Lennox Head 03539: Pool Restoration

A pool surface described as hollow or drummy makes a noticeably different sound when lightly tapped because the render, plaster, Pebblecrete, Marblesheen or earlier levelling layer may no longer be fully bonded to the concrete shell. The surface can still look intact, so tapping is only a screening check; it does not show the full boundary or cause. The empty pool should be systematically surveyed, with loose areas opened back to sound material so moisture, cracks, contamination and movement in the substrate can be assessed before resurfacing.

A fine hairline crack is not automatically structural, but its width alone does not determine the risk. Location, depth, direction, displacement, moisture, surrounding soundness and whether it is growing are all important. Fine crazing may be limited to the surface, while a crack through the shell can admit water or indicate movement. Photograph and mark the crack so changes can be monitored, and arrange an assessment if it is widening, leaking, recurring through repairs or associated with movement.

Pool stain colour alone does not confirm the cause. Brown or rust-coloured marks may involve iron or organic debris; green, grey or black marks can involve algae, copper, manganese or material trapped in a rough surface. Location, texture, recent water changes and the way a small test area responds are more useful than colour by itself. The source also needs attention, such as metals in fill water, corroding equipment, poor circulation or debris, otherwise the stain can return after cleaning.

Ongoing water loss, damp ground, staining, water movement at the crack or a bucket test that confirms abnormal loss can indicate leakage, although the actual source may be elsewhere. Structural concern increases where the crack is displaced, widening, repeated through an earlier repair or accompanied by settlement, bowed walls or movement at steps and fittings. Neither condition can be confirmed from a photograph alone. Leak testing and inspection of the surrounding shell are used to determine whether lining repair, plumbing work or structural investigation is required.

Many stains can be treated without resurfacing when the underlying finish is sound and the stain type is correctly identified. Organic, metal and mineral deposits require different treatment approaches, so the safest starting point is water testing and a controlled test on a small area. Resurfacing becomes more relevant when stains are deeply embedded, repeatedly return through a porous surface, or occur with widespread roughness, pitting, peeling or earlier failed repairs. Correcting the stain source remains important after either treatment.

A local repair may be suitable where the hollow area is clearly contained and the surrounding finish remains sound and firmly bonded. If drummy areas are widespread, recurring, soft or connected by cracking, progressive removal may show that a broader section—or the existing finish—needs to be taken back to the concrete shell. The decision is made after the pool is emptied and the surface is tap-tested. Unstable material must not be left beneath a new lining. Where older Marblesheen could contain asbestos, testing and compliant removal planning are required before it is disturbed. The exposed base is then repaired and levelled before resurfacing.