Building a traditional shower base
These days, if you want
to put in a shower, you
can just go to a home
center and pick up a
fiberglass unit. Before
that was possible, pros
had to build a shower pan
base by mixing and
applying mortar, troweling
it flat, and laying
units make the job quick
and easy, they lack the
elegance of a handcrafted
mortar and tile
floor. So if you'd like to
install a tile shower and
are willing to build your
own shower pan, you'll be able
to tile it to match the
walls. And with a mortar
and tile floor, your shower can be any shape. (For instance, see How to Install a Glass Block Shower.) In fact, no matter what its shape, if the
shower you have in mind doesn't conform to the rigid
size requirements of a manufactured base, a mortar floor
may be your only alternative.
You'll find that the cost of the materials used in a
hand-crafted base is roughly the same as the cost of a
comparably sized fiberglass pan. The downside is that
instead of just plugging a manufactured unit into the
opening, you'll have to do a lot more work. You'll need a
couple of days to form and tamp in two layers of mortar,
deal with some tricky vinyl membrane liner work and
then install the tile. This isn't a project for winging it or
taking shortcuts. A poorly installed base will leak, and
the only correct way to fix a poor installation is to rip out
not only the base but also the shower walls.
Don't let the complicated shower floor featured in this story scare you (the floor is designed to complement the story on How to Install a Glass Block Shower). The fundamental techniques are the same for even the simplest shower, so pay attention—even if you're installing a shower the size of a phone booth.
The professional who helped us could have completed
our floor in less than a day with an assistant if we
hadn't slowed him down by taking these photos. If you
have experience with cement and some basic trowel
skills, you should be able to do almost any size shower
floor in less than two days, excluding tile work.
This shower weighs upward of 1,000 lbs., or about the same as a spa with a couple of people in it! If you live in an older home with 2x6 or 2x8 floor joists, you may need to beef up the floor with some beams or extra floor joists. If you're unsure, consult a building inspector. And if you have a house that was built in the '70s, it could have a 5/8-in. particleboard underlayment that will need to be removed before starting.
Buy your materials at a tile supply house
You can run all over town trying to round up the special
tools and materials you'll need. Save aggravation and
get it all at a store that specializes in ceramic tile. It'll not
only have everything on hand, but also help calculate
how much of everything you'll need. Bring in a scale
drawing of the shower to make the job easier.
Here are the basic materials:
- An 80-lb. bag of ceramic floor mix for every 4 to 5
sq. ft. of shower floor area. (Buy extra and return
- CPE membrane (the vinyl liner) 12 in. longer and
wider than your shower. The maximum width available
is 6 ft. If you need to go wider, you'll need to consult the
manufacturer's instructions for lapping and welding
- Enough galvanized expanded metal lath to cover the
floor, with an extra 12-in. width to handle any curbs.
- Some hot-dipped 1-1/4 in. roofing nails to fasten the
membrane and the cement board.
- A roll of fiberglass tape to tape the seams of the
cement board. Be sure to buy the heavy-duty type for use with thinset mortar, not the light, self-adhesive type used for taping drywall.
- Enough 2x4 material to form the curbs, and enough
smooth 12-in. hardboard siding ripped down to
3-1/2 in. for curved curbs.
(Editor's Note: Since this article was first published, new materials have become available for projects like this. See Pro Tile Tips for more information.)
Anatomy of a Mortar Shower Floor
The first layer, called a sloped fill, is simply a mortar
subfloor. It's sloped toward a special two-piece
clamping-type drain (available at any home center) that is made specifically for a mortar bed shower floor. The sloped fill slants from the
drain toward the perimeter of the shower with a
slope of 1/4 in. per foot. Since our shower had an
average width of 3 ft., we sloped up from the 1/4-in.
thickness of the drain to a 1-in. thickness around
the shower walls and curb to get the necessary
The second layer, called the pan, is a durable CPE
(chlorinated polyethylene) membrane. This vinyl
liner is turned up at the edges to create a waterproof membrane in the shape of a shallow pan.
Water that works its way through the grout and the
top layer of mortar will flow down the slope to be
drained through the weep holes of the drain. On top
of the pan is a layer of expanded galvanized metal
lath to reinforce the mortar. Over the lath a sloped
mortar bed is laid using the same 1/4-in.-to-the-foot
slope rule we used for the sloped fill.
Shower curbs help by containing water in areas
that aren't bordered by walls. If a drain becomes
blocked, perhaps by a washcloth over the surface, a
curb buys you time. It will dam the water within the
shower for a while before it lets it run over onto the
(For a larger version of this drawing, see Additional Information, below.)
