Yes, it is generally a very good idea to seal your deck after pressure washing. Power washing removes not only dirt and debris but also a thin layer of wood, leaving the surface exposed and more susceptible to weathering. Sealing is almost always needed after this process. After a general cleaning, sealing isn't automatically necessary if the existing sealant is still intact. You can test the surface by placing a few drops of water on it. If the water beads up, the sealant is working. If it soaks into the wood, it's time to apply a new sealant. If it has been a few years, it's wise to remove the old sealant, wash the deck, and reseal for maximum protection.

Costs depend on coating type, labor, site preparation, and required finishes.

Stains penetrate wood best when it's cool and dry, so you want to avoid moisture. If the wood is wet upon application, or if it rains before the stain dries, the water will soak into the wood and displace the staining solution. This leads to a flaky and blotchy look, which is the opposite of a sumptuous even coat. Once the stain has fully cured, after about 3 days, rain shouldn’t cause you any problems.

It is not always necessary to remove old stain before restaining a deck. If the previous stain is in good condition and is compatible with the new stain, you may be able to apply a new coat after thorough cleaning. However, if the old stain is in bad condition, flaking, or peeling, it is best to remove it completely to ensure an even surface and proper adhesion for the new coat. Staining over a damaged layer can lead to an uneven finish and poor penetration. For best results, test a small area first and consult the stain manufacturer's guidelines.