How to Sand a Wood Deck before Refinishing

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When preparing an old wood deck for refinishing it, it is important to do a deep power wash or scrub with a cleaner/brightener. However, this causes the wood fibers of the steps and decking to swell and lift off the wood as they expand with the water. These wood fibers may remain raised after drying, which can lead to splinters. Before sealing or staining, it is important to lightly but thoroughly sand your wood deck. This is a crucial step that will make sure your refinishing job yields great results.

Before You Begin

Follow the instructions of the product you intend to use for preparation. This may include first applying a chemical cleaner/brightener to wood that has become gray with age or stained with dark tannins. After using a brightener/cleaner, rinse the deck with clean water. The fuzzy wood fibers can then be removed by sanding.

This is a recommended treatment for old cedar and redwood. It may not be necessary for pressure-treated pine lumber, or for new cedar or redwood. Manufacturers may recommend sanding new wood and then applying the stain or sealer immediately.

There are many types of power sanders that can be used to sand decks. These range from household orbital sanders that can be operated manually to larger, commercial-grade rental sanders that you can rent from rental shops or home improvement centers. If used correctly, any of these sanders will be able to adequately sand your deck. It is easy to sand a deck with an ordinary hand power sander. However, patience is necessary, especially if you have a large deck that will require several days of work.

Woods used for decks are usually soft-wood species. Hand-held or large-sized belt sanders can gouge softwoods. An oscillating or random orbit model is better.

Before you sand your deck, make sure it is completely dry. Wait several days if there have been recent rains or if your deck has been power washed. You can treat the deck surface, railings and edges of the boards as distinct tasks by using different sanding techniques.

Safety considerations

While sanding, make sure you wear safety glasses and a particle mask. Wood dust can pose health risks if it is inhaled. Your job will be safer and easier if you have hearing protections and knee pads. Although wood dust is not likely to cause cancer, short-term exposure may increase the risk for workers in the industry. However, even short-term exposure could trigger an allergic reaction or respiratory reaction such as asthma attacks. Red cedar dust is particularly susceptible to allergic reactions.

What you’ll need

Equipment / Tools

  • If necessary, a potty knife
  • If necessary, power washer
  • Scrub brush
  • Bucket
  • Screwgun (if needed)
  • Protection for your breathing
  • Eye protection
  • Optional: Knee pads
  • Random-orbit or oscillating sander
  • Detail sander (if needed)
  • Shop vacuum

Materials

  • Deck brightener (if needed)
  • Wood filler (if neeed)
  • Deck screws (if necessary)
  • Sandpaper (60- and 80-grit)
  • Use clean cloths
  • Tack cloths

Instructions

Get rid of the wood

The manufacturer of the stain or sealer will instruct you to wash the whole deck. Power washing should be done with a setting that does not damage the wood. To remove any traces of brightener/cleaner or chemicals from the cleaner, thoroughly rinse the deck.

Tip

Use a chemical cleaner to clean landscape plants around your deck. Oxalic acid and other compounds can cause severe damage to living plants.

Inspect the surfaces and repair them

Begin by inspecting the surfaces that you plan to sand, including decking, railings, edges, stairs and stairs. All fasteners should be driven to the wood’s surface. Old screws might need to be replaced. You should remove any boards that are loose and drive new fasteners.

Make sure you have filled any splinters or gouges in wood before you start sanding. Wood fillers should be fully dried and hardened before you start sanding.

Sand the Decking Surface

Use a power sander to attach 60-80 grit sandpaper. You don’t want to achieve the smoothest surface possible. Avoid finer-grit sandpapers as they can clog pores and prevent sealers and stains from reaching the wood.

Use medium pressure to sand all areas of the decking. As you go, check for uniformity of appearance. Do not sand the surface to a smooth finish. Pressure-treated pine, cedar, and redwood are all relatively soft woods and can be damaged or gouged if you use too much pressure.

This same technique can be used to sand the top of the stair treads.

After you are done, vacuum thoroughly the deck and stair treads using a shop vacuum.

Sand the Board Edges

Sanding the edges of the deck boards can be difficult, especially if there is a low bottom baluster rail making it difficult to reach. Here, a smaller detail sander may prove useful if your standard orbital sander won’t fit. Use a sandpaper grade of 60-80 for the decking boards’ end grain. Sanding unevenly can cause stains to be absorbed unevenly.

Clean the edges of the boards and then wipe them clean.

Sand the Railings

Sanding your deck’s railing is important as it is the most visible and where people will focus their attention. To avoid any injuries to your hands, smoothen the handrail.

Use 80-100 grit sandpaper for railings. Make sure to get into all crevices and surfaces. You may need to use a detail sander, or even sand by hand to reach all areas. However, don’t sand too smooth to prevent staining.

Clean the railings well.

Vacuum the entire deck

You can vacuum the deck with a shop vacuum once more. Then, use tackcloths to clean the surfaces of any clinging dust. Be sure to pay attention to corners and crevices.

Now your deck is ready for sealing/staining. This should be done immediately after you have sanded the deck to prevent it from weathering or getting dirty. You can wait to finish sanding, but you should vacuum the deck and wipe it down again with tackcloths before applying sealer or stain.

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