There’s nothing glamorous about waterproofing. It doesn’t dazzle in the portfolio and it likely doesn’t enter into most customers’ minds.
That’s why it’s an easy step to skip, as Alan Smith
sees during competitive bidding. He recently lost a high-end job in
Malibu, and he suspects the waterproofing cost was a culprit. His
company needed $3,500 for that part of the project, but the builder
who eventually got the contract didn’t mention waterproofing in the bid.
Unfortunately, Smith suspects, the customer will pay.
“It’s not if it’s going to be a problem —
it’s when,” says the owner of Alan Smith Pool
Plastering in City of Orange, Calif.
The omission or half-hearted execution of waterproofing becomes
visible soon enough in the form of efflorescence or delamination.
Vanishing edges are showing the most problems, with tiles and stone falling off.
And it’s not just a matter of brushing on a sealant.
“There are so many things you can do wrong during that
process,” says Gene Brown, president of Valley Pool & Spa
in Kelowna, British Columbia, Canada. “It’s a bit of an
art form all in itself.”
Here professionals discuss this process and its many considerations.
Though waterproofing is needed in different kinds of situations,
vanishing edges have been causing the most problems of late.
Of course, any surface that will be veneered with tile or stone
should be waterproofed, but some professionals have struggled with
vanishing edges resulting in efflorescence and fallen tile or stone
on the back side of the wall.
If a vanishing edge isn’t properly sealed, the falling water
can cause efflorescence to form. Perhaps less known is the fact
that water from the main pool can seep through the weir wall and
form efflorescence behind the tiles or stone on the back of the
wall. As the calcium builds up, it eventually can cause the
finishing material to pop off.
And it’s not just water. “It’s also vapor,”
says Greg Andrews, owner of Andrews Tile in Agoura Hills, Calif.
“If you get water or moisture entering from the pool side and
then the other side ... can heat up to 120 or 150 degrees, it can
actually pull vapor through.”
Because of this, vanishing-edge walls should be waterproofed on
both sides. Applying a system to the main-pool side keeps water
from seeping through. This is called the positive side because
it’s the source of hydrostatic pressure on the wall. Sealing
the back of the wall, or the negative side, forms a barrier in case
water does seep through, and also helps protect against the water
falling over the weir.
Many professionals will waterproof the entire wall inside the pool
— not just the section with spilling water. They often
continue adding the agent down the back of the wall, into the catch
basin and even over the lip of the catch basin. Different compounds
may be needed to address positive pressure and negative pressure.
Spa dams should be treated similarly. Many professionals will
waterproof the entire spa interior, as well as the face of the raised wall.
Because the weirs and backsides of vanishing-edge walls are always
veneered in tile or stone (since plaster and pebble surfaces need
constant immersion), Dave Peterson, president of San Diego-based
Watershape Consulting suggests following the instructions provided
by the Tile Council of North America to waterproof the weir and back wall.
Regardless of the situation, it’s crucial to use the right
system and apply it correctly. Contractors should begin by making
sure that the waterproofing agents they’re choosing are
appropriate for the project at hand.
Read manufacturer’s specifications to establish three things
— whether it’s appropriate for water vessels, whether
it protects against positive pressure, negative pressure or both,
and whether it can be mixed with other systems that may be needed.
Some companies will only warranty their products when combined with
others in their line. Additionally, makers of topical membranes may
not allow these products to be utilized in combination with
Don’t assume that because a system has been proven in other
types of construction, such as bridges or vaults, that it’s
appropriate for pools and spas.
“We have a different protocol for placing [concrete] than
other industries,” says Ken Milbery, divisional product
specialist for PoolCorp’s Pacific Division. “We apply
ours with force and we very seldom see the situation where
we’re basically adhering to a [formed and poured] shell.
Shotcrete and gunite ... it’s a more porous placement than a
compacted, integrated mix design from a ready-mix plant.”
