Sika Sikadur-20 Crack Seal
A solvent-free, semi-elastic epoxy that flows into fine non-structural cracks and cavities and seals them ahead of waterproofing, on dry or damp concrete.
What is it?
A two-component, solvent-free epoxy resin with very low viscosity (~90 mPa·s) and a semi-elastic set, formulated to fill and seal non-structural cracks and cavities in concrete.
Where is it used?
Concrete decks, balconies, roof structures, wet rooms, swimming pools and tile joints, most often as a preparatory seal before membrane or coating waterproofing.
Why use it?
It penetrates hairline gaps by simple gravity feed, bonds strongly to concrete (~2.0 N/mm², concrete failure), stays semi-elastic to absorb minor movement, and works even on damp surfaces free of standing water.
How is it applied?
Groove and clean the crack, mix Part A and Part B 1:1 by volume, and pour the mixed resin into the vee-notched crack until full; add cement or Sika TiloGrout as filler for a flush finish.
About Sika Sikadur-20 Crack Seal
Sikadur-20 Crack Seal is Sika’s low-viscosity answer to the everyday problem every applicator meets before a waterproofing job: fine cracks and open joints that will wick water straight through a fresh membrane if they are left untreated. It is a two-part epoxy resin, mixed one-to-one by volume, that stays thin enough (around 90 mPa·s at 30 degrees C) to run into hairline gaps under nothing more than gravity. Once cured it is semi-elastic rather than rock-hard, so it seals the crack while still tolerating the small thermal and load movements a slab or deck sees in service.
What makes it practical on Indian sites is that it does not demand a bone-dry substrate. The concrete may be dry or damp as long as there is no standing water, which suits wet rooms, terraces, swimming-pool surrounds and roof slabs where getting a surface fully dry is rarely realistic. It is important to be clear about scope, though: this is a non-structural crack sealer, not a structural injection resin. It is the right choice for sealing and leak treatment ahead of waterproofing, and the wrong choice where a crack needs load-bearing structural bonding.
The technical insight
The product works on a simple principle: capillary action plus a controlled cure window. Because the mixed resin sits at roughly 90 mPa·s, close to a light oil, it is drawn into cracks far finer than a trowel-grade mortar could ever reach, wetting both crack faces completely. The pot life of over 20 minutes at 30 degrees C keeps it fluid long enough to migrate and fill before it starts to gel. As it cures it develops a tenacious bond to concrete, tested at about 2.0 N/mm² tensile adhesion to EN 1542 with failure occurring in the concrete rather than at the glue line, meaning the epoxy is stronger than the substrate it seals. The semi-elastic (rather than brittle) cured film is deliberate: a fully rigid epoxy in a moving crack simply re-cracks, whereas a semi-elastic seal flexes with minor movement and stays watertight. Being solvent-free, it neither shrinks back out of the crack nor off-gasses as it hardens.
Where it is used
- Sealing non-structural cracks and cavities in concrete slabs, decks and balconies
- Preparatory crack sealing before applying a waterproofing membrane or coating
- Leak treatment of floor tile joints in wet rooms and bathrooms
- Sealing cracks and cavities in swimming pools and water-adjacent structures
- Concrete roof-structure crack sealing ahead of terrace waterproofing
- Gravity filling of vee-notched hairline cracks in floors
- Making good open joints and shrinkage cracks that would otherwise track water
- Flush repair of cracks using the resin blended with cement or Sika TiloGrout as a filler
Key advantages
- Very low viscosity (~90 mPa·s) so it self-penetrates fine cracks by gravity, no injection rig needed
- Works on dry or damp concrete, only standing water must be removed
- Semi-elastic cure accommodates minor movement instead of re-cracking like a rigid epoxy
- Strong bond to concrete, ~2.0 N/mm² with concrete failure to EN 1542
- Solvent-free with no shrinkage, so it stays in the crack it fills
- Simple 1:1 by-volume mixing that is hard to get wrong on site
- Comfortable pot life of over 20 minutes at 30 degrees C for unhurried placement
- Can be extended with cement or Sika TiloGrout to finish flush with the surface
Limitations & considerations
- Non-structural only, not a substitute for a load-bearing structural injection resin
- Maximum crack width is 10 mm, wider gaps need a different repair system
- Concrete must be at least 28 days old before application
- Will not seal against standing water, cracks must be grooved and cleaned dry of pooled water first
- Supplied only in a small 140 mL (70 + 70 mL) set, which is uneconomical for large crack areas
- Pot life and flow shorten as temperature rises, so mix small batches in hot weather
Selection & best practice
Start by confirming the concrete is at least 28 days old, then groove out each crack or tile joint to a clean vee-notch and remove all dust, laitance and pooled water; the surface may stay damp but never wet. Mix only what you can place within the pot life: shake each component, combine Part A and Part B 1:1 by volume in a clean bottle and invert it 15 to 20 times until uniform, rather than whipping in air. Pour the mixed resin straight into the notched crack and let gravity carry it down until the crack is full, topping up as it settles. For a flush finish, blend the mixed resin with cement (1 part resin to 2 to 3 parts cement) on concrete, or with Sika TiloGrout in the same ratio on tile joints, and strike off with a putty blade. In hot conditions keep batches small, and protect fresh work from direct sun and rain until it has gelled.
