Is the Roof Cargo Bag Waterproof?
Yes. A roof cargo bag is an external storage solution for vehicles, designed to withstand various weather conditions. A well-manufactured roof cargo bag should be made of waterproof materials and include design features that prevent water infiltration. When using a roof cargo bag for additional storage, one of the biggest concerns is whether it can protect your belongings from rain, snow, and other harsh weather conditions. To ensure protection, look for a waterproof roof cargo bag explicitly labeled as such. However, different roof cargo bags offer varying degrees of waterproof protection.
Next, we will explore different waterproof materials, compare their performance, and provide a buying guide to help you choose the right roof cargo bag for your needs.
Waterproof Materials and Waterproof Ratings
Several materials are commonly used for waterproof roof cargo bags:
PVC (Polyvinyl Chloride) Waterproof Fabric
PVC (Polyvinyl Chloride) waterproof fabric is a heavy-duty material with a strong vinyl coating that provides waterproofing, UV resistance, and abrasion resistance while being cost-effective. PVC can be used as the primary material for a roof cargo bag or as a coating.
Long-term durability: Over time, PVC waterproof fabric is more prone to cracking and fading, especially under intense sunlight. In low temperatures, it may become stiff and age more quickly.
Polyester Coated Fabric
Polyester is commonly used in roof cargo bags, but it is not inherently waterproof. Its waterproof properties depend on an added coating, such as PVC or PU (Polyurethane):
- PU Coating (Polyurethane):
- Enhances waterproofing while maintaining a lightweight structure.
- More flexible than PVC but less resistant to wear and tear.
- PVC Coating (Polyvinyl Chloride):
- Provides excellent waterproofing and high durability.
- Heavier and less flexible than PU coatings.
Coated Oxford Fabric
Oxford fabric is a strong and durable material that is lightweight and has good breathability. However, it is not waterproof and requires a coating to achieve waterproofing. Oxford coated fabric typically uses PVC, PU, or PA coatings.
For example, a PVC (Polyvinyl Chloride) coating creates a waterproof barrier that prevents water from penetrating the fabric. Adding a PVC coating also enhances durability, making the roof cargo bag easier to clean while preventing dirt, dust, and stains from seeping into the fabric.
Compared to other waterproof materials, the combination of Oxford fabric with a PVC coating provides a relatively cost-effective solution. PU and PA coatings offer slightly lower waterproof performance than PVC.
| Coating Type | Waterproofness | Durability | Price | Other Features |
| PVC coated Oxford fabric | Highly Waterproof | High Durability | High | Wear-resistant and tear-resistant, heavier than PU and PA coatings, less flexible, and may crack over time. Most cost-effective for long-term outdoor use. |
| PU coated Oxford fabric | Good Waterproofness | Good Durability | Mid | Breathable, lightweight, and flexible, suitable for outdoor use. Lightweight with some waterproofing, but not as durable as PVC, long-term outdoor exposure may cause coating degradation. More expensive than PA-coated fabric. |
| PA coated Oxford fabric | Basic Waterproofness | Medium Durability | Low-Mid | Lower waterproof performance, mainly used for general moisture resistance rather than complete waterproofing. |
| No Coating | Not Waterproof | Basic Durability | Low | Good breathability, not suitable for outdoor exposure |
Coated Nylon Fabric
Nylon is a robust material with excellent durability and tear resistance, lightweight, and suitable for long-term use. Nylon materials are generally lightweight, easy to install, and store. Nylon itself has some water resistance but is not as waterproof as PVC; its actual waterproof capability depends on the coating process. To enhance its waterproofness, nylon commonly uses waterproof coatings such as PVC, PU, and DWR. Some brands also use a lamination process to combine a rubber layer with a nylon layer, forming a rubber laminated nylon composite material.
| Material Type | Waterproofness | Durability | Flexibility/Breathability | Other Features | Cost |
| Rubber Laminated Nylon | Good waterproofness | High durability | Medium flexibility(Slightly stiffer than pure nylon) | Enhanced waterproofness through rubber lamination technology, more durable than regular PU-coated nylon, suitable for all-weather outdoor use. | Mid-to-high price |
| PVC-coated Nylon | Highly waterproof | High durability | Medium flexibility(Slightly stiffer than PU-coated) | Almost 100% waterproof, less flexible overall but more tear-resistant and abrasion-resistant, suitable for mid-to-high-end roof bags. | Mid-to-high price |
| PU-coated Nylon | Good waterproofness | Good durability | Good flexibility and breathability | Lighter than PVC-coated, but less durable, suitable for temporary waterproof needs. | Medium price |
| DWR-coated Nylon | Water-resistant | Basic durability | Good flexibility and breathability | Causes water to bead up and roll off, but not suitable for long-term waterproofing. | Low price |
TPU (Thermoplastic Polyurethane) Laminated Fabric
This fabric is made by laminating a layer of TPU onto a polyester substrate. TPU fabric has high tensile strength, tear resistance, and flexibility. TPU laminated fabric is generally lighter and softer than PVC, with better cold resistance. It offers good flexibility and long-term performance. However, it is more expensive and less resistant to punctures and abrasion compared to PVC.
