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.

Your tool of choice ultimately comes down to personal preference. Many DIYers prefer applying stain with a lint-free rag, but others stick with a paint brush or a roller. Wipe the stain and work it into the wood, working with and against the grain. If you’re applying multiple coats, allow the stain to dry for around four hours between coats.

It’s necessary for paint to completely dry before exposure to rain, and that drying time varies by the type of paint used. Oil-based paint takes 6 to 8 hours to dry on average, meaning that’s the minimum time needed between the last brush stroke and the first raindrop. Latex paint dries faster at around 1 hour, and acrylic paint is even quicker, usually drying in about 30 minutes. If rain is in the forecast, check the paint manufacturer's details before laying on a new coat. 

In most cases, sanding an old deck before staining it is necessary to achieve a decent finish. If your old deck has a relatively new stain finish on it and you're only doing touch-ups, you can generally skip the sanding part. However, if your goal is to make the deck look and function better, sanding first is a must.