The Advantages and Disadvantages of Waterproofing Membranes and Liquid Waterproofing Membranes

I. Advantages and Disadvantages of Waterproofing Membranes

Waterproofing membranes are traditional mainstream materials in building waterproofing. They are categorized by material into modified bitumen type (e.g., SBS, APP membranes) and polymer type (e.g., PVC, TPO, EPDM membranes). Although the performance of these two subtypes varies slightly, their overall advantages and disadvantages share commonalities.

(I) Core Advantages

Stable physical properties and high tensile strength
As prefabricated solid materials, waterproofing membranes have standardized performance when leaving the factory. Particularly, polymer membranes (e.g., TPO, EPDM) have a tensile strength of 10–20 MPa and an elongation rate exceeding 200%, enabling them to effectively resist tensile deformation of the substrate caused by temperature changes and settlement, thereby reducing the risk of cracking.

Example: For large-area flat structures such as roofs and basement top slabs, which are prone to thermal expansion and contraction under high summer temperatures and low winter temperatures, the high tensile resistance of polymer membranes prevents the waterproof layer from breaking.

Strong durability and long service life
High-quality waterproofing membranes (e.g., SBS modified bitumen membranes, EPDM polymer membranes) exhibit excellent weather resistance and aging resistance. With proper maintenance:

Modified bitumen membranes have a service life of approximately 10–15 years;

Polymer membranes (e.g., TPO, EPDM) can last 20–30 years or longer, making them suitable for buildings with high waterproofing life requirements (e.g., public buildings, industrial plants).

Good puncture resistance and external force resistance
Waterproofing membranes have a dense structure, especially those with fiber-reinforced layers (e.g., polyester felt, glass fiber felt), which offer strong puncture resistance. They can withstand minor impacts during construction and external forces from subsequent renovations (e.g., pipe installation on roofs, root penetration in green roofs).

Applicable scenarios: Walkable roofs, green roofs, garage top slabs, and other areas vulnerable to external interference.

High construction efficiency for large areas
Waterproofing membranes come in large single-roll sizes (typically 10–20 ㎡ per roll) and can be quickly spliced via hot melting (for modified bitumen types) or bonding (for polymer types). They are suitable for large-area flat substrates (e.g., roofs of entire buildings, large basement floor slabs) and help shorten the construction period.

(II) Main Disadvantages

Stringent substrate requirements, prone to blistering/leakage
Waterproofing membranes must be installed on substrates that are flat, dry, and crack-free (substrate flatness deviation generally requires ≤ 5 mm). If the substrate is uneven or has tiny cracks, the membrane will fail to adhere tightly to the substrate, leading to blistering; accumulated water in blistered areas can cause the waterproof layer to fail over time.

Pain point: Renovating substrates of old buildings incurs high costs. Direct installation of membranes on such substrates significantly increases the risk of leakage.

Numerous seams, concentrated leakage risks
Multiple rolls of membranes need to be spliced during installation, and seams (e.g., heat-fused laps, tape-bonded joints) are weak points of waterproofing. Improper construction techniques (e.g., insufficient hot-melting temperature, inadequate lap width) or aging of seams over time can easily cause water seepage.

Data: Approximately 70% of leakage issues in membrane waterproofing layers stem from improper seam handling.

Difficult construction on complex structures
For curved or irregular structures (e.g., pipe roots, internal/external corners, elevator pits, roof gutters), membranes are difficult to fit the substrate. They require cutting, splicing, and additional reinforcement layers (e.g., auxiliary membranes, sealants), resulting in cumbersome construction steps and persistent leakage risks.

Insufficient environmental friendliness and construction convenience for some types

Hot-melt modified bitumen membranes require high-temperature heating (180–220°C) during construction, producing pungent odors and posing a risk of scalding;

Some polymer membranes (e.g., PVC) require solvent-based adhesives, which may release VOCs (Volatile Organic Compounds), affecting the environment and the health of construction workers.

II. Advantages and Disadvantages of Liquid Waterproofing Membranes

Liquid waterproofing membranes are classified by film-forming mechanism into solvent-based (e.g., polyurethane waterproofing coatings), water-emulsion-based (e.g., acrylic waterproofing coatings), and reaction-curing-based (e.g., JS composite waterproofing coatings, polyurea waterproofing coatings). Their core advantage lies in the "liquid film-forming" property, which allows adaptation to complex substrates.