Canvas
Canvas is lightweight and breathable, but it has low inherent waterproofness. Canvas typically requires additional waterproof treatments, such as wax coating, to provide better waterproofness in outdoor applications. Therefore, canvas is not commonly used for roof bags, and very few brands adopt this material. It is not suitable for prolonged exposure to rain.
- Waxed Canvas: Provides some water resistance but needs regular maintenance.
- Oilcloth Canvas: More water-resistant but heavier and less durable than modern synthetic materials.
Other Specialized Materials
For example, Cordura fabric, which is woven from INVISTAโข yarns and distinct from imitation materials, is a highly abrasion-resistant nylon fabric often used in military and tactical gear. Cordura fabric is renowned for its exceptional strength, tear resistance, and durability, making it a top choice for outdoor and tactical equipment. However, it is not naturally waterproof; Cordura’s waterproof capability relies on coatings rather than the material itself. All Cordura fabrics have a polyurethane coating on the back and a waterproof coating on the front, making them suitable for all-weather use.
Laminated Multi-Layer Fabrics: Some brands use advanced lamination techniques to enhance waterproofing while maintaining flexibility.
Comparison of Waterproof Materials
| Material Name | Waterproof Level | Abrasion Resistance | Flexibility | Main Coating Technology | Price | Advantages | Disadvantages |
| PVC Fabric | Completely Waterproof | High | Relatively Hard | No Coating Needed | Medium | Strong Waterproofing, Abrasion-Resistant, Affordable | Becomes Hard in Low Temperatures, May Crack Under Prolonged UV Exposure |
| PU-Coated Polyester Fabric | Medium Waterproof | Moderate | Soft | PU Coating | Relatively High | Lightweight, Soft, Excellent Cold Resistance | Waterproof Ability Decreases Over Time, Slightly Lower Abrasion Resistance Than PVC |
| Oxford Cloth with Coating | Good Waterproof | High | Moderate | PVC, PU, PA Coating | Medium | Good Abrasion Resistance, Coating Enhances Waterproofing, Affordable | Not Waterproof on Its Own, Completely Relies on Coating |
| Nylon Coated Fabric | Good Waterproof | High | Lightweight and Soft | PVC, PU, DWR Coating | Relatively High | Lightweight, Tear-Resistant, Suitable for Long-Term Use | Limited Waterproofing on Its Own, Requires Coating for Enhancement |
| Rubber Laminated Nylon | Completely Waterproof | High | Moderate | Rubber Lamination | High | Extremely Waterproof, Suitable for Harsh Weather | Rubber Layer May Deteriorate, Relatively Heavy |
| TPU Laminated Fabric | Good Waterproof | High | Very Soft | TPU Lamination | High | Lightweight, Cold-Resistant, Tear-Resistant | Expensive, Less Puncture-Resistant Than PVC |
| Cordura | Water-Repellent | Extremely High | Moderate | PU + Waterproof Coating | High | Excellent Tear Resistance, Highly Durable | Not Waterproof on Its Own, Requires Additional Coating |
| Canvas | Not Waterproof | High | Relatively Hard | Wax Coating, Oilcloth Treatment | Low | Breathable, Vintage Style | Requires Frequent Maintenance, Not Suitable for Long-Term Outdoor Use |
Therefore, if you need a roof bag with the highest waterproofness, PVC waterproof fabric and Rubber Laminated Nylon are the best choices, suitable for all-weather roof bags. If you need a lightweight, soft, and waterproof roof bag, choose PU-coated nylon or TPU laminated fabric, suitable for lightweight travel. If you need durability and some waterproofness in a roof bag, choose nylon-coated fabric or Oxford cloth-coated fabric, which offers good value and is suitable for daily use. If you need extreme abrasion resistance, something like Cordura might be more suitable for you.
Additionally, it’s worth noting that IPX ratings and fabric density parameters can also serve as reference indicators for your selection. Some suppliers may display these parameters, and you can also ask them actively to determine how waterproof, abrasion-resistant, and strong the bag is.
