About glass block
Molten glass was first injected
into glass block molds in 1937,
and glass block has been a staple of
contemporary architecture ever since.
Although other building fads come and go, glass block continues
to capture the imagination of designers, builders and
The smooth, impervious nature of glass
block makes it a fantastic substitute for
ceramic tile in a shower. With its patterns
and sparkle, the block itself is beautiful,
and it allows natural light to flood
through the walls into the shower.
Before you begin, stock your tool belt with
plenty of patience. Glass block
work is a skill that's very aggravating
to master. Blocks can't be
cut or trimmed, and their nonabsorbent
nature makes mortar
work especially tough. But if you
don't try to rush the job, your
work can look as good as any
A note on installing new
bathrooms: Before you run out
to buy a truckload of glass block,
be aware that converting a bedroom
into a bathroom requires
extensive work beyond the
plumbing. You may have to
reroute heating ducts, eliminate
existing windows, shift electrical
outlets and remove possibly
load-bearing interior walls. Run
the design by a building inspector
to get the necessary permits
and inspection schedule. One
other warning: If you plan on
taking long showers using two
shower heads, you might need
another 40-gal. water heater.
Editor's Note: For information on building the shower base and tiled wall shown in this article, see How to Build a Shower Pan.
Bathroom and bedroom before remodeling.
Before and After
A shower the size of this one won't fit in an
average-sized bathroom. Ours was made
possible by stealing the bedroom of a college-bound lad. His loss became his parents'
Glass block basics
This shower uses the most common,
widely available style of
glass block: the 8 x 8-in. “Decora”
pattern manufactured by
Pittsburgh Corning. We used
two types of specialty blocks for
the ends and the outside corners
of walls. End blocks have
rounded profiles on one edge;
end curve blocks have two
rounded edges and one rounded
corner (see Photo10). The blocks
have a nominal dimension of
8 x 8-in., which means that the
actual block is a bit
smaller. When 1/4 in. of
mortar is added, the
dimension of the block
plus mortar is 8 full inches.
Because blocks can't be
cut, you need to carefully
consider the length and
width of new and existing
walls well before pursuing
the project. Planning the
height and width of your
shower is absolutely critical,
especially if you're
going to be filling the space
between two walls or
between the floor and ceiling.
Because our shower
didn't reach the ceiling
and wasn't contained by
walls, our design was very
The job will go much smoother if you
buy a few of the tools used by the pros.
You'll want a brick trowel, a
mortar joint striking tool and a
small plastic mortar-mixing box with a
hoe. Good 2-ft. and 4-ft. levels are
essential to keep the blocks level and
plumb as you set them.
Lay out the glass block grid on the floor
To get a feel for the size and design of
the finished walls, we used a chalk line
to snap a full-scale grid of the 8-in.
block wall on the floor. It helped us
establish the stair-step pattern on the
curved wall and made it easy to count
each type of block needed for the project.
Counting the rows also told us
the quantity of panel anchors, spacers
and panel reinforcing we needed.
When you're planning the overall size
of the glass block walls, keep in mind
that the 8-in. dimension only allows
for one mortar joint per block. You
have to add another 1/4 in. for each
wall and ceiling joint. Make 8-in.
marks on the wall to establish the
height for each row (Photo 2). Plastic
spacers don't work on curved walls
(for alternatives, see “Glass Block
Hardware,” below). Special, but spendy,
curved glass blocks or
4 x 8-in. blocks are
available for tighter
curves, if you need them.
Build and tile the shower base
Find details for the construction of
this shower base in How to Build a Shower Pan.
We decided to tile the entire
shower base and walls before starting
on the glass block. That way, tile on
the walls that would meet the glass
block could be rough-cut to width,
because we ended the tile behind the
block (Photo 9). The block butts into
the tile and eventually the seam will be
sealed with a bead of clear silicone
caulk. On the floor, in the dry-off area,
we could also rough-cut tile that
would run partially under the glass
block wall. The advantage of this method is that tiling goes quicker and
easier if there aren't any walls to walk
around. However, doing the tile first
means having to protect it while you
do the block work. Use masking tape
to hold cardboard together and to
cover any nearby tile.
Glass Block Hardware
All the hardware you need to
build glass block walls will be
available wherever you buy
your glass block.
Panel Reinforcing: It looks
like a galvanized wire ladder,
and you'll need to lay it on top
of every other row of block
before applying the mortar.
Panel reinforcing ties the rows
of block together and strengthens
the whole wall.
Spacers: Building straight
walls is much easier because
you can use plastic spacers
made specifically for glass
block. Use the T-shaped spacers
floors and walls.
Cut one leg
spacers to make
and floors. Use
work for curved
walls. Use carpenter's pencils
or 1/4-in. plywood spacers as
temporary guides. Remove
them before striking joints,
then tuck mortar into the voids.
Panel Anchors: These metal
straps tie the block walls to
existing walls and are installed
every second row.
Back to Top
Mix a half-hour's worth of mortar at a time
When you're learning the ropes, mix
just a couple of coffee cans' worth of
mortar at a time. Add enough water to
the mortar so that it will slowly slide
off the trowel when you hold it vertically.
The pros will put an accelerator
into the mix to speed up the setting
time, but rookies should play it safe
and use the extra time to set, level,
plumb and adjust the blocks.
Wear rubber gloves when working with mortar, and safety glasses to
avoid accidental splashes in the eye.
Constantly work the mortar mix with
the trowel to keep it smooth and consistent.
Don't do more than two rows
of block at a time, or the weight of the
top rows will cause mortar to squish
out of lower joints. (After an hour or
so, the mortar will harden enough to
permit another couple of rows.) Let
the mortar sit about a half-hour (or
until the mortar starts to stiffen)
before striking the joints with the
striking tool. Then go over the whole
surface with a soft brush to remove
loose chunks. Wait another half-hour
before smoothing mortar joints with a
sponge. After the mortar dries to a
haze on the blocks, polish the block
with a clean, dry towel. You don't
have to complete all these steps before
starting to set other rows. While you're laying more block, pause occasionally
and go back to perform these
tasks on previous blocks. Above all
else, continually check all blocks to be
sure they're aligned, plumb and level.
When your shower wall is done,
wait a week, then apply a high-quality
silicone grout sealer to the shower
side of the wall to prevent mildew and
stains from ruining the appearance of
the mortar. You can use the shower in
the meantime—a few showers that
week won't harm the grout.