In this guide I want to explain why below-ground waterproofing in Bali requires a different approach from above-ground work. Positive-side membranes — applied to the face of the wall that water contacts — work well for roofs and bathrooms. For basement walls and retaining walls, hydrostatic ground pressure from outside is the load, and standard positive-side membranes applied to the interior face simply get pushed off the wall by the pressure they're trying to stop. Negative-side waterproofing — crystalline systems that work within the concrete mass, or drainage board systems that redirect water away from the wall — are the correct tools for below-ground applications. Using a surface membrane on a leaking basement wall is the most expensive mistake I see in Bali below-ground waterproofing.
Below-Ground & Retaining Wall Waterproofing
Crystalline Waterproofing
Crystalline admixtures or surface-applied crystalline slurries penetrate the concrete's capillary network and form insoluble crystals that block water passage permanently. They're particularly suitable for Bali basement and retaining wall applications because they work from inside the concrete mass — hydrostatic pressure from outside doesn't dislodge them. They also self-heal minor cracks as the crystals grow to fill new voids over time.
Drainage Board Systems
For walls with active water seepage, the most practical solution is often to accept that water will continue to penetrate the wall and manage where it goes. Drainage board — dimple-face sheet fixed to the wall face — creates an air gap between the wall and any internal finish. Water that enters through the wall runs down behind the drainage board to a perimeter drain and sump, rather than wetting the internal finish. Practical for occupied basements where structural waterproofing injection is impractical.
Injection Grouting
For active water flow through cracks in basement walls or slabs, polyurethane or acrylic injection resin injected through drilled holes stops the flow at the point of entry. The resin expands on contact with water and fills the crack. Effective for discrete active leaks in otherwise sound concrete — not suitable for porous concrete with distributed seepage.
Retaining Wall Waterproofing
Bali's sloped properties have extensive retaining wall systems. Retaining walls without waterproofing and drainage accumulate hydrostatic pressure behind them — a structural risk, not just a water ingress issue. We install drainage aggregate and drainage pipe systems behind retaining walls, combined with positive-side membrane on the retained face, where access allows.
Below-Ground Waterproofing on Bali's Slopes
Much of Bali is built on slopes — Ubud's valleys, the cliff edges of Uluwatu, the terraced land around Canggu and Berawa. Wherever a structure sits below ground level on one or more sides, it carries hydrostatic pressure from the soil and groundwater behind it. In the wet season that pressure rises sharply, and any wall that was not waterproofed and drained correctly during construction will start to weep, show damp patches, or push white efflorescence salts through to the inside face. Left alone, that constant moisture corrodes reinforcement and, on retaining walls, becomes a structural risk rather than just a cosmetic one.
The fix is rarely a coat of paint or a surface membrane on the inside. Because the water comes from outside, the durable solution works with the concrete mass or manages where the water goes — crystalline waterproofing that becomes part of the slab, drainage boards that channel seepage to a sump, or injection that seals an active crack at source. We choose the combination based on whether the wall has a discrete leak or distributed seepage, and whether the outside face is accessible.
Our Below-Ground Process
Diagnose the water path
We establish whether you have an active crack leak, distributed seepage, or rising damp through the slab — each needs a different treatment.
Stop active flow
Any actively flowing crack is injected with reactive resin to halt the water before other work begins.
Treat the mass
Crystalline slurry is applied to seal the concrete capillaries, self-healing minor future cracks as the crystals grow.
Manage residual water
Where seepage cannot be fully stopped, a drainage board and perimeter drain direct water to a sump so internal finishes stay dry.
FAQ
Why does my basement wall keep getting damp even after waterproofing?
Almost always because a positive-side surface membrane was applied to the interior face. Below ground, water pressure pushes from outside and forces a surface membrane off the wall. These walls need negative-side solutions — crystalline systems or drainage boards — not an inside coat.
What is the white powder on my basement wall?
Efflorescence — salts left behind as water passes through the concrete and evaporates on the surface. It is a reliable sign that moisture is moving through the wall, confirming a below-ground approach is needed.
Can you stop an active leak in a basement wall?
Yes. For water flowing through a crack, injection resin is fed through drilled ports; it expands on contact with water and seals the crack at the point of entry. For widespread seepage we combine crystalline treatment with a drainage board and sump.
Below-Ground Waterproofing Prices in Bali
| Service | Guide Price (IDR) | Notes |
|---|---|---|
| Crystalline treatment (per m²) | 90,000–160,000 | Two-coat system |
| Crack injection (per crack) | 400,000–800,000 | Polyurethane/acrylic resin |
| Drainage board system | by quote | Scope by wall area and access |
See the full pricing page or send photos of the damp wall for a quote.
Related Services
We also handle roof waterproofing, bathroom membranes and pool waterproofing across all our Bali service areas.
Below-Ground Water Ingress?
Describe what you're seeing — active drips, damp patches, white efflorescence deposits — and we'll advise the right diagnosis and treatment approach for Bali's conditions.
WhatsApp for Below-Ground Waterproofing