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Preparing the pool shell for an exposed-aggregate finish
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What needs to be right beneath and around a pool before an exposed-aggregate finish goes on, plus a simple acceptance checklist for architects, pool builders and developers in hot climates.
An exposed-aggregate finish needs a sound, accepted base, professional application and appropriate water care. Before the applicator arrives, the shell, render and specified waterproofing should be accepted and recorded. Cracks should be investigated, fittings set for the finished thickness, and the pool, tanks and surroundings cleaned. The finishing visit also needs an agreed plan for weather protection and a steady supply of tested, suitable filling water, because PebbleCrete finishes cure under water and the pool must be filled promptly.
Where the finish sits in the pool
It helps to read a finished pool as four layers, each with its own responsibility:
- Pool water: you always see the finish through it.
- Exposed-aggregate finish: the decorative surface. PebbleCrete finishes have a nominal thickness of 10 mm.
- Bond coat: the method statement sets the bonding requirements, and the project team accepts them. A bond coat is required on renovations. For new pools, follow the method statement.
- Prepared watertight base: the structural shell, render, levelling and waterproofing.
The finish gives the pool its colour and texture, but its shape follows the base. Wall alignment, falls, step shapes and level corrections all belong to preparation. A finish applied over weak render, contamination or an incompatible layer can fail even when the finishing material itself is sound. The finish is decorative. It is not structural repair and it is not waterproofing.
Shell and render condition
The surface receiving the finish should be sound and clean, and it should be agreed in advance. Weak, hollow or detached render must be dealt with before it is covered. A simple first check is to tap across the walls, floor and steps and listen for a hollow sound.
A renovation starts with an inspection. An old tile or plaster surface that is still attached in places is not automatically a suitable base everywhere. The contractor should state in writing what will be removed, repaired, kept and tested. That way, nobody mistakes a finishing quotation for a full renovation price.
Cracks and exposed reinforcement
Cracks need investigating, not just filling. Find out what caused each crack and whether it is still moving. Then make sure the repair or joint detail responds to what you found. Rust spots or exposed steel can indicate a problem beneath the surface, so investigate them before anything is covered. No single repair material suits every case, and a decorative finish will not hold a moving crack closed.
Waterproofing is a separate, agreed scope
The project specification should state:
- how the pool will be made watertight
- who is responsible for it
- that the waterproofing system is compatible with the finish
Complete the specified waterproofing and water test at the stage the pool designer sets. Record acceptance before the waterproofing is covered.
Never treat a decorative finish as the fix for an unexplained leak. If a pool is losing water, find the cause first by checking the structure, pipework, joints and penetrations.
Fittings, levels and clearances
The finish adds thickness to every surface, so check dimensions against the finished levels, not the bare shell. Before the finishing visit, confirm that:
- lights, inlets, drains, sumps and grilles will sit correctly once the finish is in place
- covers and gratings will still fit their frames
- the levels of overflow edges, waterline tiles and coping are coordinated with the design operating water level
- step treads, risers and any contrasting step markers have been agreed as one design
- cable routes for lighting and other services, and service access, are fixed and recorded
A grating that no longer fits after finishing is an avoidable and very visible defect.
Cleanliness and site readiness
Finish any dusty or heavy work nearby before the application date. This includes overhead work, cutting, earthworks and deck installation. Plan how the new surface will be protected from later debris, knocks and chemical spills.
Remove timber, steel offcuts, tools and rubble from the pool. Clean the balance tanks, sumps, channels and pipework too, because debris left there can come back once filling and circulation begin.
Check that the circulation equipment works and that suitable filling water is available. Clear-looking water is not proof of quality, so test the source and check the storage tanks and delivery hoses. Some sources may be acidic, including well, river or lake water in parts of Southeast Asia. Test to confirm a source is suitable, and agree any treatment as part of the start-up plan.
Stage acceptance before the finish
The responsible party should accept each layer before the next one covers it. Agree and record:
- Condition: the accepted substrate, any repairs and the water-test result, with dated photographs.
- Dimensions: finished levels around fittings, steps, waterline and coping.
- Readiness: site work complete, water supply and equipment ready, and a named start-up operator.
Before work begins, obtain PebbleCrete’s current Method Statement and Substrate Acceptance Protocol for the agreed system (available on request). Confirm that the applicator is working to the latest revision.