Waterproof Ratings: IPX Standard
| IPX Rating | Waterproof Description | Applicability |
| IPX4 | Prevents splashing from any direction but not heavy rain | Suitable for lightly waterproof roof bags, limited protection. Only suitable for small rain; water may penetrate if exposed to heavy rain for long periods. |
| IPX5 | Resists low-pressure water jets from any direction | Common standard for waterproof roof bags, suitable for moderate rain or short-term heavy rain. |
| IPX6 | Resists strong water jets from any direction | Common standard for waterproof roof bags, higher waterproofing, suitable for harsh weather. |
| IPX7 | Can withstand immersion in 1 meter of water for 30 minutes | Completely waterproof, but roof bags typically do not require this level. |
Some suppliers provide IPX ratings for their roof cargo bagsโcheck these specifications before purchasing.
Fabric Density (Denier Rating – D)
Denier (denoted by the unit D) is primarily used to measure the thickness and weight of fibers, which indirectly relates to the material’s durability and strength. Common fabric densities are as follows:
| Denier (D) | Characteristics | Applicability |
| 500D | Lightweight, Soft, Moderate Durability | Suitable for lightweight roof bags but has lower tear resistance. |
| 600D | Balances Lightness and Durability, Common Standard | Provides good durability and relatively light weight. Suitable for general highway travel. |
| 900D | Thicker, More Tear-Resistant, Heavier | Suitable for heavy-duty roof bags, higher abrasion resistance. Increases weight. |
| 1000D and Above | Extremely Abrasion-Resistant but Heavier | Suitable for extremely harsh environments but less common for regular roof bags. |
Note that a higher Denier value does not necessarily mean better waterproofness; waterproofing still relies on coatings like PVC, PU, or TPU. If you prioritize lightweight, 600D is a good choice; if you focus on durability, 900D is more reliable.
The waterproof rating and fabric density are not absolute standards for determining whether a roof bag is waterproof and durable. Some manufacturers use composite materials (such as 600D Oxford cloth with PVC coating), which cannot be measured solely by IPX or Denier.
When purchasing, do not rely solely on IPX or Denier; consider the material, coating, and actual usage needs. Additionally, the shape and detailed design of the roof bag also impacts its performance.
Design Features for Waterproofing
Strap Shape and Waterproof Optimization Design
Whether the outer layer of the straps has a waterproof coating, such as a TPU coating, can reduce water absorption. The width and thickness of the straps also matter; wider and thicker straps are less likely to be completely saturated by rain, reducing the risk of seepage.
The attachment to roof bags often involves passing straps through the interior of the vehicle, which can allow water to flow along the straps and into the vehicle. Some roof bags have straps that are secured using hooks that attach to the weatherstripping above the doors, preventing water from entering the vehicle.
Closure Design
The closure method of a roof bag is crucial for its waterproofness. A well-designed closure can ensure that water does not easily seep in.
| Closure Method | Waterproof Performance | Advantages | Disadvantages |
| Regular Zipper (No Waterproof Design) | Low | Affordable, Easy to Use | Prone to Water Entry |
| Waterproof Zipper (with Rubber Seal) | High | Effectively Prevents Water Penetration, Costly, May Be Slightly Harder to Open | Higher cost, may be slightly harder to pull |
| Double-Layer Waterproof Design (Zipper + Velcro) | Very High | Double Protection, More Secure, Slightly Increases Difficulty in Opening | Slightly increases the difficulty of opening |
| Roll-Top Closure | Extremely High | Completely Prevents Water Entry, Suitable for Extreme Weather, Less Convenient Than Zippers | Opening is not as convenient as zippers |
It is best to choose a roof bag with a waterproof curtain.
Roof Bag Shape Design
A streamlined design allows rainwater to slide off quickly, reducing the risk of water accumulation, while a flat-top design tends to collect water, which is unfavorable for drainage.
Seam Construction
For the seams and joints of the roof bag, it is recommended to use high-frequency voltage bonding instead of traditional sewing techniques, which provides safer waterproofing.
Conclusion
When choosing a waterproof roof cargo bag, selecting the right material, waterproofing technology, and design features is crucial. PVC and Rubber Laminated Nylon offer the highest waterproof protection for extreme weather conditions, while PU-coated Nylon or TPU-laminated fabric provides a balance between lightweight design and waterproofing. Additionally, factors like seam welding, closure design, and strap placement significantly impact the overall water resistance of a cargo bag.
For buyers looking for a fully waterproof solution, prioritize:
- Material: PVC-coated or Rubber Laminated Nylon
- Closure: Roll-top or double-sealed zipper with a storm flap
- Seams: High-frequency welded seams over stitched ones
- Straps: Waterproof-coated straps to prevent water seepage
Understanding these factors will help ensure your belongings stay dry, even in heavy rain or extreme conditions.
