Bathrooms & Wet Areas

Bathrooms and wet areas are the bathrooms, ensuites, showers, toilets and laundries in homes and apartments. Functionally they must contain water, remove moisture, deliver safe hot water, drain properly and stay hygienic. Their most important component is one nobody sees: the waterproofing membrane under the tiles and behind the shower walls. Wet area leaks are among the most common and costly defects in residential buildings, especially apartments, where a failed shower floods the unit below and damages structure for years before it shows.

Era is a strong guide. Many bathrooms built before the 1980s have no membrane at all and rely on tiles and grout; later bathrooms have membranes of varying quality; current standards demand membranes with continuous upturns, flashing at thresholds, and floors falling to the waste. Timber-framed floors move and crack tiles and membranes more than concrete.

What shortens fitness for purpose:

• Poor membrane installation: thin coats, unreinforced junctions, membranes stopped short at walls and doors, and wastes without puddle flanges.
• Substrate movement in timber floors and lightweight walls cracking tiles and membranes.
• Hobless showers without adequate falls and waterstops, letting water flow across the floor.
• Neglected sealant at junctions and around screens.
• Weak or unused exhaust leaving moisture in the room.

Membrane failure

Water reaches the substrate through gaps in the membrane at wall-floor junctions, around the floor waste, at the shower entry and threshold, and where taps, mixers and pipes penetrate the wall. Grout and tiles are not waterproof; once the membrane fails, every shower soaks the substrate. In apartments water travels along the slab and appears in the ceiling below or in adjoining rooms, sometimes metres away.

Threshold and waterstop failure

At bathroom doors and shower entries, water flows along the floor or wicks under the tiles beyond the wet area. Missing or poorly sealed waterstop angles let water reach skirtings, carpets and timber floors outside the bathroom, which swell and rot.

Inadequate falls

Floors that do not fall to the waste, or fall the wrong way, leave water ponding against walls and doorways and push it toward weak points in the membrane.

Plumbing leaks

Leaking mixer bodies and connections inside walls, toilet pan seals, cistern connections, bath wastes and pipe joints leak constantly, unlike membrane leaks that follow showering.

Substrate damage

Water in timber floors and framing causes rot and termite attack; in fibre cement and plasterboard, swelling and mould; in concrete slabs, corrosion of reinforcement over time.

Mould and condensation

Bathrooms without effective exhaust, or with fans discharging into the roof space, stay humid after showers; mould grows on ceilings, grout and sealant. Fans venting into roof spaces cause condensation and mould there too.

Slips and scalding

Smooth wet tiles cause falls, especially for older people. Hot water without tempering to safe temperatures scalds children and the elderly.

In the bathroom

• Cracked, loose or drummy (hollow-sounding) tiles, especially near the shower and waste.
• Discoloured, missing or cracked grout; mouldy or split silicone at junctions.
• Water ponding on the floor after a shower; water crossing the threshold.
• Exhaust fan weak, noisy or discharging into the ceiling space.
• Mould on ceilings and around the shower.
• Moisture meter readings elevated at the base of walls and around the shower.

Around and below

• Swollen skirtings, door frames and vanity bases near the bathroom door.
• Stained, bubbling or mouldy ceilings in the room or unit below.
• Damp carpet or lifting floor coverings outside the bathroom.
• Rot and termite damage in timber floors below, seen from the sub-floor.

In the records

• Waterproofing certificates and installer details.
• Leak complaints from neighbours below.
• Previous repairs and resealing.
• Building defect claims.

Findings are graded by what they demand: safety (can hurt someone now), failure (failed and damaging the building), condition (distress present and progressing), lifecycle (renewal due on age and exposure), deadline (a regulator or ordinance sets the date), check (investigate before sizing works) and nil (cosmetic or stable).

A building surveyor or wet area specialist leads; a plumber joins for pressure testing; in apartments, access to the unit below is essential.

• Moisture mapping with a meter around the shower, at wall bases, at the threshold and outside the door, and on the ceiling below.
• Thermal imaging to trace wet areas in walls and ceilings.
• Flood test: plug the waste and flood the floor or shower base for a set period, then check below and around for water.
• Spray and use tests of screens and fixtures.
• Dye tests of WC pans and cisterns.
• Pressure test of hot and cold pipework, or a meter test with all outlets closed.
• Invasive inspection: lift a tile at the waste or threshold, or open the ceiling below, to see the membrane and substrate.
• Exhaust check: airflow and where the duct discharges.
• Sub-floor inspection below timber-floored bathrooms for rot and termites.

The report should identify the source of each leak with evidence, the extent of substrate damage, whether the membrane can be repaired or must be replaced, and in strata buildings whether the cause is common property or within the lot.

• Regrout and reseal as maintenance or a short-term measure where the membrane is sound; it does not fix membrane failure.
• Penetrating sealers and surface coatings applied over tiles as temporary measures, with the understanding that they rarely last.
• Strip and re-waterproof: remove tiles and screed, repair the substrate, install a compliant membrane with reinforced junctions, upturns, waste flanges and threshold waterstops, re-screed to falls and retile. This is the only lasting fix for a failed membrane.
• Plumbing repairs of mixers, connections, pan seals and wastes.
• Shower screen repair: new seals, adjustment or replacement.
• Exhaust: replace weak fans with ducted fans discharging outside, with run-on timers or humidity control.
• Substrate repair: replace rotted timber and swollen sheets; treat termite damage.
• Safety: slip-resistant floor tiles and tempering valves on hot water.

Regrouting and resealing are small items but recur. Strip and re-waterproof is priced per bathroom and is a significant project, with temporary loss of the bathroom and making good of adjoining finishes and the ceiling below. Plumbing repairs are itemised. Exhaust upgrades are per fan with ducting. In apartments, consequential damage below often costs as much as the bathroom itself.

Full re-waterproofing is lifecycle or a defect repair; leaks are failures; resealing is repairs and maintenance; in new buildings, claims may fall under statutory warranties.

• Australia. AS 3740 sets waterproofing of domestic wet areas, with a revised edition in 2021 tightening falls, upturns and threshold details; the National Construction Code requires exhaust from bathrooms and laundries to discharge to the outside in newer homes; state home building laws provide statutory warranties against defects (for example in New South Wales), and strata law decides whether the membrane is common property or part of the lot, which varies by plan.
• United Kingdom. BS 5385 covers wall and floor tiling, including wet areas; Approved Document F sets extract ventilation rates; NHBC Standards set warranty requirements for new homes; leasehold terms decide responsibility in flats.
• United States. The International Residential and Plumbing Codes set shower pan and wet area requirements, with membranes commonly to ANSI A118.10 and practice to the TCNA Handbook; exhaust fans must discharge outdoors; condominium declarations set responsibility.

• Waterproofing certificates and installer details.
• Leak complaints from the unit below or neighbours.
• Records of previous repairs, regrouting and resealing.
• Building defect claims and warranty details for newer buildings.
• Strata plan and by-laws defining membrane ownership.
• Plumbing compliance certificates for renovations.

• Moisture or thermal imaging reports from earlier investigations.