It is definitely worth sanding a deck to ensure the wood absorbs new stain. Sanding a deck removes the outer layers of aging wood, allowing the stain to penetrate. It also gives a fresh look to the entire surface as part of the deck refinishing process. Without sanding, your stain or sealant is less likely to absorb into the wood. While sanding a deck is a time-intensive project, the rewards are noticeable and long-lasting.

Ultimately, overapplication of stain can compromise the deck's appearance, durability, and longevity. It may result in an uneven finish, with excess stain pooling, dripping, or drying into thick patches. It can also obscure the wood's natural grain and texture, detracting from the desired aesthetic. Moreover, excessive staining may not fully penetrate the wood, leading to poor adhesion and premature wear. Additionally, thick layers of stain are prone to peeling, cracking, and blistering as they struggle to bond with the surface. 

Generally, a patio is more accessible than a standard deck because patios are constructed at ground level. However, decks can be made accessible by adding a wheelchair-accessible ramp, a vertical lift, or a stair lift along the entry. An ADA-compliant deck ramp costs about $3,000 on average. The additional investment will provide a much friendlier experience for your guests with movement impairments.

Pressure-treated wood contains preservatives that give the material internal protection from rot and pests. Untreated lumber won’t last more than a few years unless you choose a more expensive wood, like cedar, that naturally stands up well to moisture. Composite decking can outlast wood but is more expensive and doesn’t look as natural. Keep in mind that you’ll need to seal any exterior wood product to protect it from the elements and other forms of external damage.