Basement Waterproofing near you

The NCC's performance requirements for Class 1 houses set the benchmark. Surface water from a storm with a five per cent annual exceedance probability must be disposed of in a way that avoids the likelihood of damage or nuisance to any other property, and water from a one per cent annual exceedance probability storm must not enter the building. Moisture from the ground must be prevented from causing unhealthy or dangerous conditions, loss of amenity, or undue dampness and deterioration of building elements. If your lower level is wet, one of those is not being met.

Expect the first visit to be spent outside rather than inside. A contractor should walk the fall of the land around the whole building, check where every downpipe discharges and whether it is connected to stormwater, look for a bridged damp-proof course, check subfloor vents, and ask what changed recently, because a new deck, a new driveway, a raised garden or a neighbour's regrading is very often the trigger.

Then the timing question: does the water appear during rain, hours afterwards, or constantly? Water that arrives during heavy rain and stops points to surface water and drainage. A wall that is permanently damp low down, with salt bloom on the render, points at rising damp or a bridged damp-proof course. Water that appears when the shower upstairs is used is not a below-ground problem at all.

Only then does the fix get chosen, and it is usually the cheapest layer that works: regrade and redirect surface water first, correct the stormwater, clear the subfloor, then drainage behind the wall, and only then excavation and tanking. Get the diagnosis in writing, with the reasoning, so you can compare quotes that propose different work rather than the same work at different numbers.

For internal wet areas, the ABCB Housing Provisions Part 10.2 sets out what must be waterproof or water resistant, and AS 3740 is the standard for waterproofing domestic wet areas and can be used as the construction solution. The detail is specific: shower walls must be waterproof to not less than 1800 millimetres above the floor substrate, wall junctions and joints within the shower area must be waterproof not less than 40 millimetres either side, and the floor of a wet area containing a vessel must be graded to a floor waste so water can drain. AS 3740 was revised in 2021 and that edition is the one referenced in NCC 2022.

Under a slab, the damp-proofing membrane is a defined product, not builder's plastic: polyethylene film of 0.2 millimetres nominal thickness with the required impact resistance, branded continuously as an AS 2870 concrete underlay, lapped not less than 200 millimetres at all joints and sealed around service penetrations.

For subfloors, the Housing Provisions require cross ventilation of the space between the underside of the floor and the ground, and where the ground or subfloor space is excessively damp or subject to frequent flooding the required ventilation must be increased by half, or the ground within the subfloor sealed with an impervious membrane. Above ground, masonry weatherproofing and damp-proof courses follow AS 3700 or the AS 4773 series.

Retaining walls and excavation are where approvals bite. In New South Wales, some retaining walls are exempt development under the State Environmental Planning Policy for exempt and complying development, with criteria covering height and distance from the boundary, and anything that misses those criteria needs a complying development certificate or development consent. In Victoria, building work generally needs a building permit unless the regulations exempt it, and excavating for a retaining wall below a set height is among the exemptions. The thresholds differ in every state, they change, and they interact with your specific block, so confirm with your council or a registered building surveyor for your address rather than with a rule of thumb.

Licensing is separate again, and also state by state: most jurisdictions require a licensed or registered contractor above a set contract value, and plumbing and drainage work is licensed in its own right, in Queensland at any value at all. Waterproofing is a defined class of work in some states. Ask which licence class covers the specific work being proposed, and check the number on your regulator's public register.

LokalMatch helps with the sourcing, not the deciding. You post one description of the problem, with where the water appears, when it appears and what the lower level is used for, and matched waterproofing and drainage contractors contact you. Those businesses pay for the requests. LokalMatch performs none of the work, sets no prices and does not vet, rank or endorse any contractor, so verifying licences, insurance and approvals stays with you.

Waterproofing is one of the most commonly rectified defects in Australian housing, so the statutory schemes matter here more than almost anywhere. In New South Wales, home building compensation cover must be taken out by the principal contractor before any work starts or any money changes hands on contracts above the scheme threshold, and it responds to major defects for six years and other losses for two years from completion. Queensland's Home Warranty Scheme covers insurable residential building work above its threshold, with the contractor paying the premium. Victoria requires domestic building insurance at or above its threshold, with the certificate of currency provided before any money is taken. South Australia requires building indemnity insurance for approval-requiring work above its threshold.

On top of that, the Australian Consumer Law guarantees enforced by the ACCC apply: the service must be carried out with acceptable care and skill and be fit for the purpose you made known. Telling the contractor in writing that the purpose is to keep the lower level dry in heavy rain is worth doing, because it makes the purpose explicit.

Ask what the workmanship warranty covers and how a return visit is triggered, and keep the diagnosis, the scope, the product data sheets and the certificates together. If the wall is wet again two winters later, that file is what turns an argument into a claim.