Loose Laid Waterproofing Membranes: Types, Usage, Advantages and Benefits

What are Loose Laid Waterproof Membranes?

Loose laid waterproof membranes are sheet waterproofing membranes that do not adhere to the substrate directly. Instead, these membranes are loosely laid over the surface and held in place by the weight of the overlaying layers, such as gravel, pavers, mechanical fasteners, or other ballast materials. The properties of the loose laid waterproofing depend on the type of sheet membrane.

The most used loose laid waterproofing membranes are EPDM (Ethylene propylene diene monomer), bituminous, and HDPE (High-density polyethylene). Loose-laid membranes are used due to their ease of installation, cost-effectiveness, ease of repair and replacement, enhancing protection against extreme weather conditions, and potential for reuse and recycling.

What are the 7 Types of Loose Laid Waterproof Membranes?

Loose laid waterproofing systems are mainly of 7 types, each loose laid type has unique characteristics and suitable applications.

7 Types of Loose Laid Waterproof Membranes

1. EPDM waterproof membrane
2. PVC water waterproof membrane
3. TPO waterproof membrane
4. HDPE waterproof membranes
5. CSPE waterproof membranes
6. Butyl Rubber waterproof membranes
7. Bituminous waterproof membranes

Read more: 10 Types of Waterproof Methods: Properties, Applications, Advantages, and Maintenance

1. EPDM waterproof membranes

EPDM (Ethylene Propylene Diene Monomer) membrane is a synthetic rubber, loose-laid waterproof membrane. EPDM loose laid membranes consist of higher durability, flexibility, water resistance, and UV resistance. Hence, it can be used on roofing, basements and foundations, terraces and balconies, ponds, underground structures, and large commercial applications.

2. PVC waterproof membranes

PVC (Polyvinyl Chloride) membrane is a thermoplastic loose-laid waterproof membrane. PVC loose-laid membranes consist of higher strength, flexibility, UV resistance, and resistance to chemicals and fire, and offer weldable seams for airtight installations. Hence, it can be used in roofing, terraces, ponds, tunnels, tanks, and in industrial and commercial applications

3. TPO waterproof membranes

TPO (Thermoplastic Polyolefin) membranes are a single-ply reflective membrane made from a blend of polypropylene and ethylene-propylene rubber. TPO loose-laid membrane is resistant to UV and chemicals, energy efficient due to its reflective properties, and has heat-weldable seams. Therefore, it can be used in terraces, underground structures, and roofing, especially in environmentally friendly “cool roof” systems.

4. HDPE waterproof membranes

HDPE (High-density Polyethylene) membrane is a thermoplastic membrane. HDPE loose-laid membranes are highly flexible, puncture-resistant, resistant to chemicals, have long-term durability, and consist of high tensile strength. Accordingly, they can be used in landfill liners, pond liners, roofs, foundational walls, and tunnels.

5. CSPE waterproof membranes

CSPE (Chlorosulfonate Polyethylene) membranes are synthetic rubber membranes. CSPE loose-laid membranes are durable, resistant to environmental factors like UV rays and temperature extremes, and resistant to chemicals. Hence, these can be used on roofing, containment liners, tanks, and tunnels.

6. Butyl Rubber waterproof membranes

Butyl rubber membranes are made from synthetic rubber known for its impermeability and elasticity. Butyl membranes consist of higher flexibility, are resistant to UV and ozone, and have excellent weatherability. Therefore, these membranes are used in roofing, pond liners, tank liners, and in reservoirs.

7. Bituminous waterproof membranes

Bituminous loose-laid refers to a waterproofing system where sheet membranes made of bituminous materials (like asphalt or coal tar) are installed without being fully adhered to the substrate, relying instead on the weight of an overlaying material for ballast.

Where to Use Loose-Laid Waterproofing Membranes?

Loose-laid waterproofing can be used for waterproofing roofs, basements and foundations, ponds and water features, terraces and balconies, and tunnels and subways are five of the places where you can use loose-laid waterproof membranes.

Roof waterproofing using loose-laid waterproofing

You can use loose-laid membranes like PVC, EPDM, TPO, and HDPE on the roofs. Roofs always get wet, contract, and expand due to temperature fluctuations, which causes damage to adhered waterproof systems.

In order to prevent this, you can use loose-laid waterproof membranes because loose-laid waterproof membranes are highly flexible, durable, and easy to repair when used on roofs.

Basement, crawlspace, and foundation waterproofing

EPDM, PVC, and TPO are loose-laid membranes you can use for basement , crawlspace, and foundation waterproofing. Water infiltration into the foundation due to rainy conditions causes basements to get damp, which results in structural damage, mold, and mildew growth, and leads to health issues for the users.

To prevent this, you can use loose-laid waterproof membranes since these membranes are easy to install and repair, and they enhance durability.

Ponds and water features waterproofing

You can use PVC or Butyl rubber membranes as loose-laid membranes on ponds, especially on pond liners. Water is a constant factor in ponds and water features, which can cause to soil erosion around the pond edges and affect the health of plants surrounding the areas where water leaks can occur.

Therefore, to prevent this, you can use loose-laid waterproof membranes as they are highly flexible, cost-effective, and ensure effective water containment.

Terraces and balcony waterproofing

PVC and TPO loose-laid membranes are good choices for waterproofing balconies and terraces. Terraces and balconies can get wet by wind-driven rain and water escaping through joints, seams, and gaps, staining walls and ceilings below the terraces and balconies, and also cracks in the concrete.

