Vince Ruffini, ARDEX contract manager elaborates on the technical considerations to think about when it comes to grouting swimming pools
GROUTING in swimming pools is far more than a finishing touch – it’s a critical component that ensures durability, hygiene, expansion and aesthetic integrity in one of the most aggressive environments for tiling systems.
Pools expose grout to constant immersion, chemical treatments, thermal cycling, and mechanical stress. A poorly considered grout specification can lead to failure, staining, or costly repairs.
This article explores the key considerations before grouting swimming pools, drawing on best practice guidance from BS5385, BS8007, and industry standards.
Water chemistry: pH and balance
Pool water must be chemically balanced to protect grout and adhesives. The ideal pH range is 7.2–7.8.
Low pH (acidic): Aggressive water dissolves calcium salts in cement-based grouts, leading to erosion and loss of bond.
High pH (alkaline): Promotes scaling and mineral deposits on grout joints.
Unbalanced water accelerates deterioration, so grout selection should consider the likelihood of aggressive conditions. In soft water areas or pools with complex water features, reaction resin (epoxy) grouts are recommended for their impervious nature and chemical resistance.
Water hardness and quality
Soft, acidic water is ‘hungry’ for calcium and will leach minerals from cement-based grout, weakening its structure. Meanwhile, hard water is full of calcium salts, and will deposit these salts, causing efflorescence and surface scaling.
Testing water hardness before specification is essential. Where calcium levels are below 250 mg/litre, epoxy grout is strongly advised. For balanced water and normal cleaning regimes, highly polymer-modified cementitious grouts can perform well.
Maintenance and cleaning regimes
Swimming pools demand rigorous cleaning schedules, often involving aggressive chemicals and high-pressure washing. Cement-based grouts are suitable for balanced hard water and standard cleaning.
Epoxy grouts are impervious, stain-resistant, and ideal for areas exposed to intensive cleaning or chemical attack. It’s important to educate clients on maintenance: improper cleaning agents can damage grout, even epoxy types.
Pool location and environmental factors
Consider pool location and environmental factors when selecting your grout. Indoor pools are situated in a more controlled environment, but high humidity can affect background substrates.
Outdoor pools are subject to temperature changes and UV exposure that can fade pigments; specify UV-stable grout and protective coatings. Coastal pools are exposed to salts and demands salt-resistant grout formulations.
Climate and exposure dictate grout durability – always consider freeze-thaw cycles for exterior installations.
UV resistance
Ultraviolet radiation impacts grout colour stability and polymer integrity. For outdoor pools, select UV-stable grout systems and sealers to maintain aesthetics over time.
Durability under dynamic conditions
Pools are not static environments. Features such as jets, waterfalls, wave machines, and hydrotherapy systems create constant mechanical stress. Grouts must withstand abrasion from moving water and erosion at waterline areas. Epoxy grouts excel in these conditions.
Thermal and chemical resistance
Pools undergo frequent chemical dosing and temperature changes. Grout must resist chlorine, bromine, and other sanitisers without degrading. Thermal cycling from heated pools or seasonal variations can cause expansion and contraction-select grouts with deformability and high bond strength.
Grout selection: cementitious vs. epoxy
Cementitious Grouts (BS EN 13888 CG classification) include
– CG1: Standard cement grout
– CG2WA: Improved cement grout with reduced water absorption and high abrasion resistance
– Best for balanced hard water and ancillary areas
– Reaction resin grouts (Epoxy grouts) (BS EN 13888 R classification)
– Impervious, chemically resistant, ideal for aggressive water, soft water areas, and high-abrasion zones.
Best practice installation
When fixing and grouting consider the minimum joint widths. BS-5385 recommends 2mm for walls, typically mosaic, 3mm for floors, 5mm for large format Butt-jointing is not acceptable.
Solid-bed fixing should also be strived to achieve so far as is practically possible with 100% adhesive coverage behind tiles to prevent voids and water ingress.
Movement joints should be incorporated as per BS5385 Part 4 at changes in plane, perimeters, 6m intervals and stress concentration points.
Grouting swimming pools requires a holistic approach: understanding water chemistry, environmental exposure, mechanical stresses, and maintenance regimes. By considering pH, water hardness, UV exposure, durability, and dynamic water movement, and by selecting the correct grout type-cementitious or epoxy-you can deliver a specification that ensures longevity, safety, and visual appeal.
ARDEX • www.ardex.com
