself.