Sikalastic Moisture Seal 20L – Two Part Epoxy Waterproofing Primer

Stop moisture in its tracks before it compromises your floor coating. Sikalastic Moisture Seal is a high-performance, two-component water-based epoxy that chemically cures to form a robust vapour barrier — resistant to hydrostatic pressure and capable of preventing rising damp. Whether you're priming damp concrete in a basement, waterproofing a green screed, or preparing a surface for a liquid-applied membrane, this is the product that gets the job done right the first time.

Available exclusively at Epoxy Warehouse — Australia's trusted supplier of professional-grade floor coating systems.

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Key Benefits

• ✅ Excellent adhesion to damp substrates — apply directly over damp or green concrete and screeds
• ✅ Dual-function: primer + moisture barrier — eliminates the need for two separate products
• ✅ Hydrostatic pressure resistant — ideal for below-grade and negative pressure applications
• ✅ Low VOC formula — safe for use in confined and poorly ventilated spaces
• ✅ Non-flammable — reduced site risk during application
• ✅ Simple 1:1 mix ratio — no guesswork, less waste
• ✅ Water clean-up — easy tool and equipment maintenance on site

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Recommended Applications

• Waterproofing and priming of damp or green concrete slabs
• Waterproofing and priming of damp or green cement screeds
• Rendered brickwork, rendered blockwork, and fibrous cement sheeting
• Negative pressure waterproofing applications
• Moisture vapour barrier coating for green screeds prior to floor coating installation
• Primer coat prior to application of liquid-applied waterproofing membranes

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Technical Data

Mix Ratio	1:1 by volume (Part A : Part B)
Coverage – Moisture Barrier	Minimum 2 coats at 3 m² per litre per coat
Coverage – Primer	1 coat at 10 m² per litre per coat
Pot Life @ 25°C	90 minutes
Pot Life @ 35°C	45 minutes
Overcoating Window	Minimum 6 hours, maximum 48 hours
Full Cure	7 days
Application Temperature	10°C – 35°C (substrate)
Pack Size	20 Litres

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Application Instructions

Surface Preparation

All surfaces must be firm, clean, structurally sound, and free from grease, oil, wax, curing compounds, dust, laitance, and loose material. Remove all projections and rough spots to achieve a level, continuous surface. Previously coated or treated substrates must be mechanically prepared to expose a clean, contaminant-free surface.

• Concrete: Allow a minimum of 72 hours cure time before application. Repair surface imperfections with a suitable Sika® MonoTop repair mortar.
• Cement render / sand screeds: Allow a minimum of 24 hours cure time before application.
• Sheeting: Fix in accordance with the manufacturer's installation directions.

Mixing

Thoroughly stir Part A and Part B separately before combining. Measure equal volumes of each part and pour into a clean container. Using a mechanical mixer, blend until a homogeneous liquid is achieved — take care to avoid air entrapment. Do not mix more product than can be used within 90 minutes at 25°C.

Application

Apply by brush, roller, or airless spray. For moisture barrier applications, apply a minimum of 2 coats at 3 m²/L per coat. For use as a primer, apply 1 coat at 10 m²/L. Allow a minimum of 6 hours and a maximum of 48 hours between coats and prior to overcoating with a waterproofing membrane. If the 48-hour window is exceeded, apply an additional coat of Sikalastic® Moisture Seal to reactivate the surface and extend the overcoating interval.

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Limitations

• Do not apply over existing protective coatings
• Do not apply in rain or if rain is imminent
• Not recommended for metal surfaces (risk of corrosion)
• Must cure for a minimum of 72 hours before full immersion or water testing
• Not suitable as a trafficable, UV-stable, or exposed coating
• Not recommended as an efflorescence barrier for sand cement screeds or render
• Not suitable to be tiled over
• Do not apply below 10°C or above 35°C substrate temperature
• Discard any material that has exceeded pot life
• Ensure adequate ventilation in enclosed areas during application and cure

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Pair It With the Right Waterproofing System

Sikalastic Moisture Seal is designed to be used as part of a complete Sika waterproofing system. Once your primer coat has cured, top it with one of these compatible membranes available at Epoxy Warehouse:

• Sikalastic 487 Elastomeric PU Waterproofing Membrane – 15L Grey — flexible polyurethane membrane for demanding waterproofing applications
  

Download Datasheets

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Frequently Asked Questions

Can Sikalastic Moisture Seal be applied to wet or damp concrete?

Yes — this is one of its standout features. Sikalastic® Moisture Seal is specifically formulated for application over damp and green concrete and screeds, making it ideal for situations where full drying is not possible before waterproofing or coating work must proceed.

How many coats do I need for a moisture barrier?

A minimum of 2 coats is required when using Sikalastic® Moisture Seal as a moisture vapour barrier, applied at a rate of 3 m² per litre per coat. When used solely as a primer prior to a waterproofing membrane, 1 coat at 10 m²/L is sufficient.

How long do I need to wait between coats?

Allow a minimum of 6 hours and a maximum of 48 hours between coats. If the 48-hour window is exceeded, apply an additional coat of Sikalastic® Moisture Seal to reactivate the surface before proceeding.

Is Sikalastic® Moisture Seal safe to use indoors?

Yes. It is a low VOC, water-based, non-flammable product — making it well-suited for use in confined spaces and indoor environments. Ensure adequate ventilation is provided during application and curing.

Can I tile over Sikalastic® Moisture Seal?

No. Sikalastic® Moisture Seal is not suitable to be tiled over. It is designed as a primer and vapour barrier to be used in conjunction with compatible Sika® liquid-applied waterproofing membranes. Contact Sika Technical to confirm membrane compatibility before use.

What is the pot life of Sikalastic® Moisture Seal?

At 25°C, the pot life is 90 minutes. At 35°C, this reduces to 45 minutes. Only mix as much product as you can apply within the pot life window — discard any material that has exceeded working time.

Is Sikalastic® Moisture Seal suitable for negative pressure waterproofing?

Yes. It is specifically listed for negative pressure waterproofing applications, making it suitable for below-grade walls and structures where water pressure acts from the outside in.

Where can I buy Sikalastic® Moisture Seal in Australia?

Sikalastic® Moisture Seal 20L is available online at Epoxy Warehouse with Australia-wide shipping. Add to cart above or contact our team for bulk pricing and trade enquiries.

Colour accuracy disclaimer: We have taken care to display the most accurate visuals of our products. However, we are not responsible for the colour accuracy of the device you are viewing our swatches on. These variations arise due to different computer monitors and devices (make, model and technology, as well as resolution, contrast and brightness control settings) in much the same way a scan will differ from an original image and a colour photocopy. Furthermore, coatings can exhibit variation in perceived colour depending on gloss level and application method. If you require a very specific colour match, please make your selection via actual swatches and colour boards available at our showroom.

Product Disclaimer: Ensure you read all product, technical and safety data sheets prior to application as liability falls on the applicator. All products must be applied in accordance with manufacturer’s recommended method.