PebbleCrete supplies the material and the technical documents, and professional applicators carry out the work. Unless agreed otherwise in writing, the application, the mock-up and the finished result are the responsibility of the owner and their applicator. Name in writing who is responsible for the substrate, waterproofing, the locally bought white Portland cement, application and start-up.
Before work starts, have the applicator make an on-site mock-up. Approve it against a current physical sample viewed wet.
Hot climates: timing, protection and filling
Heat, sun, wind and sudden rain can all affect application conditions and the programme. Agree a weather, protection and filling plan with the applicator, in line with the current method statement:
- Timing: agree the start time with the applicator. Check the forecast and decide in advance when work will be postponed.
- Sun and wind protection: arrange shade, covers and windbreaks as the applicator requires.
- Rain protection: have covers ready, and agree in advance what happens if a storm arrives during application.
- Water supply: confirm how much water is available and how fast it flows, so the pool can be filled without long pauses. If you need tanker deliveries, book them ahead, and test tanker water like any other source.
- Prompt filling: once the applicator releases the pool, start filling promptly and keep going without interruption. PebbleCrete finishes cure under water, so a newly finished pool should not be left standing empty in the sun.
After filling, the agreed start-up programme sets out circulation, brushing and water testing.
A simple acceptance checklist
| Check | Accepted | Accepted by / date |
|---|---|---|
| Shell and render sound, with no hollow, weak or detached areas | ☐ | |
| Cracks investigated; repair detail agreed and completed | ☐ | |
| Exposed steel or rust spots investigated and repaired | ☐ | |
| Specified waterproofing completed, water-tested and acceptance recorded | ☐ | |
| Fittings, covers and drains checked against the finished thickness | ☐ | |
| Waterline, coping, overflow and step levels agreed | ☐ | |
| Nearby dusty or heavy work finished; protection planned | ☐ | |
| Pool, tanks, sumps and channels clean | ☐ | |
| Circulation equipment working | ☐ | |
| Filling-water source tested; tanks and hoses clean | ☐ | |
| Weather, protection and filling plan agreed with the applicator | ☐ | |
| Current Method Statement, Substrate Acceptance Protocol and responsibilities confirmed | ☐ | |
| Physical sample (viewed wet) and on-site mock-up approved | ☐ | |
| Start-up operator and programme agreed | ☐ |
Photograph the prepared pool and keep the signed checklist with the handover records.
In Thailand: Pebble Pools (pebblepools.co.th), a separate company, offers leak repair and waterproofing and pool inspection. Their local guide: pool leak or evaporation?
Frequently asked questions
How should a pool shell be prepared for an exposed-aggregate finish?
Have the shell and render inspected and any weak, hollow or detached areas repaired; investigate cracks and exposed steel; complete and water-test the specified waterproofing and record acceptance; set fittings, covers and levels for the 10 mm finish build-up; clean the pool, tanks and pipework; and agree the filling-water supply, weather protection and start-up programme with the applicator before the finishing visit.
Can the finish seal a pool that is leaking?
No. The finish is decorative and does not replace waterproofing or structural repair. Find and fix the cause of the water loss first, then water-test and record acceptance.
Why must the pool be filled so soon after finishing?
PebbleCrete finishes cure under water. Filling promptly and without interruption protects the new surface, which matters even more in strong sun and heat. After filling, follow the agreed start-up programme.
Can an existing tiled pool be finished over directly?
Not without an inspection, and an inspection on its own does not mean the tiles can stay. That depends on the assessed substrate and the approved system. The inspection and the Substrate Acceptance Protocol decide what, if anything, can remain. Loose, hollow or deteriorated layers must be removed, and a bond coat is required. The contractor should set out the preparation scope in writing before the finish is priced.
Photographs and screen colours are illustrations. Confirm colour and texture with a current physical sample viewed wet and an approved on-site mock-up.
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This article provides general technical guidance, not a design, installation or safety instruction for a specific pool. Every project depends on its structure, substrate, waterproofing, water conditions and local regulations. Refer to the current PebbleCrete technical documents: the Technical Data Sheet and the Installation Overview are available online, and the Safety Data Sheet and the full Method Statement are issued on request. Confirm structural, waterproofing, electrical and installation decisions with qualified professionals. PebbleCrete supplies the material only; unless agreed otherwise in writing, substrate preparation and application are carried out by the owner’s applicator, who is responsible for that work. Nothing in this article limits your statutory rights.