Ultimate Guide to Choosing the Best Waterproof Fabrics for Your Bags

When it comes to keeping your belongings dry in unpredictable weather, waterproof bags are a must-have for a variety of people—not just outdoor adventurers. Whether you’re a commuter braving sudden downpours or a parent trying to protect your gear, the right waterproof fabric can make all the difference in a bag’s performance. However, choosing the right fabric isn’t always straightforward, given the range of options available, including PU-coated nylons, laminated membranes, and rugged canvas treatments. So, how do you pick the ideal material?

In this blog post, we will take a look at some of the top waterproof fabrics for bags, the technologies behind them, and the key factors to consider when making your choice.

What Makes a Fabric Waterproof?

To classify a fabric as waterproof, it needs to offer resistance against water penetration under pressure. This resistance is tested using a system called hydrostatic head, which measures how much water the fabric can withstand before it starts to leak. The higher the hydrostatic head, the better the fabric’s water resistance.

For instance:

• Fabrics rated at 3,000–5,000 mm can resist light rain and splashes, ideal for everyday commuting or school bags.
• Fabrics in the 10,000–20,000 mm range withstand heavy rainfall and are perfect for backpacks and travel bags.
• High-end fabrics like Gore-Tex® with ratings over 20,000 mm are made for extreme conditions, offering both high waterproofing and breathability.

Types of Waterproof Coatings and Membranes

There are two main types of waterproofing technologies: surface coatings and laminated membranes. Both come with their own benefits, depending on what you need from the bag.

1. Polyurethane (PU) Coatings

PU coatings are applied to the surface of fabrics like nylon or polyester to create a flexible waterproof barrier. They’re perfect for bags that require moderate waterproofing, such as backpacks and travel bags. They typically offer a hydrostatic head rating of 5,000–10,000 mm, providing good protection against light to moderate rain.

Advantages:

• Flexible and comfortable for everyday use
• Allows some breathability, reducing moisture build-up inside the bag

Disadvantages:

• Can degrade over time due to UV exposure and abrasion
• Less durable than other options like PVC

2. Polyvinyl Chloride (PVC) Coatings

PVC coatings create a thick, rigid waterproof layer, providing higher durability and water resistance (10,000–20,000 mm). PVC-coated bags are great for extreme conditions, such as dry bags or marine gear bags.

Advantages:

• Excellent durability and protection against chemicals, abrasion, and oils
• High resistance to UV degradation

Disadvantages:

• Heavier and less flexible than PU coatings
• Less breathable, which may lead to discomfort during extended use

3. Thermoplastic Polyurethane (TPU) Coatings

TPU coatings are more advanced than PU, offering excellent flexibility, durability, and performance in both water resistance (10,000–15,000 mm) and breathability. TPU is also more environmentally friendly than PVC, as it is recyclable.

Advantages:

• More flexible than PVC, offering both comfort and durability
• Environmentally friendly and free of harmful chemicals

Disadvantages:

• Higher cost compared to PU and PVC
• May have limited breathability compared to PU coatings

4. Laminated Membranes (e.g., Gore-Tex®)

Laminated membranes are high-performance films bonded to fabrics, offering the highest levels of waterproofing (20,000+ mm) and breathability. These are the go-to choice for technical backpacks and gear bags used in extreme outdoor conditions.

Advantages:

• Superior waterproofing combined with excellent breathability
• Ideal for high-performance gear, preventing condensation build-up

Disadvantages:

• Expensive and more complex to manufacture
• May be less durable in terms of abrasion resistance

Comparing Waterproof Fabrics

Each type of waterproof fabric comes with its own set of characteristics, and it’s important to understand how they compare in terms of weight, flexibility, and performance.

• PU-Coated Nylon: Lightweight, flexible, and breathable, suitable for everyday backpacks (5,000–10,000 mm).
• PVC-Coated Polyester: More durable and offers higher water resistance (10,000–20,000 mm), ideal for heavy-duty bags like dry bags and marine gear.
• Waxed Cotton Canvas: Provides moderate waterproofing (5,000–7,000 mm) with excellent abrasion resistance, often used for heritage-style bags.
• Gore-Tex® Laminated Fabrics: Offers industry-leading waterproofing (20,000+ mm) and breathability, perfect for technical and outdoor gear.

Selecting the Right Waterproof Fabric for Your Bag

Choosing the best waterproof fabric depends on the bag’s intended use. Let’s break down which fabrics work best for different types of bags.

• Commuter Backpacks: PU-coated nylon (5,000–10,000 mm) strikes a balance between waterproofing, flexibility, and comfort.
• Dry Bags & Submersible Pouches: For full submersion, use PVC-coated or TPU-coated fabrics (20,000+ mm) with welded seams for complete waterproofing.
• Travel Duffels: For heavy-duty use, choose PVC-coated polyester (10,000–20,000 mm) for abrasion resistance and water resistance.
• Roll-Top Backpacks: A great option for daily rain protection, using 210D PU-coated nylon or Gore-Tex® laminated fabrics (5,000–20,000 mm).
• Technical & Camera Bags: Laminated membranes like Gore-Tex® provide high waterproofing and breathability, perfect for outdoor and technical gear.

Eco-Friendly Waterproof Options

As environmental concerns grow, there are more sustainable choices available. PFC-free Durable Water Repellent (DWR) finishes, recycled PET laminates, and bio-based TPU coatings are becoming more popular. These options help reduce the environmental impact while maintaining performance.

• PFC-Free DWR Finishes: Silicone or hydrocarbon-based DWR finishes are a more sustainable alternative to traditional PFC-based treatments.
• Recycled PET & Nylon Laminates: Recycled materials offer a more eco-friendly approach to waterproofing while maintaining decent performance.
• Bio-Based TPU Coatings: Derived from castor oil, bio-based TPU coatings offer water resistance and compostability under industrial conditions.

Caring for Waterproof Bags

Maintaining the performance of waterproof bags is essential for long-lasting protection. To care for your bag:

1. Cleaning: Hand-wash with mild soap and cool water. Avoid machine drying to preserve coatings.
2. Drying: Air-dry your bag flat in a shaded area, away from direct sunlight and heat.
3. Reproofing: Apply DWR sprays or PU reproofing annually to maintain water resistance.
4. Seam and Zipper Care: Inspect and maintain sealed seams and waterproof zippers to prevent leaks.
5. Storage: Store your bag in a dry, cool area, away from direct sunlight.

Conclusion

Choosing the right waterproof fabric for your bag is crucial to its performance and longevity. Whether you need something for everyday use, outdoor adventures, or technical gear, understanding fabric ratings, coating technologies, and specific needs will help you make the best decision. By balancing waterproofing performance with comfort, flexibility, and sustainability, you can create a high-quality bag that stands up to the elements while offering lasting durability.