Design and Layout
First, establish the shape and size of your
shower. Our shower had several requirements.
We wanted a shower that would comfortably
accommodate two people and have
two separately controlled shower heads. We
also wanted a curved glass block wall on two
sides and a drying area that was part of the
same shower. The specifications for curving
8-in. glass block required a radius of no less
than 65 in. After trying several arrangements
on the floor using properly spaced glass
blocks to help define the shape, we settled on
a 24-in. (three glass blocks) straight run
before beginning our curve. The size of the
dry-off area was arbitrary. We just stood
there and pretended to dry ourselves off and
decided it was right.
Keep these elements in mind when you're
sizing and positioning your shower:
The tile layout. It's easier to determine the
size of the shower if your wall tile is selected
ahead of time. Since we had 12-in. tile, we
made small alterations in the size until we
had wall lengths that made full tiles come out
just behind the inside edge of the glass block.
Shower doors. If your shower will have a
door, pick it out in advance to make sure the
shower opening will accommodate it. Don't
forget to allow for the thickness of the tile and
the cement board. When you're determining
the size of the shower door and the direction
it should swing, consider other bathroom
doors and fixtures.
Plumbing. It's obviously much easier to hook
up a new shower that is located near existing
plumbing. Copper water lines, sewer drain
lines and vents can be hooked up to pipes at a
neighboring bathroom. Our shower backed
up to a common wall that contained all the
plumbing we needed. If you're installing
your shower in a remote location, it can be
tough to get to the sewer drain and still keep
the shower drain within the required distance
from the drain water vent. You may need to rip out walls or the ceiling below
the shower to accomplish hook-ups if the
next level down is finished. Sometimes
plumbing a new bathroom is more work
than building the shower from scratch.
Now that the shower is laid out, it's
time to rip out the walls and rough in the
plumbing. Cut the drywall out of the
shower opening with a utility knife and
remove it. We made our cutting line fall
in the middle of the glass block. That way
the seam between the drywall and cement
board would be hidden behind the glass
block, and we could easily slip backing
boards behind the drywall to support the
splice and to tie in the glass block later.
After you plan your plumbing hook-ups,
cut a hole for the clamping-type drain in
the subfloor near the center of the shower
so that the bottom flange of the drain rests
on the subfloor. You may need to make
small notches in the floor to allow for the
plastic nubs that protrude from the sides
of the bottom flange. Rough in the copper
plumbing and drain water lines.
Form the outline of the shower floor
with 2x4s in the straight areas. Toe-screw
forms to the floor from the outside so you
can easily remove them later. Hardboard
siding ripped to 3-1/2 in. widths works
great for handling curved curbs. The
slope fill can be tricky to
install because its 1-in. height is 2-1/2 in.
below the top of the forms. For screeds,
use permanent 1-in. strips around the
walls and removable 1-in. strips to get the
correct slope against the curbed edges
(see Photos 4 and 5). After getting the
sloped fill tamped into place, we lifted
these blocks out and went back and filled
in the voids. Don't worry too much about
the finish on the slope fill; just make sure
it has the proper slope toward the drain. It
just serves as a sloped base for the vinyl
liner and as a base for the upper layers.
Install the cement board walls by
setting them over the liner and on top of the sloped fill. Use hot-dipped roofing
nails or the coated cement board screws
that are available at the same place you
buy your cement board. Tape the seams
with fiberglass mesh tape and cover them
with either thin-set mortar or mastic,
whichever the tile store recommends for
setting your tile. When setting the cement
board, face the smooth side out. This
makes it much easier to spread the tile
adhesive and get a flat surface for tiling
and for drawing tile layout lines.
Cut the lath with a pair of tin snips and
lay it on top of the membrane. Be very
careful cutting and fitting the lath. Avoid
walking on the lath. Its sharp edges can
puncture your waterproof membrane.
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How to get curbs the proper width
The width of the curbs on our shower
was determined by the width of the glass
block. We used 4-in. thick blocks, which
have a real width of 3-7/8 in. We wanted
the finished curb, including the tile, to be
slightly narrower than the block, so we
subtracted the two layers of 3/8-in. tile
(1/4-in. tile, 1/8-in. mastic) on each side
of the curb from 3-7/8 in. and wound up
with a curb 3-1/8 in. wide.
Since the top mortar bed is the tiling
surface, make it as even as possible. Use
the straightedge to locate high or low
areas. Pack in mortar to fill depressions,
and scrape off excess in the high spots.
Use a steel trowel to smooth the bed and
to tool sharp edges at all corners for a
cleaner tiling job.