Design and
Construction
It is worth understanding how a pool or spa
came into being; so this chapter is designed to give you a better
understanding and knowledge only and not make a pool or spa builder
of you. You will find a list of excellent resources to help you
taking into consideration, your ground plan, slope and geology, wind
and sun conditions, landscaping, home value, and a host of other
planning and building aspects.
As a pool owner or a technician or someone
buying a home with a pool, or one wanting to get a pool constructed,
you will want to recognize good (or bad) construction. This
knowledge will help you estimate the maintenance costs, future
potential repair expenses, or problems involved in upgrading the
pool or spa in question.
Constructing a new pool must be carefully
considered and planned. Consider the location of all underground
utilities: Electric/Phone, Natural gas; Septic; Wells; Home
foundation drain tiles/land tiles and the flood zone.
When all utilities and underground water
systems have been located, your swimming pool can be positioned to
the best possible location. Position is determined by land layout,
pool size, shape and available swimming pool area.
The architect or pool builder supplies plans
and an engineer provide the steel (rebar) schedule based on
calculations of soil stability, geology, etc. Then the local
building permit is issued when plans and steel schedules are
approved. The schedule includes the specifications of thickness,
tensile strength, how strong the final product needs to be.
Careful planning should include consideration
of backyard access, to heavy equipment. While excavation too these
underground utilities should be handled carefully.
Excavating must be well planned and executed.
Pre-planning always saves time. Firstly the outline of the pool is
marked with stakes and adding 2 feet to each side and end. Mark
these outlines with flour or chalk or lime. After the digging line
has been marked, the rough excavation starts. The excavator digs
according to the plan plus one foot to allow for the thickness of
material and plumbing. He digs straight down approximately 3 feet,
then slopes the remainder to the bottom. The actual slope and
contour of the pool is determined by the rebar sculpting. The
excavator also cuts out a 2 cubic foot area for each skimmer and for
each light to be installed. He also trenches from the poolside to
the equipment area for laying pipe. It should also be the
responsibility of the excavator to remove the dirt from the job
site, as well as tamp down, compact, and add a layer of gravel to
the finished hole. The gravel aids drainage if groundwater is
present from below or if leaks occur in the structure.
Usually the plumber lays in his plumbing first
then the steel rebar is laid. Skimmers are laid in where the
prevailing wind in that area will push debris toward them, if
needed. Plumbing must be at least 18 inches below ground and gas
lines 12 inches below (unless PVC gas line is used which must be 18
inches below as well).
The plumbing includes the main drain and
skimmers, pipes to the equipment area and back to the pool, return
outlets, automatic cleaner piping, waterfall lines, a water filler
line, or other design requirements. All plumbing is then sealed off
and tested under pressure to test for leaks. Some large pools or
commercial installations might have water sent back to the bottom of
the pool for even distribution of filtered water, chemicals, and
heat. Also refer to Plumbing System and Advance Plumbing Systems
Sections.
The rebar is laid in a crisscross pattern,
tied together with heavy wire to create a large, single, mesh bowl
and sculpted to the final contour and design of the pool. Generally,
rebar is centered 12 inches apart on pool walls and 6 inches apart
on the bottom and stress points. The steel man must be sure to
closely cut the ends of these ties for long, loose tails that stick
up will rust and later show through the gunite and plaster layers.
Heavier steel is often used for the top 12
inches and over the edge, called the bond beam. The bond beam
supports the coping and sometimes the edge of the deck, so it must
be extra strong. Sometimes the bond beam extends up several feet
above the waterline for waterfalls or tile areas. If the job is a
vinyl-lined pool, this steel process will instead be the layout of
the support structure.
An important part of pool building is the
electric work which should be performed by the licensed electrician.
The electrician grounds or bonds the steel (and any other metal
within 5 feet of the waters edge). He also adds light fixtures,
which must usually be at least 24 inches below the water surface.
Pool bonding or grounding is necessary to protect the pool and the
homeowner, thus bonding is required on all swimming pools and should
be inspected by the local building and zoning. Most electrical lines
require a GFCI and all the electric codes are strictly enforced.
Electrical work must be perfect and in
accordance to local, state and national codes. For further details
refer to Basic Electrical Section.
The exact gunite or shotcrete mix is specified
by the engineer based on strength and weight-bearing needs (as you
have seen, water weighs a lot!). Often the mix will be five parts
sand or gravel to one part cement.
The mixture is shot under pressure with a hose
and nozzle from the mixing truck in and around the rebar to create
the pool or spa shell, usually 4 to 5 inches thick for walls, 6
inches on the deep end floor, and 1 1 inches for the bond beam. Like
spraying water from a garden hose, some waste, splashing, and
overspray occurs.
Some of the gunite does not adhere to the rest
of the mix and falls away from the surface being sprayed. This waste
is called rebound and should be cleaned up and thrown away. Some
builders use it to fill in step, love-seat, or other contour areas.
This is a poor practice because rebound hardens quickly and when it
is used as filler it creates air pockets, which later settle and
cause leaks. This is why a large percentage of cracks and leaks are
found on or near pool steps. In a vinyl-lined pool, this gunite
process will instead be the installation of the panels that form the
shell.
Tile is added, usually at the waterline to
create an aesthetically pleasing finish and to provide a material at
the surface (where oil and scum accumulate) that is not porous and
is therefore easier to clean. Sometimes decorative tile patterns or
racing lanes are installed to match the tile surface line.
Of course, the entire pool can be tiled. I
have serviced several such pools, and although the original cost is
high, I can enthusiastically recommend this design. An all-tile pool
is strikingly beautiful, holds a pH better than plaster pools, never
needs refinishing, and does not stain or etch.
Rock, brick, or stone brought to the edge of
the pool, or in some cases over the edge and below the waterline,
create unique designs and natural pond looks. Until a few years ago,
rocks were trucked in and cemented in place around the pool.
Unfortunately such shipping and installation was very expensive and
the bond beam needed extra, costly reinforcement to support the
weight.
Since the late 1980s, however, rocks are
formed with light rebar or chicken wire sculpting, then covered with
a special plaster, concrete, and sand mix colored to look like
natural rock. Made on-site, such artificial rock is made to conform
exactly to design specifications and is far cheaper and lighter than
real rock. Rock, slate, and waterfalls are added using Thoroseal (a
waterproof concrete sealer) to set them in place.
The only drawback to these and natural rock is
that they are porous and you will soon see unsightly white scale
forming at the waterline. Even if you maintain perfect chemistry in
the pool, natural evaporation leaves behind any mineral present in
the water as scale, which appears as white scum, mostly calcium,
around the waterline. Although this can be scrubbed off of nonporous
tile, it must be sandblasted off rocks and will reappear in short
order. One solution is to keep a constant water level, replacing
water as it evaporates so the scale line is hidden under the
waterline. Of course, maintaining proper water chemistry balance
also reduces scale.
Coping is the finish work done to the top of
the pool wall, usually attached directly to the bond beam. Coping
stones are often precast and made of porous material to provide
better traction for the wet feet and hands of swimmers entering or
leaving the pool.
After the coping is laid on, the deck is
poured (or deck brick or stone work is done) up to the edge of the
coping, leaving a 1/4 to 1/2 inch gap. The gap, which allows
expansion or contraction of the deck and coping materials in hot and
cold temperatures, is filled with silicone caulking to keep out
water. All of this work should be done before plastering or finish
work, because it is usually the messiest procedure. I have seen
builders forced to drain and replaster newly finished pools because
they completed the pool before the deck work was done, only to find
sloppy deck workers scatter the fresh, soft pool plaster with
cement, gravel, and stone chips. |
