The original master bath in our client's house had only 36 square feet of floor area, barely enough room to turn around in. Though we sketched out some preliminary designs that would provide more space, we had to shelve them when we discovered our proposed addition would straddle a 10-foot-wide utility easement that included a major sewer line for a nearby housing development. Staying within the existing footprint and expanding into an adjacent guest bedroom wasn't an option, so instead we overlaid the easement onto the site plan and designed within the space left inside the county's required 5-foot setback. The result was a 115-square-foot six-cornered addition, with each corner no closer than 5 feet to the sewer line. The "stepped" design is a little unusual, but our clients love the way it dresses up the rather nondescript gable end.
To give the interior a contemporary European look, our staff architect designed the room so that nothing touches the floor. The maple cabinets hang from the walls, and even the toilet sits up off the floor, thanks to a hidden wall-mount system. The radiant tile floor is also a key part of the design; it's laid over Wedi backer panels, which simplified installation of the radiant tubing and construction of the curbless shower.
Foundation and Framing
The addition sits on a conventional poured concrete frost wall. Because the small footing required only 2.5 yards of concrete - a short load in our area - it was more cost-effective for us to mix it ourselves, even though it took 38 80-pound bags. After forming the 48-inch-high stem walls, we called in a pump truck to fill them. We insulated the walls from the inside with 2 inches of EPS foam, covered the ground with a 6-mil poly vapor retarder that we taped to the insulation, then backfilled to grade with dirt.
Framing. Whenever we're working on a job that will have a lot of wall tile, we frame with engineered studs. Though more expensive than standard framing lumber - around here, a standard 2x6 stud costs about 40 cents per foot, while 2x6 TimberStrand LSL (woodbywy.com) studs cost about $1.50 per foot - engineered framing is straight and defect-free, which makes it much easier to get a good-looking tile job. The $420 or so it added to the cost of materials was somewhat balanced by the savings in both waste and time that we'd otherwise have spent correcting the framing.
Even though our zone 5B climate isn't particularly severe, I still don't like to put plumbing in exterior walls and run the risk of freezing pipes. To provide room for additional cellulose insulation, we framed double walls in the shower and toilet areas. This allowed us to easily meet energy code requirements in our area - which specify at least R-21 walls - and to move the toilet's 4-inch-diameter waste pipe away from the foundation wall.
