Many people know that they should sand their deck before refinishing it but may not know the best way to do this. Deep power washing or scrubbing with a brightener is essential when preparing an old wood deck for refinishing. However, this can cause wood fibers, 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. That's why sanding your deck wood is necessary before staining or sealing. Sanding your deck is an important step in preparing it for refinishing, but it can be difficult to do this evenly and thoroughly.
By following these steps when sanding your wood deck, you can ensure an even, smooth surface before refinishing:
Before You Begin
Follow whatever preparation steps recommended by the refinishing product you plan to use. In some cases, it may involve first using some chemical brightener on wood grayed with age or wood stained with dark tannins.
This treatment is followed by rinsing with clear water, then after the deck dries, the fuzzy wood fibers need to be removed by sanding. The power sanders used to sand a deck come in many forms. They range from standard household orbital sanders operated by hand to commercial upright rental sanders you can lease from home improvement centers and rental outlets.
Many homeowners find sand using an ordinary hand power sander, even though it requires patience, especially with a large deck that may need several days of work. Woods used on decks are typically softwood species. Belt sanders, whether handheld models or large uprights, tend to gouge softwoods, so an oscillating and random orbital sander is usually the better choice.
Make sure your deck is thoroughly dry before sanding it. If there has been recent rainfall or if you've power washed, wait for several days before sanding. Treat the deck surface, railings, and the edges of boards as different tasks, varying the sanding techniques for each.
Make sure you wear a particle mask and safety glasses while sanding while 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 doesn't 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.
Tools and Materials
- Scrub brush
- Breathing protection
- Detail sander
- Shop vacuum
- Knee pads
- Oscillating or random orbital sander
- Power washer
- Putty Knife
- Screw gun
- Wood filler
- Deck brightener
- Tack cloths
- Clean cloths
- Deck screws
Steps for Sanding a Deck
Wash the Wood
Wash the entire deck as directed by the stain or sealer manufacturer. If power washing, use a garden sprayer setting that doesn't damage the wood. Clean the wood deck with a deck cleaner or mild detergent. Make sure you find the best deck cleaners in the market that will be safe for this project. Use a bucket, hose, or power washer depending on the size of the job and power tools available.
Older decks may also require a stain or paint remover and anti-mildew treatment. Clean the exposed ends of the deck boards, and joist surfaces visible between the gaps. After cleaning, apply a wood brightener to restore wood luster and pH levels. Once the deck is clean, let it dry for 24 to 48 hours before sanding. Follow the directions on the cleaners and wear protective gear.
Inspect and Repair the Surfaces
Inspect the deck boards and surrounding area for problem areas such as rotted or damaged floor joists, loose nails and screws, protruding staples, and peeling paint. After filling any holes with epoxy wood filler, sand the repaired areas with fine-grit paper to prevent splinters and weak spots on the surface. If there are splinters or deep gouges in the wood, make sure they’re filled or repaired before you begin sanding.
Distress the Wood Decking Surface
Wear safety goggles, a breathing mask, and work gloves before you start distressing the wood the deck boards. Use an electric sander to sand down any raised nails or screws. Switch to medium grit paper to smooth out jagged edges created by the coarse sandpaper. Use a pole sander instead of hand-sanding with a regular sanding block for large areas.
Use an orbital sander for large areas to avoid creating visible sanding marks in the wood. Move the electric sander or pole sander back and forth across the surface of the deck boards, always keeping it perpendicular to the boards' grain lines. Lift on your wrists slightly to create a smoother sanded surface at the ends of the deck boards.
Sand the Edge Boards
Sand the edge boards that the deck boards will cover while you sand the deck boards to create a smooth transition between them. Rinse off all sawdust and dirt after finishing with each grit of sandpaper so you can get an accurate idea of how well you are doing until you get to your final finish.
When all surface scratches have been removed, rinse off the entire deck once more to remove all sanding dust.
Sand the Deck Rails
Railings are a visible part of the deck. Once it's clean and dry, fill in any cracks, holes, and scratches. Use an epoxy wood filler and a putty knife to apply and scrape off any excess. Once it's cured, sand the railings before sanding the deck. Use 20 to 80 grit for the vertical pieces and 100 grit where hands commonly touch.
Don't over sand, or the stain won't penetrate very well into the wood. Blow, wipe or vacuum off the dust and apply your pre-stain wood conditioner.
Vacuum the Entire Deck
Use a shop vac to vacuum the entire deck, then use tack cloths to wipe the surfaces free of any remaining clinging dust. Pay special attention to crevices and corners. Sweep any concrete or stone around the deck to avoid staining or discoloration of these areas. You will most likely have a leftover stain, so pour it into an unused paint tray and later use it for touch-ups.
Sand the Deck Floor with 80 Grit Sandpaper
Make sure the boards are dry before sanding and that the forecast for the next three or more days is for warm and dry weather. Use an orbital sander to sand the deck with 80 grit sandpaper. A belt sander can leave unsightly scratches on your floor, so it is not recommended for this process. Make sure you spread the 80 grit sanding dust around using a broom or leaf blower before you begin staining.
You'll also want to use a palm sander or oscillating sander, several sanding sponges, and sandpaper grits for edges and hard-to-reach areas. The deck size and condition impact the grit size and the necessary sanding. Rent an orbital floor sander to do large flat deck surfaces.
In addition to knee pads, dust masks, safety goggles, and ear protection, you'll also need a long-handled deck brush and paint stir stick, china marker, and plastic putty knife.
Begin by brushing off any dirt or large material with the deck brush. Wearing safety goggles, spread china marker ink over the entire deck surface to mark all of the areas that need to be sanded – this will allow you to see the areas you're sanding and avoid sanding areas that don't need it.
FAQs on Sanding a Wood Deck Before Refinishing
Should you clean the deck after sanding?
Once you've sanded your deck, you need to clean it to remove the wood dust from the pores and wood surface. One reason for sanding is to remove the raised wood fibers left from pressure washing the deck. So power washing will raise more fibers and require another sanding, plus more time to dry before pre-sanding.
Can you sand an old deck?
Yes. The biggest concern from the homeowner will be removing gray wood fibers from a pressure washed surface. But you can do this perfectly.
Can you use a belt sander on your deck?
Belt sanders are aggressive tools, especially when equipped with coarse sandpaper. Because they remove deck materials fast, they're suitable for larger surface areas and harder wood types. However, they can be hard and difficult to use in tight places.
Final Thought on How to Sand a Wood Deck Before Refinishing
Before cleaning, sanding a deck provides a clean, smooth, and absorbent surface for stain and paint to adhere to. It also makes it easier to remove paint that has bled through due to a thinner coat of sealer or stain while preventing discoloration from occurring in the wood.