Sanding a Wood Deck
After a deep power washing, the wood fibers of the various components of the deck often raise as they expand with water. Once dry, these wood fibers can often remain raised and may cause splinters. For this reason, you should plan on sanding your wood deck after power washing and before staining and sealing. This crucial step will ensure that your refinishing job gives great results.
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 ordinary consumer power sanders, though patience is required, especially with a large deck that may need several days of work if you are using a hand power sander.
Remember that woods used on decks are typically soft-wood species that can be gouged if you use power tools or sandpapers with a very rough grit. Belt sanders, whether hand-held models or large uprights tend to gouge softwoods, so oscillating or orbital sanders often do a better job. Also, 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.
Make sure your deck is thoroughly dry before you sand. If there has been recent rainfall or if you have power washed, wait a several days before sanding. Treat the deck surface, the railings, and the edges of boards as different tasks, varying the sanding techniques for each.
Start by carefully inspecting all the surfaces you will sand—surface decking, edges, stairs, and railings. Make sure all fasteners are driven down below the surface of the wood. Some very old screws may need to be removed and replaced. If there are any loose boards, now is the time to drive new fasteners to secure them.
If there are splinters or deep gouges in the wood make sure these are filled or repaired before you begin sanding. If using wood fillers, make sure they are fully dry and hardened before you move on to sanding.
Sanding the Deck Surface
When sanding hardwoods, the goal is usually the smoothest surface possible, but this is not the case when sanding an exterior deck surface. For sanding deck floorboards, use sandpapers with grits no rougher than 60 or 80. Sanding with finer-grit papers (100-grit or above) will smooth the wood to the point where the pores begin to close down, which will hinder the absorption of stain or sealer into the wood. Use medium pressure on your hand sander, checking for evenness of appearance as you go.
Thorough vacuuming of all surfaces is important before you move on to staining and sealing the deck.
Sanding Board Edges
Sanding the outer edges of the deck board may be a little difficult depending on your deck design, especially if the railings have a very low bottom baluster rail that makes access difficult. Here, a smaller detail sander may prove useful if your standard orbital sander won't fit. Again, use a sandpaper grit of 60 to 80 for the end grain of decking boards, and make sure to sand as evenly as possible, since stains are often absorbed unevenly into end grain if the boards aren't sanded to uniform evenness.
Again, wipe end grains free of dust before moving on to staining and sealing.
Sanding the Railings
Sanding the railing of your deck is very important since it the most visible element, and the one where people focus their attention. Additionally, the handrail is particularly important to get smooth to avoid splinters that might injure hands.
On railings, use 80- to 100-grit sandpaper, and take pains to sand all surfaces and crevices. Here, a detail sander or even sanding by hand may be necessary to get to all areas, but again, do not sand to a smoothness that will prevent the stain from penetrating.
Vacuum thoroughly, but also wipe all surfaces with a clean rag to remove all trace of sanding dust before you move on to staining and sealing.
Clean the Wood Before Staining or Sealing
It is best to move only staining and sealing very quickly after sanding. Make sure that all surfaces are carefully vacuumed free of sanding dust, then wipe the surfaces down with a tack cloth to remove all traces of dust before moving on to staining or sealing.