Renovating an older pool without rebuilding the shell

A practical guide for architects, pool builders and hospitality developers to assessing an existing concrete pool shell, preparing old tile or plaster, planning low-season works and changing to a continuous exposed-aggregate finish.

You may be able to renovate an existing tiled or plastered concrete pool without demolishing the structure. This depends on a qualified contractor physically assessing the pool and finding the shell, and any layers you plan to keep, suitable. The new exposed-aggregate finish then goes over an accepted, prepared base and a bond coat. The finish is decorative. It is not a structural repair or waterproofing, so leaks must be diagnosed, weak layers dealt with, cracks assessed and fitting clearances checked before finishing starts.

Assess the existing shell first

A decorative finish is only as sound as the construction beneath it. Before you treat a finishing quotation as a complete renovation budget, ask a qualified contractor to inspect the empty shell and record the following:

• Cracks and structure: the cause of each crack and whether it is still moving. Exposed reinforcement or rust staining must be opened up and diagnosed. The agreed repair or movement-joint detail should deal with the cause, not just bridge over it.
• Leaks and waterproofing: PebbleCrete does not replace structural repairs or the waterproofing the project requires. It must never be used to cure an unexplained leak. Inspect the shell, pipework, expansion joints and penetrations, and repair whatever is causing the leak. Complete the specified waterproofing and water testing, and record formal acceptance before the base is covered.
• Geometry: the finish, applied at a nominal 10 mm, gives the pool its colour and texture, but it follows the shape of the prepared base. Correct wall plumb, floor falls towards the main drains and step profiles during rendering, not during finishing.
• Fittings and clearances: measure skimmers, overflow channels, underwater lights, inlet fittings and floor drain grilles against the planned build-up. Covers, light rings and step markers can then be set to the agreed finished levels.

What to do with old tile, grout and plaster

On an ageing tiled pool, the grout and tile bedding usually fail before the tile does. Grout erodes, mineral deposits build up along the waterline and individual tiles come loose. Older plastered or painted pools may show etching, chalking, blistering or patches of delamination.

The contractor starts with a sounding survey, tapping across the floor, walls and steps to find hollow-sounding or loose layers. Tile or render that is firmly attached in one area is not automatically a suitable base for the whole pool. The findings lead to one of two preparation paths:

• Full or partial removal: loose tiles, failed bedding, contaminated plaster and hollow render are removed back to sound concrete. This is followed by surface repair, re-rendering to restore levels and waterproofing as required.
• Preparation over a sound existing surface: this applies where the contractor confirms that the existing layer is well bonded, structurally sound and compatible with the specified bond coat and finish system. The surface is then prepared and cleaned to receive the new build-up.

Every refurbishment needs a bond coat between the prepared base and the new finish. It is not optional. Ask for the preparation scope in writing, covering what will be removed, repaired, kept and water-tested. Record it using PebbleCrete’s Substrate Acceptance Protocol (available on request), with a named party accepting the substrate.

Planning works in a hotel low season

Hotels, resorts and villa estates in Southeast Asia and the Middle East usually have to take a feature pool out of service in the low or shoulder season. Delays can happen when hidden substrate faults are found after removal starts, or when site contamination holds up the finishing crew. Plan five stages early:

1. Separate the renovation and finishing scopes. Name who is responsible for demolition, structural repairs, waterproofing, rendering, mechanical and electrical (M&E) equipment upgrades, material supply, application and start-up water care.
2. Order materials and approve samples early. PebbleCrete colours are batched to order in Phuket and supplied as a dry blend in sealed 25 kg bags. White Portland cement is sourced locally and separately, so agree who supplies each component. One bag covers about 1.8 m² at a nominal 10 mm. This is measured across the actual surface of walls, floors and steps, not the plan water area. Coverage is a planning figure, so confirm quantities and batch planning against the measured finish area.
3. Complete surrounding heavy works first. Finish deck cutting, pergola repairs, landscaping and overhead painting before the application visit. Clean out balance tanks, sumps and pipework so that construction silt is not pumped back into the new finish.
4. Prepare for prompt filling. Once the finish is applied and the applicator releases the pool, filling starts promptly and continues without a break, because the finish cures under water. Test the filling water well before the application date, as borewell, river or lake water can have a pH as low as 5.5 or carry dissolved metals. Check storage tanks and delivery hoses too, and keep the results for the handover record.
5. Allow for the start-up month. Clear water is not necessarily balanced water. While the surface continues to cure, run filtration continuously, brush the whole pool daily and monitor the water chemistry closely. PebbleCrete’s care targets are a pH of 7.6–7.8, total alkalinity of 80–120 ppm and calcium hardness of 200–400 ppm. Follow the start-up programme issued for the pool, which sets out the full routine and parameter ranges. If the pool uses salt chlorination, wait 28–30 days after filling before adding salt. Never add chlorine directly onto the finish. Dose it into the balance tank or, if there isn’t one, the skimmer.

Reopening should follow an agreed handover and operating acceptance. The first-month programme is not a reopening timetable.

What changes visually when grout lines disappear

An exposed-aggregate finish is applied as a continuous layer, with movement joints where the design needs them, so the interior reads as one shaped basin rather than a grid. Curved steps, sun shelves and freeform lagoons read as continuous surfaces, with no tile grid to set out around the curves. On large resort pools and lagoons, discuss joint layout and batch planning early with the designer responsible for the project.

The edges and transitions still need careful detailing:

• Step edges: contrasting step markers help swimmers see step edges under moving water.
• Waterline and overflows: the waterline is repeatedly wetted and dried and collects deposits. A renovation can pair the exposed-aggregate interior with an easy-to-maintain band of pool-suitable tile beneath the coping. Another option is a polished aggregate band, subject to approved samples and agreed cleaning requirements.

Choosing a finish family

PebbleCrete Classic combines natural aggregate, glass crystals or both, with limited glass-bead accents, for a quiet, mineral look. PebbleCrete Supreme may combine natural aggregate, glass beads and glass crystals, depending on the blend, for noticeable sparkle under moving light. PebbleCrete Glass uses glass beads throughout, so its appearance changes with sunlight and depth.

Water depth, sky reflections and lighting all change how a surface looks underwater. View current physical samples wet in the pool’s actual surroundings, and ask the applicator to prepare an on-site mock-up panel to set the acceptance standard. Natural stone and glass applied by hand vary slightly from batch to batch, so treat the panel as a reference rather than an exact match. PebbleCrete supplies the material and technical support. Application and the finished result are the responsibility of the owner and applicator unless agreed otherwise in writing.

As a planning figure, an exposed-aggregate pool finish is generally expected to serve for 15–20 years. This is an industry estimate, not a warranty term. Where an individual pool falls within or outside that range depends on substrate preparation, application quality, water chemistry and routine maintenance.

In Thailand: Pebble Pools (pebblepools.co.th) offers pool inspection with a written report and leak repair and waterproofing. Their local guide: does resurfacing stop a pool leak?

Frequently asked questions

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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