Specifications
| Chemical base | Solvent-free, 2-component epoxy resin (low viscosity, semi-elastic) |
| Colour | Yellowish |
| Mixing ratio | Part A : Part B = 1 : 1 by volume |
| Density (mixed) | ~1.05 kg/L (EN ISO 2811-1) |
| Viscosity | ~90 mPa·s (Brookfield 2/30, +30 °C) |
| Pot life | >20 min at +30 °C |
| Tensile adhesion strength | ~2.0 N/mm² (concrete failure, EN 1542) |
| Flexural behaviour | Elastic, 28 days cured at +30 °C (ASTM D790) |
| Maximum crack width | 10 mm |
| Packaging | 140 mL set (Part A 70 mL + Part B 70 mL) |
| Shelf life / storage | 12 months; store +10 °C to +35 °C, away from sunlight and frost |
Industry use cases
Waterproofing contractors
Seal hairline cracks and open joints on terraces and roof slabs before laying a membrane, so water cannot track under the fresh waterproofing.
Wet-area and bathroom renovation
Treat leaking floor tile joints in wet rooms by grooving and filling with the resin blended with Sika TiloGrout for a flush, watertight joint.
Swimming pool builders
Fill and seal non-structural cracks and cavities in pool shells and surrounds where the substrate is damp but movement is minimal.
Facility and building maintenance
Quick, gravity-fed sealing of shrinkage and settlement cracks in balconies, decks and floors as part of routine leak repair.
General concrete repair crews
Keep a small-batch, easy 1:1 epoxy on hand for spot-sealing fine cracks ahead of coatings without needing injection equipment.
Frequently asked questions
Can Sikadur-20 Crack Seal be used to repair structural cracks?
Does the concrete surface have to be completely dry?
What is the maximum crack width it can handle?
How do I get a flush, finished surface after filling the crack?
What is the pot life and how much should I mix at once?
How is it packaged and how far will it go?
How we position Sika Sikadur-20 Crack Seal
Sikadur-20 Crack Seal sits at the light-duty, pre-waterproofing end of Sika’s crack-repair range: it is the product to reach for when you need to seal fine non-structural cracks and leaking joints, not to structurally bond them. Where a crack is structural and needs load transfer, step up to a higher-strength injection or bonding epoxy from the Sikadur family rather than this sealer. It also pairs naturally with the waterproofing it precedes, so Space Arc customers commonly buy it alongside a Sika membrane or cementitious coating for the same job. Across our other brands, contractors who prefer Fosroc for repair work often specify Nitofill LV or a Renderoc/Nitomortar repair mortar for the same crack-and-patch scope, and Dr. Fixit or Asian Paints SmartCare systems for the waterproofing layer that follows.
Fosroc Nitofill LV — Choose Nitofill LV when the crack is structural and needs a stronger, injectable low-viscosity epoxy to restore load transfer, rather than a non-structural gravity seal.
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