How to Sand Your Wood Deck Before Refinishing

A deep power washing or scrubbing with a brightener/cleaner is an essential step when preparing an aged wood deck for refinishing, but this action causes the wood fibers of the decking, steps, and railings to swell and lift away from the wood as they expand with water. Once dry, these wood fibers can remain raised and may cause splinters. For this reason, light but thoroughly sanding your wood deck is a necessary step before staining or sealing. This crucial step will ensure that your refinishing job gives great results.

Before You Begin

Follow whatever preparation steps are recommended by the finishing product you plan to use. In some cases, this may involve first using some kind of chemical brightener/cleaner on wood that has grayed with age or wood that is stained with dark tannins. This treatment with a brightener/cleaner is usually followed by rinsing with clear water; after the deck dries, the fuzzy wood fibers need to be removed by sanding.

This treatment is most often recommended for aged cedar or redwood, and it may not be called for on pressure-treated pine lumber or with new cedar or redwood. On new wood, the manufacturer sometimes recommends a simple sanding, followed by immediate application of the stain or sealer.

The power sanders used to sand a deck comes in many forms, from standard household orbital sanders operated by hand to commercial upright rental sanders you can lease from home improvement centers and rental outlets. Any of these will adequately sand your deck if used properly. Most homeowners find it entirely possible to sand using an ordinary hand power sander, though patience is required, especially with a large deck that may need several days of work.

Remember that woods used on decks are typically soft-wood species. Belt sanders, whether hand-held models or large uprights, tend to gouge softwoods, so an oscillating or random orbit sander is usually the better choice.

Make sure your deck is thoroughly dry before you sand. If there has been recent rainfall or if you have power washed, wait several days before sanding. Treat the deck surface, the railings, and the edges of boards as different tasks, varying the sanding techniques for each. 

Safety Considerations

Make sure to wear a particle mask and safety glasses while sanding, as wood dust poses health risks if you breathe it. Knee pads and hearing protectors will also make your job safer and more comfortable. Short-term exposure to wood dust probably does not create the risk of cancer faced by industry workers, but even short-term exposure can cause an allergic response or respiratory reaction, such as an asthma attack. The risk of reaction is especially pronounced with dust from red cedar.