While traditional shower designs usually include a floor with a
raised front edge to contain the spread of water and splatter, this
raised edge is not an absolute requirement. Shower basins can
be fitted into a floor in such a way that the existing level floor
transitions smoothly into a shallow, sloped basin.
The basin is curved enough to ensure efficient collection of water
toward the drain, but shallow enough so that stable footing is not
compromised. The smooth transition from level floor to sloped
basin, unencumbered by any type of a water barrier, produces a
sleek and clean appearance. It also eliminates a “trip hazard”.
Showers with smooth, “flush” transitions are also referred to as
“barrier free” showers, because they pose no barrier to a person
getting in or out of the shower alcove. They are also referred to
as “roll-in showers”, because they are naturally accessible to
bathers who use wheeled devises, such as walkers or wheelchairs.
While the terms “barrier free” and “roll-in” are descriptive, the
smooth transition design is quite appealing in its simple
elegance. The lack at the shower entry of a visible, high profile
water barrier is a subtle statement that can play together well with
accompanying finishes and the overall layout of the bathing area.
Even “typical” and “regular” bathrooms gain flair and uniqueness,
in an understated way, by eliminating one feature, the water
barrier, that is customary and expected in a bathroom.
Installation of Smooth Transition Shower
The walls of a barrier-free shower are created the same way as
for regular showers. It is the floor that requires more attention.
If the transition from a level floor to a sloped basin is to be
“smooth”, the line where the two portions of the floor meet must
end out finishing at the same height. The bottom of the basin,
where the water drains, must somehow finish at a lower elevation
than anywhere else on the entire bathroom floor.
This cannot be accomplished by raising the elevation of the level
floor, because then there would be a major problem where the
bathroom floor meets the floor in the rest of the house. As soon
as someone opens the bathroom door, they would have to step
up a couple of inches onto the higher floor. Also, everything else
would be offset: There would be plumbing issues where the toilet
and vanity connect; height issues with recessed medicine cabinets
and windows; clearance issues with linen closet doors. In general,
raising the elevation of the level floor is not an option.
The solution is to lower the floor under the shower floor basin.
This can be done by eliminating the floor and subfloor and
exposing the floor joists. The joists can then be notched
lengthwise so that the cut top of the joists are lower than their
uncut neighbors. This provides a lower starting point for
rebuilding the shower basin floor, and results in a lower finished
surface when the whole thing is complete.
The amount that the joists are cut down is calculated by
subtracting the depth of the shower basin from the height of the
finished floor. Between 1 ½ “ and 2” is an adequate depth for a
shower basin, but less than this needs to be removed from the
joists. By blocking and inserting the new subfloor between the
joists, usually only a small fraction of an inch needs to be removed
from the top of each joist under the shower area.
Joists that have been cut back in this manner can be reinforced
by sandwiching them with 1/8” thick steel through-bolted with ¼”
bolts. The steel should run the length of the joist, ending on top
of supporting structures on either end.
Once the subfloor has been positioned height-wise in relation to
the anticipated height of the level floor, the shower basin can be
installed. If the shower basin and the level floor are made of
dissimilar materials, the joint between them will be made watertight
with 100% silicone caulk.
If the shower basin and the level floor are finished with contiguous
and newly installed ceramic (or porcelain or stone) tiles, water
tightness will be assured by a membrane underlayment. The
membrane underlayment is installed as a single sheet under the
ceramic tiles. It flows, uninterrupted, across the level floor and
into the basin, sealing the transition from water leakage.