Waterproofing is one of the most important steps in protecting any structure from water damage, leaks, and deterioration — and liquid waterproofing membranes are leading the way in modern construction and renovation. A liquid membrane creates a seamless, flexible, and durable barrier that prevents moisture penetration, making it ideal for waterproofing concrete, balconies, showers, bathrooms, decks, and façades, as well as waterproofing under tiles and over tiles.

Below is a deep dive into liquid waterproofing membranes, including how they work, how to apply them, why they’re the best option, and how SEMCO Liquid Membrane™ stands apart.

If you’re looking for a versatile, high-performance liquid waterproofing membrane that simplifies specification, covers a wide variety of substrates, allows for DIY or trade application, and meets Australian standards — SEMCO Liquid Membrane™ is your solution.

A liquid waterproofing membrane is a fluid coating that cures in situ to form a continuous, seamless, elastic membrane. Once cured, it forms a barrier to moisture ingress, prevents water damage, and often bridges cracks or gaps in substrates.

With the SEMCO Liquid Membrane™, you have a product that:

• can be applied beneath new finishes or on top of existing surfaces
• is suitable for numerous substrates (wood, tiles, brick, concrete, etc)
• provides elastomeric performance (not just a rigid coating) with high elongation
• combines waterproofing and anti-fracture protection in one formula

In simple terms, it’s like painting on a flexible “skin” that protects your surface from water, leaks, cracks, and moisture-related damage.

Versatility across substrates

Liquid products are suitable for internal and external use over a wide range of substrates — SEMCO Liquid Membrane™ can be applied on wood, tiles, brick, concrete, metal and 10+ more materials. This means one product can replace multiple traditional systems, simplifying specification and inventory.

Seamless & continuous barrier

Because it’s liquid-applied, it forms a continuous film. This helps avoid issues of sheet membranes (seams, laps, adhesives) and provides excellent coverage even on irregular or complex substrates.

Crack bridging + elongation

Choose a formula that offers more than one form of protection. SEMCO Liquid Membrane™ has up to 1300% elongation (i.e., can stretch up to 13 × its original length) to accommodate natural substrate movement, cracks and structural expansion/contraction — a suitable anti-fracture measure for your surfaces.

This is especially important in areas prone to micro-movement, such as timber substrates, balconies, substrates over older buildings, or where substrate movement is likely.

Speed and cost-efficiency

For both DIY users and trade professionals, liquid systems are easy and fast to apply. Quick-drying formulas take just a day to install with a roller or brush. Our system is compatible with spray guns, too.

Suitable for many situations

You can use it for:

• Waterproofing balconies
• Waterproofing showers
• Waterproofing under tiles and over tiles
• On wood, MDF (if prepared properly)
• On existing concrete, new concrete
• Metal, aluminium, asphalt in some cases.

Certifications & standards compliance

SEMCO Liquid Membrane™ is certified as a Class III Waterproofing Membrane, and meets Australian Standards: internal (AS 4858) & external (AS 4654.1-2012) applications. Having that certification provides assurance to specifiers, contractors and DIY end-users.

Here are some of the standout specifications for our product:

• Water-based, single-component (no mixing required) membrane.
• Coverage: Each litre provides ~2-3 m² at 2 coats (≈1 mm total thickness) depending on substrate porosity.
• Cost-efficiency when compared to some traditional membranes.
• Elongation: Up to ~1300% (i.e., stretch up to 13× original length) which is very high.
• Colour options: Available in semi‐clear, white, rockslide grey, black pearl, cove blue, sandy beige, brown slate, and classic SEMCO orange.
• Sizes: 500 mL, 1 L, 4 L, 10 L
• Warranty: 5-year standard limited warranty; 10 years for non-traffic surfaces.
• Trafficable surfaces: Can be used as a finished trafficable coat, when sealed with SEMCO Titan Shield Gloss sealer

Ready to buy SEMCO Liquid Membrane™?

Different substrates impose different surface preparation, constraints, and application details. Here is a breakdown based on our product guidelines.

Waterproofing Concrete (New or Existing)

• Preparation: Sanding (e.g., 60-grit) to remove laitance, roughen smooth surfaces. Cleaners (Nu-Lift, Stone Soap) for deposits/efflorescence.
• Application: Use 12 mm nap roller (or brush/spray) to apply first coat (~0.75 mm). Once dry to touch (1-2 hrs typical at 21 °C), apply second coat in alternate direction. Total required thickness ≈1 mm for non-submerged applications
• Curing time: Typically initial cure 6-7 days, depending on temperature/humidity.
• Notes: Avoid applying in direct sunlight or in conditions > 30 °C as drying too fast can hinder bonding. Substrate must be dry (max 3% residual moisture). For submerged applications (e.g., pools), 3 coats @1mm each are required.

