The market is flooded with dozens of products that promise affordable, durable solutions. But they are not all equally effective, and they do not suit every situation.
Roof insulation with liquid-applied materials is one of the most talked-about waterproofing options of recent years. They are easy to apply, need no torch and seem affordable. But that is exactly why many people end up making the wrong choice: ease of application does not mean they suit every roof.
In this guide you will learn exactly what liquid-applied materials are, when they are suitable and when they are not, which characteristics make a product reliable, how they compare with bitumen membranes and what you should ask a contractor for.
What Are Liquid-Applied Roof Waterproofing Materials?
Liquid-applied waterproofing materials are applied with a roller or brush directly onto the roof surface, creating an elastic membrane that stops water getting in. Unlike bitumen membranes, which are laid with a torch, liquid-applied materials cure with atmospheric moisture or air-dry, forming a continuous, seamless membrane.
1. Polyurethane
The best choice for roofs
They offer excellent elasticity, UV resistance and a long service life. Only products certified to ETAG 005, such as Hyperdesmo Classic, are suitable for primary roof waterproofing.
Suitable for:
- Roofs with cracks and leaks
- Surfaces under heavy UV stress
- Renewing existing insulation
Advantages:
- Elasticity of over 400%
- Resistant from -40°C to +90°C
- Vapour-permeable
- Heat-reflective (white)
Roof Waterproofing with Hyperdesmo
2. Acrylic
A more economical solution, suitable mainly for maintaining old insulation or as auxiliary materials
Suitable mainly for maintaining old insulation or as auxiliary materials. Not recommended for primary roof waterproofing, despite their low cost.
Suitable for:
- Maintenance of existing insulation
- Auxiliary application
Limitations:
- Lower elasticity
- Shorter service life
- Not ETAG 005 certified
3. Hybrid and silane-based
Intermediate options with characteristics that vary by product
Characteristics vary by product. Some are ETAG 005 certified and suitable for primary waterproofing. Before choosing any of them, ask for the technical data sheet.
Suitable for:
- Product-specific applications
- Combined solutions
What to check:
- ETAG 005 certification
- Climate zone (M or S)
- Consumption in kg/m²
For a full picture of the waterproofing options available, read the complete roof insulation guide.
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When Are Liquid-Applied Materials Suitable?
Liquid-applied materials are the right choice in the following cases:
- Roofs with many penetrations (air conditioners, pipes, aerials, solar panels) where laying bitumen membranes is difficult
- Roofs in good condition that need their waterproofing renewed
- Small areas and balconies
- Repairing localised damage and cracks in existing insulation
- Maintaining older waterproofing
- As a complementary application alongside bitumen membranes, at the tricky points around penetrations
When Are Liquid-Applied Materials NOT Suitable?
This is the point most people overlook, and it is just as important as knowing when they are suitable. There are cases where applying them will almost certainly fail:
- On lightweight concrete such as foam concrete or perlite concrete: these loose substrates do not provide the adhesion required and lead to blistering and delamination
- On a damp substrate: if substrate moisture exceeds 4%, curing is not completed properly and the material fails
- On roofs with extensive damage to the concrete: the substrate must be repaired first
- As the only solution in a new build without thermal insulation: liquid-applied materials do not replace a complete roof thermal insulation and waterproofing system
- When the roof has extensive delamination of old bitumen membranes: applying a liquid-applied coating on top without stripping them will fail
Which Liquid-Applied Materials Are Really Suitable for Roofs?
Here is an important point that is rarely mentioned: although the market offers dozens of liquid-applied products, only a handful are certified to ETAG 005, the European guideline that applies specifically to liquid-applied roof waterproofing.
Products without this certification may be reliable as concrete protection or as auxiliary materials, but they are not intended for primary roof waterproofing. Among the most widely used ETAG 005 certified products on the Greek market are Hyperdesmo, Sikalastic 612 and Mariseal 250.
Before choosing any liquid-applied product, ask to see the technical data sheet and check whether it mentions ETAG 005 certification.
What Makes a Liquid-Applied Product Reliable?
Beyond certification, quality liquid-applied products stand out for the following characteristics. It is worth checking them before you decide:
- Chemical base
Polyurethane products are superior thanks to their elasticity and UV resistance. Other bases may yellow or lose their elasticity over time, requiring more frequent maintenance.
- Elasticity and crack bridging
The material must stay flexible at temperatures from -40°C to +80°C and bridge hairline cracks without breaking. Concrete contracts and expands with temperature changes, and the coating must move with it.
- Service life
Reliable liquid-applied products have a service life of 10–12 years, provided they are applied correctly and maintained every five years.
- Consumption per square metre
Actual consumption ranges from 1.5 to 3 kg/m² and has a significant effect on the final cost. Low consumption of a cheap product means a thin layer that does not protect well enough. Always ask to be shown the specified consumption on the technical data sheet.
- Complementary materials
A complete system requires an adhesion primer, reinforcement at vulnerable points and an aliphatic top coat for UV protection. If someone suggests only the liquid-applied coating without these, it is a serious warning sign.
- Climate zone
Each product states which climate zone it is suitable for (M = moderate, S = severe). Using a product in the wrong zone significantly reduces its performance.
Liquid-Applied Materials vs Bitumen Membranes: When Should I Choose Which?
The most common question is whether liquid-applied materials are better than SBS bitumen membranes. The answer is not simple, because it depends on the condition and needs of each roof.
