Limewash and whitewash are two techniques used to give brick a light, matte finish, but they differ in composition, application, and permanence. The best choice depends on your aesthetic goals and the specific surface.

Composition

• Limewash: A natural and environmentally friendly option made from limestone, water, and sometimes pigments. It is breathable and soaks into porous surfaces like brick.

• Whitewash: Traditionally made from lime, water, chalk, and binders, but a similar look can be achieved with watered-down white paint. It is paint-based and sits on top of the surface.

Appearance and Finish

• Limewash: Provides a natural, textured appearance that allows the brick's character to show through. It offers a more traditional finish.

• Whitewash: Creates a softer, more opaque finish, often used for a rustic or shabby-chic style.

Application and Permanence

• Limewash: Is semi-permanent and can be removed, making it a good choice if you might want to change the look in the future. It requires more skill to apply and cannot be used on previously painted brick.

• Whitewash: Is a more permanent solution. It is more forgiving to apply and can be used on painted brick. However, because it sits on the surface, it can trap moisture.

Ultimately, if you want a breathable, natural, and reversible finish for unpainted brick, limewash is a great option. If you need a more permanent, opaque coating that can be applied over painted surfaces, whitewash is the better choice. Whitewashing may also be more economical, costing approximately $1.40 to $4.20 per square foot.

Whether you can paint over your existing paint depends on what’s on there. Most of the time, you’ll want to sand down or scrape off the paint that’s currently coating your surface. Epoxy paint, for example, won’t let new paint stick to the surface. Latex paint is more forgiving and will accept a new coat, but a primer is recommended if you’re switching colors.

There are deck restoration products and oil-based wood stains that can help bring back some of the color and shine to your faded Trex decking. However, if your boards are suffering from serious fading due to UV rays or chemical cleaning products, don’t expect miracles. Also, these products are only suitable for use on the older Trex boards, not the capped, second-generation Trex products. 

For the longest-lasting exterior paint, consider acrylic or enamel (oil-based) paints. Acrylic paints, including acrylic latex and acrylic enamel, are known for withstanding harsh weather and sun exposure. Enamel-based paints are also one of the most durable options available. While latex paint is common, it typically has a shorter lifespan than acrylic or oil-based options. The paint's finish also affects its durability; a higher gloss finish is generally more durable. For resistance to moisture and cracking, matte and satin finishes can be effective, while a high-gloss acrylic or oil-based paint offers a combination of maximum longevity and durability.