“Some waterproofing materials are made to go under maybe an
elastomeric coating, not under something cementitious going over
the top of them,” Smith says. “You have waterproofing
materials that are designed to go under deck coatings on balconies,
and they don’t have pool water with acid and chlorine sitting
on them constantly.”
Often, contractors find themselves using at least two types of
waterproofing agents — one for around the fittings and
another for the flat surfaces. The material used around the
fittings must be thicker to fill the gaps, while the waterproofing
agent on the rest of the pool should be applied in a thin layer.
When applying the waterproofing system, start by inspecting the
concrete to make sure it’s in good condition.
If there are divots and holes, it may be necessary to add a float.
Some waterproofing products can’t fill holes in concrete, so
these materials need to be applied on the smoothest possible surface.
“Especially like with the shotcrete we use, the
aggregate’s fairly large so you tend to see a lot of
imperfections in the surface,” Peterson says.
Professionals also should look for hollow spots. This is
particularly important on vanishing-edge walls and others that are
self-supporting, because of how they’re constructed.
“Most times ... when they shoot the pool, they’re
generally shooting up against the earth,” Andrews says.
“But with infinity-edge walls, they’re shooting up
against a form, and there can be some vibration of the form and/or
the steel that’s in the wall.
When that happens, it can create voids, and if water gets to those
voids, then that can spell disaster.”
He not only performs a visual inspection, but taps around the wall
to check for hollow sounds. If he comes across one, he will chip
the concrete to expose the void and then fill it.
Contractors also should always ensure that the membrane will bond
properly with the next layer being applied, whether another coat of
waterproofing, a thinset or plaster-like material.
“The issue you’ll run into is the membrane will stick
to the concrete no problem. But the problem is getting the pebble
or one of those finishes sticking to the membrane,” Brown
says. “Once they’re dry, they’re now really
waterproof, so the next layer has a hard time biting into that
— because they’re doing what they’re supposed to do.”
Manufacturers may recommend a particular bond coat to be placed
over their product. But if the waterproofing agent is cementitious,
applicators should somehow rough up the surface, whether it be by
running a notched trowel over the top to create a grooved pattern
or texturing it with a brush or roller.
“If you do not follow those instructions you can end up with
a surface that’s way too smooth and you’re not able to
bond to,” says Jay Eaton, general manager of Phoenix-based
Cal Plastering Co. “Then it’s like trying to put pebble
on glass. It won’t bond.”
Once you’ve determined the product is appropriate, it’s
important to follow the instructions to the letter. There may be
more steps required than you realize.
“There’s actually a lot to a membrane, and if you
really go through how it’s supposed to be done, there are a
lot of steps that most people just run over,” Brown says.
For instance, some products must be applied within certain
temperature ranges. Some are more sensitive than others. Because of
this, Brown often tents his projects as he’s waterproofing
them. “Part of this is for sun and to keep the adhesives from
flashing to the membranes and getting some weird drying
aspects,” he says. “It doesn’t matter if it rains
or there’s sun, because all of it’s bad. You just want
to keep a nice, constant temperature. If you seal it up and sort of
treat it hermetically where it’s a controlled environment,
then you’ll generally have success.”
In one recent Phoenix-area project, plasterer Eaton not only had to
tent the pool, but he and his crews also had to use coolers.
“We couldn’t use the [waterproofing] product because it
was just too hot,” he says. “I believe we were keeping
the structures at 78 to 82 degrees.”
While not always necessary, tenting also helps with another
important aspect of waterproofing — maintaining a clean environment.
Manufacturer instructions may even specify a rate at which the pool
should be filled, and how much time should pass before it is heated
for the first time.
Other waterproofing systems don’t work well when placed
around hard corners, which may cause the layer to crack. If this is
the case, instructions will explain how to round out the corners to
make the surface more effective for the compound.
If the membrane is being applied to a pool built over a house or
other structure, it’s best if plasterers don’t puncture
it by walking with spikes. To avoid this, Smith’s crews will
place a thin layer of cement or other substance on it so crews can
walk on the floor without puncturing the membrane.