Framing Shower Stalls
Determining where a prefabricated shower stall goes depends on where the shower pan sets. Therefore, you'll probably need to purchase the shower first.
Then measure the base dimensions, transpose its outline onto the subfloor and mark the drain location at the same time.
Assuming the stall's back will be against a wall, cut 2 x 4 bottom plates, position them on the side base marks and anchor them in place with construction adhesive (optional) and screws/nails.
Set vertical end studs on the bottom plates. Butt the end studs of the stall walls to the main wall. Add nailers to the main wall if needed. Fasten the end studs to both the main wall and their bottom plates.
TIP: Use greenboard when drywalling around the shower stall. Adding felt strips to framing studs can provide a snug fit for the stall.
Framing A Whirlpool Tub Deck
Installing a whirlpool tub starts with framing its deck with short stud walls. This "blocking" is nailed to the main wall framing, subfloor and floor joists.
Most codes will also require a built-in access panel for the tub's motor which is handy in case it fails or needs servicing.
Frame the basic "box" walls by cutting and nailing together the bottom plates, studs and top plates. Space the studs on 16" centers -- doubling the corners and access opening.
Fasten plywood decking to the top and sides of the box. Then cut a hole for the tub to set in. Apply a mortar bed over builder's felt where the tub will set.
Position spacer blocks around the deck so the tub's lip will be at the deck's finished height. Set the tub and embed it in the mortar.
Vapor Barrier & Insulation
Building codes require exterior walls to be insulated and protected with a vapor barrier. That's usually done after the electrical rough-in, but we'll mention it now to finish up framing.
Fiber glass insulation is often used because it's easy to work with. Likewise, a 4mil or 6mil clear plastic vapor barrier is commonly used.
Staple the vapor barrier to wall and ceiling framing. Also, tape any holes or rips made in the barrier.
Insulation provides comfort and energy savings. That's fairly well-documented. But it's the vapor barrier that protects insulation and framing from moisture; which is always present in bathrooms.
Exhaust fans and windows help to get rid of moisture, but it can still penetrate cooler exterior (or interior) walls, condense into water, cause insulation to lose its effectiveness and damage wood.