Waterproofing Tiles (Under/Over Tiles)

• Favourite scenario: You can apply SEMCO Liquid Membrane™ as primary waterproofing and then tile over it with your thin-set/mortar.
• Preparation: Clean thoroughly (Power Cleaner + Nu-Lift) using “Prep C” method for tiles. Ensure surface is free of debris, grease, residues. Mask off areas not being waterproofed.
• Application: Same methodology—first coat, second coat at ~0.75 mm each. Inspect for pinholes/voids.
• Important to note: For tiles over the membrane, ensure compatibility of thin-set, tile adhesive and check manufacturer’s tile adhesive instructions for membranes.

Waterproofing Wood Surfaces

• Preparation: Sand with 60 grit sandpaper; remove loose coatings and ensure surface is dry. Don’t pressure wash wood as wood absorbs water.
• Application: Same as above. Total ≈1 mm thickness. Curing etc as above.
• Use-case: Decking under tiles or wood substrates where a waterproof barrier is required.

Waterproofing Metal / Aluminium

• Preparation: Surface must be sanded, cleaned using Power Cleaner & Nu-Lift (Prep C). Rust must first be primed; avoid muriatic acid.
• Application: Same 0.75 mm per coat approach. For non-porous surfaces like metal/fibreglass apply thin coats to allow curing.

Waterproofing Asphalt

• Preparation: Remove debris, clean using Stone Soap & Power Cleaner (Prep B). Slightly dampen surface before cleaning to reduce penetration issues.
• Application: As above. Total ≈1mm for non-submerged surfaces.

Waterproofing WR Board & Brick

• WR Board: Clean with Stone Soap (Prep A). For joints between boards use fabric reinforcement to bridge joints before coating.
• Brick: Clean with Stone Soap & Nu-Lift (Prep D). Then apply as above.

Performance Strengths of SEMCO Liquid Membrane™

• A high elongation (up to 1300%) means excellent crack-bridging capability — key for substrates with movement.
• Seamless barrier = fewer weak-points than sheet membranes or patch systems.
• Versatility across many surface types (wood, tile, brick, concrete).
• Licensed certification (AS 4858 / AS 4654.1-2012) giving confidence in compliance.
• Water-based, low-VOC (<14 g/L) product for more environmentally-friendly application.

Limitations & Risks

• Though versatile, because it’s liquid-applied, performance depends heavily on substrate preparation, correct application thickness, and curing conditions. If any of these are neglected, performance may suffer.
• It is not recommended for potable (drinking) water applications.
• Slip resistance is dependent on the substrate and finishing system; the membrane by itself does not have a slip-resistance rating. If the membrane is left as a finish, you may need to add anti-slip between coats prior to sealing.
• If applied over wet substrates, or substrates with too high residual moisture (>3 %), the film can stay tacky, fail to cure properly or delaminate.
• Rapid drying (due to high temperatures, direct sunlight) may impair bonding — best applied in more moderate conditions.

Best Practice Tips

• Always test substrate moisture content (especially existing concrete, plaster, wood).
• Ensure good ventilation and environmental conditions (moderate temperature, avoid direct sun).
• Use fabric reinforcement around joints, cracks, transitions.
• Always check compatibility of tile adhesives, sealers, etc above the membrane.
• Avoid applying when substrate temperature is above 30 °C or in direct strong sunlight which may cause too-fast drying.
• If using as trafficable finish, include proper sealer (eg Titan Shield Gloss) and consider anti-slip additions.
• Keep substrate flat, clean, free from contaminants (oil, grease, old coatings) — cleaning and preparation are critical.
• Keep thickness consistent; aim for ~1 mm total for most applications unless specified otherwise.

Shop SEMCO Liquid Membrane™ and get 10% off your first order!

Exterior environments are brutal on building materials: full sun, UV exposure, rain, freeze–thaw (in cooler regions), thermal cycling, and constant movement from substrates that expand and contract. A high-quality liquid waterproofing membrane shines here because it creates a seamless, elastomeric skin that flexes with the substrate while resisting weathering and UV degradation.

Are Liquid Membranes Suitable Outdoors?

Modern liquid waterproofing membranes are not only suitable for outdoor use, they’re engineered for it. Traditional waterproofing systems like sheet membranes or bituminous coatings often struggle with exposure to UV radiation, temperature swings, and substrate movement. In contrast, high-performance liquid membranes such as SEMCO Liquid Membrane™ are formulated to withstand Australia’s harsh exterior conditions.

• Seamless protection: No laps or welds to fail around complex shapes (parapets, balustrade posts, drains, thresholds).
• Crack-bridging: Elastomeric elongation helps span hairline cracks and accommodate movement from heat/cold cycles.
• Detailing made easy: Brush, roller, or spray lets you coat the entire surface area.
• UV resistance: Exterior-rated liquid membranes (like SEMCO Liquid Membrane™) are UV-resistant, so they won’t chalk or become brittle when exposed to sunlight. This preserves flexibility and waterproofing performance over time.

