Tiling pool tanks
CONSTRUCTION & TESTING
- Pool tanks are generally constructed as follows:
- Reinforced concrete blocks or reinforced patent blockwork + cement: sand render
- Reinforced concrete within a cavity wall construction
- Cast reinforced concrete
- Gunite/shotcrete (pneumatically applied concrete)
The watertightness of the pools shell must be tested before the application of the render, screed and tile finishes, as per British Standard BS 8007: 1987 Section 9.2 which states:
“The structure should be cleaned and initially filled to the normal maximum level with the specified liquid (usually water) at a uniform rate of not greater than 2m in 24 hours.
When first filled, the liquid level should be maintained by the addition of further liquid for a stabilising period while absorption and autogenous healing take place. The stabilising period may be 7 days for a maximum design crack width of 0.1mm or 21 days for 0.2mm or greater. After the stabilising period the level of the liquid surface should be recorded at 24h intervals for a test period of 7 days. During this 7 day test period the total permissible drop in level, after allowing for evaporation and rainfall, should not exceed 1/500th of the average water depth of the full tank, 10mm or another specified amount.
Should the structure not satisfy the 7-day test, then after the completion of the remedial work it should be refilled and if necessary left for a further stabilising period; a further test of 7 days duration should then be undertaken in accordance with this clause.”
It should be noted that when using reinforced concrete blocks and/or patented blockwork, the rendering forms part of the watertight construction and should be included in the above test.
Pool tanks that are out of the ground need particular attention in the design stages particularly if they are constructed/installed on upper floor levels.
The minimum time intervals between stages of the work are:
- Completion (curing) of pool shell to start of rendering/screeding/tiling—6 weeks
- Completion of rendering/screeding to start of tiling—3 weeks
- Completion of tiling to start of grouting—3 days
- Completion of grouting and sealing of movement joints to filling of pool—3 weeks
Longer periods may be required in wet weather.
Filling, emptying and heating pool: Minimise stresses.
- Maximum filling and emptying rate—750mm/24 hours
- Maximum rate of heating water—0.25°C/hour
Must have a low water absorption of 3% or preferably less. Suitable tile classifications are:
- Extruded type AIa or AIb—BS EN 14411
- Dry pressed type: Bia or B1B—BS EN 14411
Product suitability should be obtained by the tile manufacturer.
Loose or hollow portions must be cut out and repaired. All dusty or porous substrates should be thoroughly dry brushed prior to priming with Norcros Prime Bond diluted 1:4 with water. Allow to dry.
Fix the tiles using Norcros One Part Flexible Adhesive or Norcros Standard Set Flexible S1 Adhesive.
Gradually add 20kg of One Part Flexible powder to 5.5– 5.7 litres of water and mix to a thick, creamy, slump-free consistency. Mix only enough material that can be used within the pot life of the product (around 4 hours).
Apply the adhesive using a suitable notched trowel held at a 45° angle to form parallel ribs into which the tiles should be pushed with a firm twisting action to produce a 3-6mm thick solid, void-free bed beneath the tiles. Work in small areas and discard any adhesive that begins to dry or skin over. Tiles with deeply keyed back profiles may need to be back buttered. Every so often lift a tile to check that it is in full contact with the adhesive and that no voids are left in the adhesive bed. Wipe off any adhesive residues from the surface of the tiles using a damp sponge before the adhesive sets. Remove deposits of adhesive which may build up in the gaps between the tiles. DO NOT TRAFFIC THE TILES FOR AT LEAST 18-24 HOURS or until the adhesive has set.
Allow the adhesive to dry for a minimum of 3 days before grouting commences.
Allow the adhesive to dry.
In hard water areas (>200mg/l (CaCO3) a cement-based grout such as Norcros Stop Mould Flexible (BS EN 13888 CG2) may be used.
In soft water areas (<200mg/l (CaCO3), hydrotherapy pools, salt water pools or where wave machines etc. are to be used, it is essential that an epoxy resin grout such as Norcros Super Epoxy (BS EN 13888 RG1) is used.
Clean out any dirt, dust or adhesive from between the tiles and ensure that the joints are dry before grouting commences.
In accordance with British Standard BS 5385: Part 4 movement joints should be incorporated as follows:
- In the pool lining around the perimeter at the junction of the bottom and sides
- At vertical corners and at any change of plane in the bottom.
- If joints between tiles are less than 6mm it is advisable to insert additional movement joints down the pool sides and across the bottom in a continuous loop at 6m intervals or less to suit design considerations.
- Movement joints should coincide with the structural junction of the pool shell and the surround slab and where tiling abuts walls, drainage channels and other features.
- Intermediate movement joints should be inserted at intervals of 6m or less.
- Allow 3 weeks following grouting and sealing before filling the pool.
Norcros One Part Flexible—Approximately 4-5kg/m² based upon a 3-4mm solid bed
Norcros Standard Set Flexible S1— Approximately 3-4kg/m² based upon a 3-4mm solid bed.
Norcros Stop Mould Flexible Grout—Approximately 0.6kg/m² based upon a 250mm x 125mm x 8mm tile with a 3mm wide joint or 1.1kg based upon a 25mm x 25mm x 4mm mosaic with a 2mm wide joint.
Norcros Super Epoxy– 0.5kg/m² based upon a 250mm x 125mm x 8mm tile with a 3mm wide joint or 1kg/m² based upon a 25mm x 25mm x 4mm mosaic with a 2mm wide joint.
The following formula may be used to calculate the approximate grout coverage:
(Tile Length (mm) + Tile Width (mm) x Tile Thickness (mm) x Joint Width (mm) x S.G = kg/m2
(Tile Length x Tile Width)
S.G = 2.0 No Mould Flexible; 1.6 Easy Clean Epoxy
All measurements MUST be in mm. Always allow 10% for wastage