Choose a liquid-applied product when:
- The roof has many penetrations and complex geometry
- You need to renew existing insulation without stripping it
- The area is small (balcony, small roof)
- You want quick application without heavy works
Choose SBS bitumen membranes when:
- You are insulating a roof from scratch
- You need a maximum service life of 25–30 years
- It is a large area with good access
- The roof has serious damage that requires stripping
In many cases the two systems are combined: bitumen membranes on the main surface and a liquid-applied product (Hyperdesmo PB1K) at the tricky points around penetrations and joints. This is often the best combination.
Roof Waterproofing with Bitumen Membranes
Stages of Applying Liquid-Applied Waterproofing Materials
Correct application is just as important as choosing the material. Poor application can ruin even the best product.
- Inspecting and preparing the substrate
Sanding, high-pressure water jetting and removal of loose areas. Checking substrate moisture with a dedicated meter is mandatory: it must be below 4% before any application.
- Repairing cracks and vulnerable points
Opening up and sealing cracks with polyurethane sealant. Special attention to gutters, parapets and points where pipes or railings pass through.
- Priming
Applying the appropriate primer, polyurethane or epoxy depending on the substrate and the liquid-applied product that will follow. Without primer the necessary adhesion is not achieved and the material will come away.
- Reinforcement (geotextile)
Laying reinforcing fabric at corners, parapets, gutters, joints and around all penetrations. Reinforcement is not optional at these points; it is essential.
- Applying the 1st coat
Even application with a roller at the consumption rate specified in the manufacturer's technical data sheet.
- Applying the 2nd coat
At right angles to the first, for a single, continuous membrane with no weak spots.
- Protective aliphatic top coat
Essential for polyurethane products, which tend to yellow when exposed to UV. It preserves the whiteness, reflectance and mechanical properties of the material for years.
The Most Common Mistakes That Ruin the Application
Most failures of liquid-applied products are down not to the product but to the application. The most common mistakes we see in practice:
- Application on a damp substrate or an unsuitable substrate such as foam concrete
- Skipping the primer or using the wrong primer, which is not compatible with the liquid-applied product
- Applying at too low a consumption rate, creating a layer of insufficient thickness
- Leaving out reinforcement at vulnerable points
- Leaving out the protective UV top coat, resulting in rapid ageing
- Application in unsuitable weather conditions, below 5°C or in high humidity
- Not respecting the waiting times between coats
- DIY application without technical training
The last point deserves particular attention. Although liquid-applied products look easy to use, poor application can fail as early as the first winter, with repair costs far higher than the original cost of applying it correctly.
Key Points
- Liquid-applied materials do not suit every roof. Choosing them requires an assessment of the substrate.
- Only products certified to ETAG 005 are suitable for primary roof waterproofing.
- Application on a substrate with moisture above 4% almost always leads to failure.
- Primer, reinforcement and a protective UV top coat are not optional. They are essential parts of the system.
- In many cases the best combination is bitumen membranes on the main surface and a liquid-applied product at the tricky points.
- Poor application costs far more than doing it right from the start.
What We Use at Goumas Insulation
At Goumas Insulation we apply Hyperdesmo Classic, a one-component polyurethane liquid-applied waterproofing coating that cures with atmospheric moisture, forming a single seamless membrane.
The technical characteristics that make it stand out:
- ETAG 005 certification for roof waterproofing
- Elasticity of over 400% that follows substrate movement and cracks
- Resistance to UV and to temperatures from -40°C to +90°C
- High adhesion to concrete of over 2 MPa without additives
- Tensile strength of over 8 MPa
- Vapour permeability that prevents blistering from trapped moisture
- The white colour with high heat reflectance reduces heat load during the summer months
We always apply it with a polyurethane primer, geotextile reinforcement at vulnerable points and an ADY-E / ADY 500 protective aliphatic top coat, in line with the manufacturer's technical specifications. Maintenance every five years keeps the system performing at its best.
Request a Technical Assessment
If you are considering roof waterproofing with liquid-applied materials, the first step is an on-site assessment. Every roof has different needs, and the right solution can only be determined after an inspection. In some cases liquid-applied materials are the ideal choice, in others SBS bitumen membranes, and in many a combination of the two.
With 25+ years of experience in roof insulation, certified crews and a written guarantee for every project, Goumas Insulation will make sure you get the right solution for your roof.
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Price List
Frequently Asked Questions about Roof Insulation with Liquid-Applied Materials
Can I apply a liquid-applied product over old bitumen membranes?
It depends on their condition. If the old bitumen membranes are sound and have no trapped moisture, some liquid-applied products can be applied over them after suitable preparation. If there is delamination or trapped moisture, they must be fully stripped first.
How much does waterproofing with liquid-applied materials cost?
The basic system with Hyperdesmo starts from €25/m² (plus VAT), while the full reinforced system with primer, reinforcement and protective top coat starts from €30/m². See our price list for detailed prices.
How long does application take?
For a typical roof, application is completed in 3–5 days depending on the area and the weather conditions.
Does it need maintenance?
Yes. Renewal every five years is recommended to maintain maximum UV protection and reflectance.
When is the best time of year to apply it?
Ideally spring and summer (April to October). It requires a temperature above 5°C, no rain and substrate moisture below 4%.
Can I do it myself?
It is not recommended. Liquid-applied materials require correct substrate preparation, the right primer, adherence to consumption rates and technical training. Poor application will fail very quickly, with repair costs much higher than the original cost.