Typical Exterior Applications

• Balconies & terraces (under tiles or exposed finish)
• Roofing & podiums (beneath pavers on pedestals or as a sealed finish)
• Planter boxes & parapets (vertical + horizontal transitions)
• Façade details, sills, and thresholds
• Masonry walls & retaining structures (positive-side waterproofing)
• Metal substrates (flashing, stair pans, sheet metal repairs) after proper prep

UV Proofing & Weathering

Exterior-rated liquid membranes like SEMCO Liquid Membrane™ incorporate UV-resistant polymers and additives so the cured film retains elasticity and cohesion under prolonged sun exposure. Practically, this means:

• Less chalking and embrittlement over time.
• Stable elongation and adhesion, preserving crack-bridging capability.
• Colour options that hold up in the sun when the membrane is used as a finish.

Roofs and balconies can swing 40 °C+ across a day. Choosing a membrane with high elongation and strong adhesion to handle expansion/contraction at control/expansion joints (use fabric reinforcement), changes in plane (wall-to-floor upstands) and penetrations (balustrade bases, pipe boots, outlets).

Maintenance & Longevity (Outdoor)

• Movement accommodation: Use reinforcement fabric at all joints, corners, penetrations, and substrate changes.
• Drainage plan: Minimum falls, primary + overflow outlets, and accessible maintenance points.
• Inspect annually (and after extreme weather) for nicks, ponding, or detailing damage.
• Touch-up localised damage quickly — one of the advantages of liquid membranes is easy repairability.

When selecting a waterproofing membrane, consider the following criteria — and see how SEMCO Liquid Membrane™ stacks up.

Criteria

• Substrate type (concrete, wood, tile, metal, etc)
• Movement/crack risk of substrate
• Internal vs external application
• Waterproofing top coat requirements
• Compatibility with tile adhesive/finish
• Film thickness and application ease
• Environmental exposure (UV, weather, temperatures)
• Certification to relevant standards (AS, AWA, etc)
• Cost per m² and ease of application (DIY vs trade)

How SEMCO Liquid Membrane™ compares

• Substrate versatility: Suitable for 15+ substrates (wood, tile, concrete, metal) — very broad.
• High elongation: Excellent crack bridging potential.
• Ease of application: Water-based, single component, can use roller/spray/brush; DIY friendly.
• Waterproof Top Coat/Trafficable finish: Can be used as a waterproof top coat and if required can be sealed for trafficable surfaces
• Certification: Complies with AS 4858 and AS 4654.1-2012 as Class III.
• Cost-effectiveness: At ~2-3 m² per litre for 2 coats; cost per m² is favourable.
• Application instructions: Very clear on prep, coverage, curing times.
• Limitations: Not self-levelling; not yet recommended for potable water; slip resistance depends on finishing system.

So for a wide-range of applications — balconies, showers, tiles over existing surfaces, wood substrates, etc — SEMCO Liquid Membrane™ is Australia’s top choice. Buy it now.

Here are some typical scenarios where you might use SEMCO Liquid Membrane™:

Waterproofing Showers

Wet-area waterproofing under tiles is critical to prevent leaks, mould, substrate damage. Applying the liquid membrane under the tile finish ensures a flexible, seamless barrier across the entire surface, including corners, joints and penetrations.

Waterproofing Balconies & Rooftops

Balconies, terraces and rooftops are exposed to weather, structural movement, tiles, drains, and risk of water ingress into the structure below. Using a liquid membrane that bridges cracks and adheres to a variety of substrates (timber joists, tile backer boards, concrete slab) ensures a robust system.

Waterproofing Under Tiles & Over Tiles

• Under tiles: Apply membrane first, then tile over.
• Over tiles (existing tiles needing waterproofing): The product supports application over existing tiles (after correct preparation) to waterproof an existing floor without removal.

Both are significant for renovation use-cases (saving the cost and mess of tile removal).

Waterproofing Wood & MDF

Wood substrates (decking, subfloors, timber framed balconies) pose challenges: movement, water absorption, rot risk. A flexible liquid membrane helps manage movement, provide a barrier against wetting, and protect the structure.

Waterproofing Concrete & Brick

Concrete and brick structures (planter boxes, walls, pavements) are prone to moisture ingress, cracking, spalling. The liquid membrane helps seal and protect, especially where moisture-drive and crack bridging is required.

Surfacing Supplies & Finishes

As part of a full “floor/ wall/ surfacing” system, the membrane acts as the waterproofing base layer. Over that you may have finishes (tile, stone, microcement or other renders) — integrating waterproofing early ensures the finish lasts.

