On a lot of Laguna and Cavite sites you hit water at two metres. That single fact decides the below-grade specification, and it is decided before the mat slab is poured — not after the basement starts weeping.
What each system actually does
Bentonite geotextile is a mechanical barrier. Sodium bentonite between two layers of geotextile swells on contact with water and seals against the concrete face, including against minor honeycombing and tie-rod holes. It is laid against blinding before the raft, or fastened to the wall face before backfill, with 100 mm laps.
Crystalline capillary treatment is chemical. A reactive slurry is brushed onto a saturated surface-dry substrate and grows crystals into the pore structure of the concrete itself. It keeps reacting for the life of the structure, which is why it re-seals hairline cracks that open after handover.
Choosing between them
- Blind-side application, where you cannot get to the positive face after the pour — bentonite. Crystalline needs access to a surface you can prepare.
- Permanent hydrostatic head against a wall you can reach from outside before backfill — either works; bentonite is faster over large areas.
- Water tanks and STPs, where the water is on the inside and potable contact matters — crystalline, with a potable-grade topcoat where specified.
- Existing structure already leaking, no excavation budget — crystalline, applied negative-side, with injection at active cracks.
- Movement expected at a construction joint — neither on its own. That is a waterstop detail.
Where both belong together
On a deep basement with a high table we will often specify bentonite to the raft and walls, a self-swelling waterstop at every cold joint and penetration, and crystalline slurry to the internal face of lift pits and tanks. That is not belt-and-braces — the three are solving different failure modes.
What to put in the spec section
- Substrate
- Structural and blinding concrete, CHB, shotcrete
- Preparation
- Sound, free of laitance and standing water; SSD for crystalline
- Laps
- 100 mm minimum, fastened per manufacturer
- Joints
- Self-swelling waterstop at all cold joints and penetrations
- Protection
- Protection board before backfill — not optional
- Warranty
- 5–10 years, confirmed per system at quotation
If you want this written against your drawings, send the basement sections and we will mark up the system and the details.
Written by the INTRIC technical desk. If this raised a question about your substrate, ask it — send the detail and you get an answer, not a sales call.