Pool Excavation Process: The 6 Stages From Set-Out to Shell Placement

Pool excavation is the staged site work that cuts the hole a fibreglass pool shell is lowered into. It involves more than digging a hole. The site supervisor marks the pool footprint out from the engineering plan, and the excavator then cuts the void to the exact shape of the shell plus working room. The same dig goes slightly wider and deeper than the shell itself, keeps the base dead level, and gets the spoil off the site. Those actions follow a typical order, from set-out through the bulk dig, levelling, spoil removal and a final clean up. This page covers pool excavation for a residential fibreglass pool project in South East Queensland.

What does pool excavation produce?

Pool excavation produces a pool hole cut to the predetermined specifications for the pool going in. A fibreglass pool shell arrives pre-moulded and has to fit the excavation exactly, so the hole is cut to suit the shell. The excavator digs off the dimensions on the engineering plan, and the result is a well-defined, accurately sized void with room to work around the shell once it is in the ground.

What are the stages of pool excavation, in order?

A pool dig on our sites breaks into six stages. The order below is the sequence a residential dig follows. It is a typical order, not a fixed industry standard, and a difficult block can change how long any one stage takes.

The six stages of a pool excavation, from setting out the footprint to the final clean-up. The order shown is the one a residential dig usually follows on site, not a fixed industry standard.

Set out the pool footprint. Before machinery starts, the site supervisor marks the pool footprint on the ground from the engineering plan. The marked lines fix where the shell sits and where the dig begins. Underground services are located at the same time, because sewer, stormwater, power and gas runs can cross the footprint. On our jobs the mark-out is a scheduled task of its own, set about a week ahead of the installation date. Front-yard installs get closer attention at this point, since underground services are usually more prominent in a front yard than in a backyard.
Cut the void to the shell shape plus working room. The excavator cuts the void to the shell's exact outline, with working room left around it. The pool hole is excavated with the excavator according to the predetermined specifications, so its length, width and depth follow the plan. Accuracy is worth the time here, because a pre-moulded shell has to fit the excavation exactly.
Dig deeper and wider than the shell's final depth. Pool excavation requires the hole to be dug deeper than the pool shell's final depth. The extra depth leaves space for the bedding layer underneath the pool, for plumbing, and for backfilling. The void is cut slightly wider than the shell for the same reason, so backfill can be placed around the sides. What the dig has to do to reach those dimensions depends on the ground it goes through. Expansive soil makes over-excavation necessary. On a sloping or uneven site, stepped excavation or a retaining solution is typically needed before a stable, level base can be cut. Where groundwater sits at excavation depth, dewatering is required, and it adds time to the dig.
Trim the base dead level. Keeping the base dead level is part of the dig itself. The operator trims the floor of the excavation to the finished depth and takes out soft spots as they appear. The base is what the shell is bedded and set on, so the accuracy of the trim carries through into how the pool finishes.
Clear the spoil as the dig progresses. On our jobs excavated material leaves the site as the dig progresses. Carting happens alongside the digging, which keeps the area around the hole clear and the workspace safe for the crew. Spoil leaves in tipper loads, and each load carries a disposal fee at the tip. How it gets from the hole to the truck depends on the access width on the block.
Clean up the excavation. The dig finishes with a clean-up, the last stage in the excavation process. The stage is done when the hole is clear of the loose dirt and rock the digging piles up around the edge, and the walls and floor are trimmed back to an even face. Clearing it straight away keeps the site workable for the pool installers, and an even excavation is what lets the swimming pool sit properly on a level base.

What machinery does a pool dig run on?

Our own excavation line is built from four elements: a digger, a bobcat, a tipper, and the dump fees for the loads the tipper carries. The digger is a 3.5 to 6 tonne excavator on a standard site, and a mini excavator where access is tight. The bobcat carts spoil from the hole to the tipper, and the tipper takes it off site.

Which of those machines can reach the pool site is decided by site access, because the minimum width from the kerb to the hole sets the plant size. Access also governs how the machinery path is prepared before the dig, and how the spoil gets from the hole to the truck where a bobcat cannot fit down the side.

When is pool excavation scheduled relative to the installation date?

Excavation sits close to the installation date in the build program, and its position there is part of how long a fibreglass pool installation takes. On our schedule the dig starts two days before the shell installation, and the site mark-out sits about a week before that installation date. Excavation should not occur more than about two weeks before the planned installation date. A hole left open longer than that is exposed to excessive rain and to unstable soil, either of which can force re-excavation before the shell goes in. Booking the dig close to the install also keeps the tasks that hang off it together. The first gravel delivery starts with the excavation, and an eight-week temporary safety fence hire goes up around the open hole.

How long does pool excavation take, and what extends it?

Our own program allows one day for the excavation task on a standard residential dig. The same work is also put at around a day for an experienced and skilled contractor on a standard-sized home pool. Complicated and larger pools may take a bit more time than that. Where the diggers strike rock, or the ground proves unstable, digging time can increase further again. A figure of a few days to a few weeks is also quoted for pool excavation. That range appears to measure something broader: the whole excavation phase across pool size, access difficulties, soil type and weather.

Constraint or delay factor	Effect on excavation timing	Reason or guidance
Excavating more than about two weeks before the planned installation date	Outside our booking window	Excessive rain or unstable soil in the intervening weeks can force re-excavation
Rock struck during the dig	Digging time can increase beyond about a day	Rock is slower to dig than soil and usually costs more
Soil instability	Digging time can increase beyond about a day	Both the soil test and the site audit run before the dig is booked
Complicated or larger pool	Digging time can increase beyond about a day	More material to move, and more shape to cut to the plan

What happens after pool excavation, and when is the fibreglass pool shell placed?

The bedding layer goes into the cleaned hole, and the fibreglass pool shell is set down onto it. The shell is placed by crane once the excavation is complete on about two in three of our installs, so the hole and its base have to be complete on the day the crane and the delivery truck arrive. A delay in the dig moves the crane booking with it. Backfilling and the underground plumbing follow once the shell is seated on the base.

FAQs

How much bigger is the pool hole than the pool shell?

The pool hole is cut slightly wider and slightly deeper than the fibreglass pool shell's finished dimensions. The extra depth carries the bedding layer the shell sits on and leaves room for the plumbing, and the extra width leaves room to backfill around the sides. That allowance is part of the predetermined specifications the hole is dug to, so it comes off the engineering plan for the pool model going in.

Where does the dirt from a pool excavation go?

The excavated material, called spoil, is trucked off site. A bobcat carts it from the hole to the tipper, and each tipper load carries a dump fee at the tip. On our jobs the spoil leaves as the dig progresses, so it does not stand in a pile beside the hole waiting for the end of the job.

Will excavation machinery fit through a standard side gate?

The answer turns on the narrowest point between the kerb and the pool site, which is the measurement site access is assessed on. That width decides which machine can reach the dig, and a tighter opening moves the work onto smaller plant. The plant on a quote is sized from that single measurement, so the gate is worth measuring before the site visit.

What happens if the pool dig hits rock?

Digging into rock takes longer than digging soil, and it usually costs more. Rock is usually factored into the quote, so the allowance is priced before the machine arrives on site.

If you want a read on how your block digs, call us on 1300 30 60 11.