A damp or leaking basement wastes the most valuable space in the building and threatens the structure above it. Goliath Coatings specialises in basement leak repair and waterproofing across Auckland — diagnosing where water is getting in and tanking the space so it stays permanently dry and usable.

Basement leak repair starts with the source

Successful basement leak repair depends on finding how water is entering — through the wall-floor junction, a construction joint, a crack under pressure, or rising damp through the slab. We assess the water table, the ingress points and the existing structure before we use anything, because sealing the wrong surface simply moves the problem somewhere else.

Signs your basement needs waterproofing

Most Auckland basements give plenty of warning before a full flood: a musty, damp smell, white salt deposits (efflorescence) on the concrete, tide marks or staining low on the walls, paint that bubbles or peels, pooling water after heavy rain, or persistent condensation and mould. Any of these means water is already moving through the structure — the sooner it is tanked, the less remedial work the finishes need.

The waterproofing systems we use

We tank basements with the system the situation demands. For negative-side (internal) pressure we bond cementitious tanking slurries to the concrete — products such as Mapei Mapelastic Foundation, which is rated for both positive and negative hydrostatic pressure. For positive-side and blind-side protection we use self-adhesive and sheet membranes such as Bituthene 3000 and Preprufe, Sika SikaProof A and Sika BlackSeal, or peel-and-stick systems like Sealco BondSEAL. On existing or already-leaking slabs we use penetrating crystalline waterproofing — Xypex and Markham Aquron — which seals the concrete matrix itself. We add liquid-applied membranes for seamless coverage, crack injection to seal active leaks under pressure, and cavity drainage membranes that manage water to a sump where blocking it outright is not practical. Often the right answer is a combination, detailed carefully at every joint.

Waterproofing a basement from the outside

Where we can get access, the most durable fix is to treat the basement from the positive (water) side. We excavate a trench down to the foundation footing, clean and prepare the exposed wall, and apply a torch-on membrane — systems such as Nuralite Nuraply 3PM, Sealco FlameSEAL or Allco Casali, or self-adhesive Bituthene 3000 — so water is stopped at the outer face before it ever reaches the structure. We then add a protection board and a drainage layer that carries ground water down to a subsoil drain, and backfill. External tanking like this stops the leak at its source and is the preferred approach whenever the outside of the wall can be reached.

Turning a wet basement into usable space

A properly tanked basement becomes dry, healthy storage, a workshop or a living area instead of a damp liability. We treat the cause, finish the surfaces to take paint or lining, and stand behind the work — so you reclaim the square metres rather than fighting the same leak every winter.

Why choose Goliath Coatings

Basement tanking and below-ground waterproofing are a core specialty. We own our prep and application equipment, specify premium systems matched to the job, and back every project with genuine 5-star Auckland reviews. You get a free on-site assessment and a one-business-day response.

Basement leak repair FAQs

Q: Why is my basement leaking?

A: Usually water under pressure finding the weakest path — a joint, a crack or the wall-floor junction. We locate the actual entry point before quoting a fix.

Q: Can a basement be waterproofed from the inside?

A: Yes — internal negative-side tanking with cementitious slurries such as Mapelastic Foundation, plus cavity drainage, lets us keep a basement dry without excavating the outside face.

Q: Can you waterproof a basement from the outside?

A: Yes — where there is access we dig down to the footing and apply an external torch-on or self-adhesive membrane (such as Nuraply 3PM or Bituthene 3000) plus a drainage layer, stopping water at the outer face. It is the most permanent fix when the outside wall can be excavated.

Q: What products do you use to waterproof a basement?

A: It depends on the cause and whether we can work from outside or in — typically Mapelastic Foundation, SikaProof or Sika BlackSeal, Bituthene 3000 and Preprufe, or crystalline systems like Xypex and Aquron for existing slabs. We use the system to the situation, not the other way around.