Flat roof waterproofing with liquid sealant and polyester fleece – step-by-step construction
Modern flat roof waterproofing systems are implemented using different materials – for example polyurethane, PMMA or bitumen.
Regardless of the sealing system used, one component remains almost always the same: the reinforcing fleece made of polyester.
In the following example, we show the typical construction of a flat roof waterproofing system using liquid waterproofing and polyester fleece – step by step.
System structure of a liquid waterproofing system
The construction of a flat roof waterproofing system using liquid waterproofing typically consists of several steps:
Preparing the substrate
Priming of the roof surface
Reinforcement of connections and details
First sealing layer
Full-surface reinforcement with polyester fleece
Second sealing layer
Step-by-step implementation
Step 1 – Preparing the substrate
In the first step, the existing tile surface is carefully prepared and coated with the first layer of liquid waterproofing.
This layer ensures a uniform base seal and forms the basis for further construction.
Transitions, edges and connections are particularly critical and must be completely covered.
Step 2 – Primer
After cleaning, a suitable Primer applied.
The primer improves the adhesion between the substrate and the sealant and ensures a uniform surface.
Different primers are used depending on the system.
Step 3 – Reinforcing the connections
Particularly critical areas of a roof seal are:
• Wall connections
• Inside and outside corners
• Penetrations
• Transitions between components
These areas will be addressed first.
First, a sealing layer is applied.
Then Polyester reinforcing fleece embedded in the fresh coating.
This creates a flexible and crack-bridging detail seal.
Step 4 – First sealing layer
Once the details have been prepared, the sealant is applied to the entire roof surface.
In this example, a Polyurethane liquid sealant used.
The first layer serves as a base for reinforcement with fleece.
Step 5 – Full-surface reinforcement with polyester fleece
As long as the sealant is still fresh, the Polyester reinforcing fleece embedded in the coating.
The fleece sheets are laid across the entire roof surface.
The following is important:
• complete saturation of the fleece
• Bubble-free application
• Overlap of the lanes
The overlap is at least 5 cm.
The fleece absorbs part of the sealant and forms a stable, flexible reinforcement layer.
Step 6 – Second sealing layer
After the reinforcing fleece is laid, another sealing layer is applied.
This top layer completely covers the fleece and forms a closed, waterproof surface.
Depending on the system, an additional third layer may be required.
Finished layer structure
The finished roof waterproofing consists of several functional layers:
concrete substrate
primer
first sealing layer
polyester fleece
second sealing layer
This system enables a permanent and flexible sealing of flat roofs.
Why use 120 g/m² polyester fleece for liquid waterproofing?
Polyester fleece with a basis weight of 120 g/m² offers the optimal combination of flexibility, stability and impregnation capacity for high-quality Liquid waterproofing outdoors.
In contrast to conventional nonwovens of the same basis weight, this SA Building Materials Polyester Fleece 120 g/m² additionally sewn with threads.
This stitching increases the Tensile and tear strength clearly and gives the geotextile exceptionally high mechanical strength – a crucial advantage when Terraces, balconies and roof areas.
The sewing process simultaneously creates a targeted perforation the non-woven structure.
This perforation improves the Impregnation with liquid sealants, so that the material is completely embedded and a homogeneous, crack-bridging sealing layer is created.
The result is a highly resilient, durable and certified sealing fleece, whose material properties have been confirmed by independent tests (SGS).
Note regarding roll width:
The appropriate roll width depends on the area of application and the details on site – e.g. surfaces, connections or penetrations.
Crack-bridging & flexible
Reliably absorbs movements of the substrate and reduces stress cracks in the waterproofing – ideal for permanently stressed terraces and balconies.
Sewn and particularly tear-resistant
The additional stitching ensures exceptionally high tensile and tear strength and increases the service life of the entire sealing structure.
Perfectly soakable
The perforated structure allows for complete impregnation with liquid sealants and ensures a safe, homogeneous sealing layer.
Which widths of polyester fleece are used?
Different widths of polyester fleece are used for sealing work.
The choice of width depends on the specific application.
15 cm width
Used for:
• Corners
• small details
• Penetrations
• Transitions between components
25 cm width
Commonly used for:
• Wall connections
• Transitions between roof and wall
• medium detail areas
35 cm width
Typical application:
• larger connection surfaces
• Parapet connections
• Transitions at technical structures
50 cm width
For the reinforcement of the entire roof surface
Overlap of the nonwoven fabric strips
When laying the fleece, the individual strips must overlap.
Recommended overlap:
at least 5 cm
This creates a continuous reinforcement without weak points.
Typical areas of application
Polyester reinforcing fleece is used in:
flat roofs
balconies
Terraces
Parapet connections
Detailed sealing
Diploma
Polyester reinforcing fleece is a key component of modern liquid waterproofing systems.
The combination of liquid waterproofing and reinforcing fleece creates a flexible, durable and crack-bridging waterproofing system that is used on flat roofs, terraces and balconies.
The appropriate reinforcing fleece for this application
For flat roofs, terraces and balconies, it has proven effective. SA Building Materials Polyester Fleece 120 g/m² Proven as a reliable reinforcement for liquid waterproofing systems.
The material ensures a crack-bridging and durable sealing layer – ideal for permanently stressed roof surfaces.
✔ crack-bridging
✔ Perfectly soakable
✔ High tear resistance