(I) Core Advantages

Seamless film formation, eliminating seam leakage fundamentally
Liquid materials can be continuously brushed or sprayed on the substrate surface, forming a complete, seamless waterproof film after curing. This fundamentally avoids the weak point of "numerous seams" in membranes, making them particularly suitable for waterproofing scenarios with "small areas and multiple joints" (e.g., pipe roots in bathrooms/kitchens, junctions between walls and floors).

Strong adaptability to substrates and flexible construction
Liquid materials have fluidity and can penetrate into tiny cracks (usually ≤ 0.3 mm) in the substrate and cure there. They have low requirements for substrate flatness (deviation ≤ 10 mm is acceptable) and do not require complex substrate pretreatment.

Example: During the renovation of old bathrooms, walls and floors may have fine cracks. Brushing JS waterproofing coatings can directly cover these cracks without additional leveling; curved structures (e.g., inner walls of water storage tanks, curved roofs) can also be constructed easily.

Convenient joint handling and good waterproof integrity
For irregular parts such as pipe roots, internal/external corners, and floor drains, no cutting or splicing is needed. Thickened brushing (e.g., brushing width ≥ 200 mm and thickness ≥ 1.5 mm at pipe roots) can be directly applied to form local reinforcement layers, ensuring the waterproof film fits perfectly with the substrate and components for enhanced integrity.

High environmental friendliness and construction safety for some types
Mainstream liquid waterproofing membranes (e.g., water-emulsion acrylic coatings, JS composite coatings) are water-based materials with no or low VOC content. They produce no pungent odors during construction, do not require high-temperature heating, and are safe to operate. They are suitable for indoor enclosed spaces (e.g., residential bathrooms, kitchens) or projects with high environmental requirements (e.g., schools, hospitals).

(II) Main Disadvantages

Weak physical properties, poor tensile and puncture resistance
The tensile strength of liquid waterproof films is usually lower than that of waterproofing membranes (mostly 1–5 MPa), and their elongation rate is also relatively low (generally ≤ 150%). If the substrate undergoes significant settlement or tensile deformation (e.g., settlement period of new buildings, high-temperature expansion of roofs), the waterproof film is prone to cracking.

Pain point: If only liquid waterproofing is used for large-area roofs, cracks may appear due to substrate deformation after long-term use, requiring reinforcement layers (e.g., non-woven fabric) to improve performance.

Curing highly affected by the environment, long construction period
The curing speed of liquid waterproofing membranes depends on temperature and humidity:

When the temperature is below 5°C or humidity exceeds 85%, water-based coatings (e.g., JS, acrylic coatings) cure slowly or even stop curing;

Multiple coats (usually 2–3) are required, with each coat needing to wait for the previous one to fully cure (approximately 4–8 hours, depending on the environment). Construction efficiency for large areas is lower than that of membranes (e.g., a 100 ㎡ roof can be completed in 1 day with membranes, but takes 2–3 days with liquid coatings).

Large variation in durability, relatively short overall service life
The service life of liquid waterproofing membranes varies significantly by material type:

Low-end acrylic waterproofing coatings: Poor weather resistance, prone to aging and chalking when used outdoors, with a service life of only 3–5 years;

High-quality polyurethane and polyurea waterproofing coatings: Good weather resistance and water resistance, with a service life of 10–15 years, but still shorter than that of polymer waterproofing membranes;

Pain point: Using low-cost, low-quality products may require re-waterproofing in 3–5 years, leading to high long-term maintenance costs.

Uneven film thickness, prone to failure due to improper construction
The thickness of liquid waterproof films depends on the construction worker's brushing technique. If local brushing is too thin (below the design thickness, e.g., JS coating design thickness of 1.5 mm but actual thickness of only 0.8 mm), waterproof performance will be insufficient; if brushing is too thick, cracking and wrinkling may occur.

Requirement: A wet film thickness gauge must be used during construction, which places high technical demands on construction workers.

III. Summary of Core Differences (Comparison Table)

From the above comparison, it is clear that selection should prioritize the shape of the construction part (flat/complex), substrate conditions (new/old), and waterproofing life requirements-choose waterproofing membranes for large-area flat surfaces with high life demands; select liquid waterproofing membranes for small areas, parts with multiple joints, or uneven substrates. The two can also be used in combination (e.g., membranes for roofs + liquid coatings for joint reinforcement) to maximize waterproofing effectiveness.