ShadeMart 17ft x 21ft Black Sun Shade Sail UPF50 Rectangle

In this review of the ShadeMart 17' x 21' Black Sun Shade Sail, the bottom line is simple: this is a practical, heavy-duty rectangle canopy for anyone who needs effective sun protection without trapping heat. The reviewer found it especially useful for patios, carports and boat covers because the woven HDPE fabric blocks up to 95% of harmful UV while remaining breathable and water permeable. Installation requires basic hardware, but once in place the sail noticeably lowers temperature and provides large, even coverage.

Key Features

• Material: Woven HDPE fabric provides a durable, tear-resistant surface that holds up to wind and sun exposure.
• UV Protection: Blocks up to 95% of UV rays to reduce sun exposure and lower ambient temperatures under the canopy.
• Breathability: Water permeable construction allows rain and air to pass through, preventing pooling and reducing wind lift.
• Hardware Ready: Stainless steel D rings attached to heavy duty white webbing create secure anchor points for common mounting kits.
• Custom Sizing: Available in multiple sizes so buyers can choose a rectangle to fit patios, carports, pergolas or boats.

Who It's For

This shade sail is best for homeowners and hobbyists who need a large, breathable sun canopy for outdoor living areas, carports, poolside lounges or boats. It is a good choice where airflow and water permeability are important to avoid heat buildup and standing water.

Those seeking a fully waterproof shelter or a hard-roof carport replacement should look elsewhere, since this fabric is intentionally permeable and not rated as waterproof. Also, shoppers who want a pre-installed permanent structure may prefer a rigid awning rather than a tension-mounted shade sail.

Pros & Cons

Pros

• Effective UV protection that noticeably cools covered areas and protects surfaces from sun damage.
• Durable construction with stainless steel D rings and heavy webbing for secure mounting.
• Breathable, water permeable fabric prevents pooling and reduces wind strain compared with solid tarps.
• Easy to install with standard hardware and adaptable to many mounting points like poles, trees or walls.

Cons

• Not waterproof, so it will not keep areas dry in steady rain.
• Precise fit requires careful measurement because sizes are custom and may vary slightly by manual measurement.

Specifications

Brand	ShadeMart
Shape	Rectangle
Size	17 ft x 21 ft
Material	Woven HDPE (High Density Polyethylene)
UV Rating	Blocks up to 95% of UV rays
Mounting	Stainless steel D rings with heavy duty webbing
Water Resistance	Water permeable (not waterproof)

Our Verdict

The ShadeMart 17' x 21' rectangle shade sail is a practical, cost-effective way to add breathable sun protection to a patio, carport or boat cover. It pairs durable HDPE fabric and stainless steel D rings for reliable performance in sun and wind; choose it if you need strong UV protection and good airflow, but not a waterproof shelter.

Frequently Asked Questions

Is this shade sail waterproof?
The fabric is water permeable, so it allows water to pass through and is not intended as a waterproof cover.

Can it be mounted to trees or poles?
Yes, with the proper hardware kits it can be attached to poles, trees, walls or roofs using the stainless steel D rings.

Will it reduce temperature under the sail?
Yes, the woven HDPE fabric blocks most sunlight and can lower temperatures under the canopy by a noticeable amount.