Here are frequent problems and how to avoid them:

Poor Adhesion / Bond Failure

• Cause: Substrate not properly prepared (roughened, cleaned), residual moisture too high (>3%), or applied in direct sun/overheated surface.
• Remedy: Ensure cleaning, drying, correct moisture content; avoid direct sun/overheat; do a pull test.

Pinholes / Thin Spots / Voids

• Cause: Uneven application, rolling too thin, missing corners or penetrations.
• Remedy: Apply two coats at ~0.75 mm each, inspect for pinholes/voids, re-coat where necessary. Use fabric reinforcement at joints/cracks.

Film Cure Too Rapid / Skinning Over

• Cause: High temperature (>30 °C), direct afternoon sun, rapid drying hindering bonding.
• Remedy: Apply in cooler conditions, avoid direct sun, use thinner coats, ensure good ventilation but not forced rapid drying.

Substrate Moisture or Trapped Moisture

• Cause: Applying over substrate still drying or with moisture; especially for pools/plaster or damp slabs.
• Remedy: Measure substrate moisture, allow drying; for plaster or submerged surfaces allow extra cure time; apply correct coats.

Using as Walkable Finish Without Seal

• Cause: Assuming membrane alone is trafficable without seal.
• Remedy: For trafficable surfaces (i.e. a balcony sealed with semi-clear Liquid Membrane), apply SEMCO Titan Shield Gloss..

Colour / Discolouration Issues

• Cause: Film may change colour when exposed to water if not fully cured.
• Remedy: Allow full cure (6-7 days or longer in cooler/humid conditions) before exposing to moisture. Drain and wait if applied in pool/plaster situations.

Here is how a high-quality liquid membrane like SEMCO Liquid Membrane™ compares to other common systems:

Liquid-applied elastomeric membrane (e.g., SEMCO)

• Pros: Seamless, high flexibility, many substrates, simpler detailing
• Cons: Requires careful prep; film thickness critical; not self-levelling

Sheet membrane (bituminous roll, modified bitumen)

• Pros: Large area coverage, thicker film possible
• Cons: Seams/laps are weak points; less flexible; more labor intensive

Cementitious coatings

• Pros: Easy to apply, cheaper initial cost
• Cons: Rigid, less tolerant of movement, may crack over time

Sheet + liquid hybrid systems

• Pros: Combine durability with flexibility
• Cons: May cost more; complexity of systems and layers increases

Two-part polyurethane membranes

• Pros: Very high performance, excellent chemical/UV resistance
• Cons: Higher cost; requires more skilled applicator; may have higher VOC/hazardous components

In this light, SEMCO Liquid Membrane™ offers strong flexibility, application ease, and substrate versatility — making it a compelling option especially for retrofit, DIY and multi-substrate projects.

• Elastomeric: A material with elastic properties – it can stretch and return to original shape. The SEMCO product’s high elongation means it is elastomeric.
• Seamless membrane: A waterproofing layer applied in liquid form that cures into a continuous film without joints or seams.
• Crack-bridging: The ability of a membrane to span a crack or gap in the substrate without allowing water ingress.
• Substrate: The underlying surface upon which the membrane is applied (e.g., concrete, plywood, metal).
• Trafficable surface: A surface designed to be walked on (or driven on) in service. In such cases extra seal or finish is needed atop the membrane.
• Wet-area: A part of a building where water exposure is expected (e.g., showers, laundries, balconies).
• Potable water application: Use in water intended for human consumption; our product is not currently approved for such use.
• VOC: Volatile Organic Compounds — lower VOC products are preferable for indoor air quality.
• Self-levelling: A product that flattens out under its own weight to form a smooth surface; SEMCO Liquid Membrane™ is not self-levelling.

Can I paint over SEMCO Liquid Membrane™?

Yes — a water-based paint is recommended. There are also multiple colour options in the membrane itself.

How do I ensure it has bonded to the surface?

Perform a pull test (stick tape, pull off; if membrane stays adhered, bonding is good).

Is SEMCO Liquid Membrane™ water-based and low VOC?

Yes. It is water-based and its VOC content is less than 14 g/L.

What does it feel like when dry?

It dries hard with a semi-gloss finish.

Is it only sold online?

Yes – the product is sold in Australia exclusively online via our website.

Can it be used as self-levelling?

No. It cannot be used as a self-levelling product.

Is it slippery when wet?

The membrane takes the texture of the substrate. It has no slip resistance rating on its own.

Why does the membrane discolour when in contact with water?

Discolouration is a sign the membrane has not fully cured yet — it will still function, but curing must be completed for full performance.

Is the product UV stable?

Yes. It is UV resistant.

Can it be applied over silicone?

Yes — it can be applied over products such as silicone and Sikaflex 11GC+.