In order to ensure the safety of these areas, you can use loose-laid waterproof membranes because they are flexible and have good seam strength, extending the life span of terraces and balconies.

Tunnels and subway system waterproofing

HDPE, and Butyl membranes are often used in waterproofing tunnels and subway systems. Through inadequate drainage systems or construction defects, water can enter, posing safety issues to the users and damaging the electrical systems and equipment.

Therefore, you can use loose-laid waterproof membranes to prevent these damages since these membranes are adaptable and resistant to hydrocarbons and other chemicals.

How to Install Loose Laid Waterproofing?

Loose-laid waterproofing membrane can be installed as the step-by-step guide below.

1. Surface preparation : First, you should clean the surface to remove debris, oil, laitance, and sharp objects. You must ensure the surface is dry and smooth before installing. You should make sure there is a surface angle to remove surface water.
2. Position the waterproofing membrane : Then, unroll the loose laid membrane (e.g., HDPE, PVC, or EPDM) across the surface with proper overlaps (typically 100-150 mm).
3. Seal overlaps : After unrolling and measuring the distance, you should use double-sided tape, welding, or adhesive strips to secure the overlaps, depending on the membrane type.
4. Install termination bars or edge restraints : Then, anchor the membrane edges at walls or perimeters to prevent displacement while installing.
5. Conduct flood testing : Before the membrane is covered with screed, insulation, or a protection board, test the layer for leaks by performing a 24-48 hour water ponding test.
6. Protect with screed or protection board : Cover the membrane with a concrete screed, insulation, or protection board to prevent mechanical damage.

What is the Strongest Loose Laid Waterproofing Membrane?

The strongest loose laid waterproofing membrane is HDPE (High-Density Polyethylene). HDPE membranes have tensile strength ratings of over 16 MPa (2,300 psi) and can resist aggressive soil chemicals, petroleum products, and organic solvents. Its thickness can range from 1.5 mm to 2.5 mm. Hence, HDPE waterproofing is especially used in critical substructure waterproofing applications such as foundation slabs, retaining walls, tunnel floors, and basement rafts.

How to Seal Loose Laid Membranes Overlaps?

The loose-laid membrane overlaps must be sealed mechanically or chemically.

To mechanically seal the loose-laid membranes, you can use hot wedge welding or hot air welding to fuse overlapping sheets. You should maintain at least 100mm (4 inches) overlap, and it can be applied with PVC and HDPE membranes.

Loose membranes, such as EPDM, can’t be welded. In this case, you can use seam tapes, primer-activated adhesives, or pressure-sensitive flashing strips to bond the seams. You should overlap the sheets by 150 mm (6 inches) and firmly roll them using a silicone roller to eliminate air pockets and ensure full adhesion.

How Long Can a Loose Laid Waterproofing Last?

A properly installed loose laid waterproofing system can last over 30 years. The lifespan of the loose laid depends on several key factors like membrane material, site condition, UV exposure, mechanical protection, and installation quality.

The most durable loose laid waterproofing membrane is EPDM (Ethylene Propylene Diene Monomer). The durability of EPDM waterproofing comes with exceptional elasticity, UV resistance, ozone resistance, and the ability to handle thermal expansion and contraction without cracking. EPDM is especially installed on large horizontal surfaces like basement slabs, green roofs, inverted roofs, and tunnel floors.

What are the 5 Benefits of Loose Laid Waterproof Membranes?

Ease of installation, cost-effectiveness, flexibility in design and construction, potential to reuse and recycle, and versatility are the 5 advantages of loose laid waterproof membranes.

1. Ease of installation: Loose-laid waterproof membranes are easier and faster to install compared to fully adhered membranes. Hence, using loose-laid membranes on the substrate can reduce installation time and require minimal skills and tools, thereby minimizing the installation cost.
2. Cost-effective: Loose-laid membranes are cost-effective in terms of material cost and installation expense. Therefore, using loose-laid waterproof membranes can reduce the project cost of installing these membranes, increase the project efficiency, and is financially flexible.
3. Flexibility in design and construction: Loose-laid membranes can easily adapt to irregular surfaces and are adaptable compared to fully attached membranes. Because of that, using loose laid membranes can promote the safety and comfort of the occupants, be easy to repair and maintain, and lead to improved energy efficiency.
4. Potential for reuse and recycling : Loose-laid membranes are made up of materials that can be recycled and do not leave any adhesive residue; therefore, the membranes can be reused compared to fully adhered membranes. Hence, using loose-laid waterproof membranes can reduce the demand for virgin materials, conserving natural resources like petroleum, and also help to reduce the volume of construction waste.
5. Versatility of usage: Loose-laid membranes can be used in a wide range of applications such as roofs, tunnels, ponds, terraces, and reservoirs, and are also adaptable on a wide range of substrates, making them more versatile than fully attached membranes. Therefore, using loose-laid waterproof membranes makes it easy to furnish and repair and ensures a high return in investment over time, which saves long-term costs.

What are the 5 Disadvantages of Loose Laid Waterproof Membranes?

Below are five disadvantages of loose laid waterproof membranes.

1. Loose-laid waterproof membranes can be damaged by the wind and temperature fluctuations, which affect the effectiveness of the membrane.
2. Loose-laid waterproof membranes have compatibility issues between membranes and other building materials due to adhesiveness
3. Loose-laid waterproof membranes require a larger labor force and time to install, and it depends on the location.
4. Premium loose-laid waterproof materials consist of a higher initial cost.
5. Rising environmental concerns when disposing of loose-laid waterproof membranes containing materials.