Fosroc Cemseal
Crystalline capillary waterproofing that grows inside the concrete itself — seal basements, tanks and negative-side leaks without a membrane. Supplied and applied by Space Arc Engineering across Delhi NCR and Pan-India.
What is it?
A powder-form crystalline waterproofing compound blending proprietary cement, quartz and active chemicals that react inside concrete capillaries to form insoluble, water-blocking crystals.
Where is it used?
Basements, underground and overhead water tanks, reservoirs, lift pits, sumps and older structures where only the inner (negative) face can be reached.
Why use it?
It becomes part of the concrete rather than a skin over it — nothing to peel or puncture, it self-seals hairline cracks up to about 0.4 mm, and it resists water pushing from either side.
How is it applied?
Brush-applied as a two-coat slurry at roughly 0.8–1.0 kg/m² per coat on prepared damp concrete, or dosed integrally at 0.8–1.5% by weight of cement during batching.
About Fosroc Cemseal
Fosroc Cemseal is a crystalline capillary waterproofing compound supplied as a dry powder of proprietary cement, quartz and reactive chemicals. Mixed with water and brushed onto concrete, or added straight into the mix at the batching plant, its actives travel through the moisture in the capillary network and lock the pores shut with insoluble crystals. The result is concrete that resists water through its own matrix — there is no membrane to detail, protect or replace. Space Arc Engineering stocks Cemseal for site supply and also executes full application packages with trained crews.
For Indian basements the negative side is usually the only side you get. Once a Noida or Gurugram tower is occupied, nobody is excavating the periphery to redo an external membrane; treatment has to work from inside, against the pressure. That is exactly the situation crystalline chemistry was built for, and it is why consultants increasingly write integral crystalline dosing into new water-retaining structures as well — the waterproofing arrives already inside the concrete.
The technical insight
Concrete is never fully hydrated: free lime and unreacted cement grains sit throughout the capillary system. Cemseal’s active chemicals dissolve into pore moisture and react with these residues to precipitate needle-like insoluble crystals that progressively choke the capillaries and micro-cracks — reported penetration is 50–150 mm from the treated face, far deeper than any coating. Crucially, the chemistry then goes dormant rather than dead. If a new hairline crack (roughly 0.2–0.4 mm) forms years later and water re-enters, the incoming moisture reactivates the residual chemicals and fresh crystals seal the path. Water, the thing that causes the problem, is also the trigger for the cure — which is why damp substrates help this product rather than hurt it.
Where it is used
- Negative-side waterproofing of basement retaining walls and rafts in occupied buildings
- Underground and overhead water tanks, reservoirs and sumps
- Lift pits, tanking sumps and machine foundations sitting below the water table
- Integral waterproofing of new RCC rafts, retaining walls and water-retaining structures via RMC dosing
- Rehabilitation of porous, honeycombed or hairline-cracked concrete after structural repair
- STP and WTP tank structures in continuous wet service
- Tunnels, subways and podium basements where external excavation is impossible
- Back-up waterproofing layer behind or beneath membrane systems on critical structures
Key advantages
- Works from the negative side — treat occupied basements from inside, with no excavation or dewatering of the periphery
- Grows into the concrete matrix, so it cannot debond, blister or puncture the way sheet and liquid membranes can
- Self-seals fresh hairline cracks up to about 0.4 mm whenever moisture re-enters
- Penetrates 50–150 mm deep, protecting well beyond the surface zone that coatings cover
- One material, two methods — brush slurry on existing structures, integral dose in fresh concrete
- Crystals are insoluble and permanent; protection does not wash out or fatigue with wet–dry cycling
- Damp concrete is an advantage, not a hold-up — no waiting for the substrate to dry
- Applied with a stiff brush by regular site crews; no hot works, primers or specialist plant
Limitations & considerations
- Cannot bridge moving cracks, expansion joints or cracks wider than about 0.4 mm — these need waterstops or elastomeric sealants, not crystalline treatment
- Actively flowing leaks must first be arrested with a hydraulic plugging mortar; Cemseal is not an instant water plug
- Needs moisture and about 72 hours of damp curing to develop crystals — early drying out visibly reduces performance
- Crystal growth continues over days to weeks, so hydrotests and tank filling must be scheduled accordingly, not next morning
- Leaves a functional grey cementitious finish — add plaster, screed or tiling where appearance or abrasion resistance matters
- Only for sound cementitious substrates; unsuitable for metal, wood, gypsum or friable, delaminating concrete
Selection & best practice
Preparation decides the outcome. Remove laitance, paint and loose material by wire brushing, grinding or hydro-jetting so the capillaries are open to receive the actives. Arrest any running water first with a hydraulic plugging mortar such as Fosroc Renderoc Plug, anchoring fixtures with Lokset where needed. Pre-wet the concrete to a uniformly damp, saturated-surface-dry state — damp, but with no free-standing water. Mix the powder with clean water to a thick brushable slurry and work the first coat firmly into the surface with a stiff brush; apply the second coat wet-on-wet at around 0.8–1.0 kg/m² per coat. Then protect the work: keep the treated face damp for 72 hours, because the crystals only grow where moisture stays. For the integral route, dose 0.8–1.5% by weight of cement with the dry materials or gauging water at the plant, and always run a trial mix to confirm workability and setting before production pours.
Specifications
| Form | Dry powder — proprietary cement, quartz and active chemicals |
| Integral dosage | 0.8–1.5% by weight of cement |
| Slurry coverage | Approx. 0.8–1.0 kg/m² per coat |
| Number of coats (slurry) | Two, applied wet-on-wet by stiff brush |
| Crack self-sealing capacity | Hairline cracks approx. 0.2–0.4 mm |
| Depth of penetration | 50–150 mm from the treated face |
| Substrate condition | Clean, sound, uniformly damp concrete — no free-standing water |
| Curing requirement | Keep damp for 72 hours after application |
Industry use cases
Residential & Group Housing
Basement seepage in high-water-table pockets of Noida, Gurugram and East Delhi treated entirely from inside — no breaking of driveways, landscaping or neighbouring plots.
Commercial & Institutional
Office tower basements, hospital service floors and lift pits where downtime must stay minimal and membranes cannot be re-laid under live operations.
Water Infrastructure
GSR and ESR storage tanks plus WTP/STP structures — dosed integrally at the batching plant for new tanks, slurry-applied when rehabilitating old ones.
Industrial Plants
Pits, trenches, tank farms and equipment foundations in permanently wet ground, where punctured membranes have repeatedly failed.
Repair & Rehabilitation
Ageing basements and reservoirs where the original waterproofing has failed and replacement from outside is physically or commercially impossible.
Frequently asked questions
Can Cemseal stop basement seepage from inside, without external excavation?
Should I use the slurry or the integral dose?
How much material do I need for a water tank?
The wall is leaking actively — can I brush Cemseal straight on?
How soon after application can we fill or hydrotest the tank?
Is it suitable for drinking-water tanks?
How we position Fosroc Cemseal
Cemseal sits in Fosroc’s crystalline family alongside Brushbond Crystal, the documented crystalline slurry for positive- and negative-side hydrostatic pressure, and Conplast Crystalline and Supercast CWA, the integral crystalline admixtures for ready-mix concrete. On site it pairs naturally with Renderoc Plug and Lokset for arresting live leaks before treatment, while Brushbond and Brushbond RFX cover jobs needing a flexible cementitious coating over movement-prone or exposed surfaces. Where a client’s specification names another house, Space Arc also supplies Dr. Fixit Krystalline as a crystalline equivalent.
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