Deck Doctor — How Do I Refinish A Deck — Answer 9

Deck Sanding — An Essential Step

Proper preparation includes deck sanding. The sanding can be minimal, reducing any fuzz left after washing, or extensive, providing a truly smooth surface ready for staining.

It is possible to power wash a deck, allow to dry then apply the stain, but a wood deck is designed to be walked on, played on and leaned on.

The amount of deck sanding you do will depend on the old finish and the desired look you want. Most old deck stains will be removed with the pressure washer and cleaning chemicals.

Paint, varnish and solid color deck stains will have to receive a vigorous and labor intensive sanding in order to be fully removed. If you plan on repainting, a full sanding isn’t necessary. Simply remove all loose finish and sand the edges smooth.

Tool List for Sanding Wood Decks

* Hammer or screw gun to sink any nails or screws that have become loose.

* Hand scraper for tight areas or peeling thick finishes. The same type of scraper you would use while preparing your house for painting. Use sharp blades or have the scraper sharpened.

* Belt sander for the tops of handrails. Can also be used on the floor, but is more difficult than other types of sanders.

* Disc sander or large angle grinder with either course buffing pads or sanding disks. The Makita GV5000 disk sander uses a 5-inch disc and a large angle grinder uses 8-inch discs. Crowder Painting uses both types when sanding wood decks.

* Finishing sanders such as palm or vibratory sanders can also be used. These will be the most trouble free but the most labor and time intensive. I use finishing sanders after an initial hard sanding with the angle grinder if a smoother finish is desired.

* Leaf blower to remove the dust left after deck sanding. The dust can also be washed away using a pressure washer and low pressure, 1200-1500 psi. Washing with plain cold water is the best as the house siding can also be rinsed plus this will help open the wood pores often clogged with dust after sanding. Remember low pressure, this is a rinsing only not an actual cleaning.

The type of sanders you use will depend on your skill level plus the desired look and feel. Use a sander you are comfortable operating. Remember redwood, cedar and treated lumber are soft and will sand easily when compared to hardwoods.

Using a floor edger on a T&G porch floor. Other options are floor sanders, available at rental outlets. These include the drum sander, edger and very large vibratory sanders. All of these options are primarily used to sand flat hardwood floors and not wood decks.

Deck floors have a tendency to warp and cup, making them difficult to sand with this equipment.

* The drum sander can do considerable damage is the wrong hands. Should only be used by skilled hardwood floor finishers.

* Floor edgers can be used for some deck sanding, but will have a difficult time on the uneven terrain of most deck floors. I have used these sanders on porches with a T&G wood floor, but not on redwood or cedar decks. These sanders use a large sanding disc, same as the angle grinder.

* Very large vibratory sanders weigh 100 pounds or more and use either a large sanding or buffing pad. Looks like a very large vibrating orbital finishing sander. Although easy to use they are not suitable for badly warped floors.

All of these sanders can be used while deck sanding, but should be confined to deck floors without severe warping. The best woods for floor sanders are the premium hardwoods that are not prone to severe warping.

Deck Sanding Steps

The process involved while sanding wood decks is quite simple and straightforward. The end result is worth the extra effort. Any combination of these steps can be used depending on the condition of the deck surfaces and the remaining finish.

Reset Loose Nails or Screws

Although it’s obvious to hammer in loose nails there are a few guidelines that need to be followed. Plus now is the time to consider an option.

Do not create a dent with the hammer. The nail needs to be below the surface, but a hammer alone will leave a dent that will show after staining. Instead use a nail set or another large nail to force the nail below the surface while hammering.

An option is to pull the loose nails and replace with long deck screws. Nails always come loose while a screw bites and holds the wood. While pulling nails use a scrap piece of thin wood, 1×2 or plywood, under the hammer to prevent denting the wood. A longer screw than the nail is needed in order to bite into new wood and not become loose. Choose a screw 1-inch longer if possible.

When you think you are done slowly walk across the floor and check for loose boards. Also check the handrails for loose boards and make sure it is sturdy and sound.

Perform all Repairs

All repairs need to be accomplished before you start any deck sanding. The new wood can be blended with the old to a degree with sanding. Any questionable wood should be replaced. Pay special attention to the frame and floor joist. Rot always starts here. An option for deck floors is to flip over the floorboards before starting the deck sanding. I have done this on a few decks over the years.

You might be amazed how good the other side looks. This works best with parallel floors; angle cut boards cannot be flipped so easily.

Remove the nails or screws from a few boards at a time. The boards can be numbered on the current face to keep things organized. Now is a great time to seal the old face and edges of the floorboards with stain before flipping.

While the boards are removed inspect the joist for rot. If in good shape cover the edge of the joist with strips of rubberized roofing membrane available at your local home improvement center. The joist are 1Ѕ inches wide, use strips 2-inches wide. This will provide full protection to this edge and prevent future rot from taking place.

Deck Sanding Ideas

Before grabbing the sander and getting to work think about the condition of the wood, the amount of deck sanding needed and the grit of the sandpaper or sanding disks.

Using a finishing sander on a wood deck floor. Peeling paint or very ruff wood requires the most work. Start your deck sanding with 36 grit, to quickly remove the peeling paint or ruff wood, or 60 grit if the wood is in better shape. Be careful, this coarse grit can remove a lot of wood very fast depending on the type of sander you are using.

At this point the surface will be relatively smooth and flat. You could stop here and stain or continue sanding with a finer grit.

A finer grit at this point could be 80 or 120. Very smooth surfaces are normally reserved for the handrails or sitting areas. The floor doesn’t have to be super smooth, but all splinters and any very ruff areas need to be reduced then blended with the rest of the deck.

Using a finishing sander on Brazilian Mahogany handrail. Soft woods, such as redwood and cedar, can be sanded with finer grits. Exotic hardwoods require 60-80 grit sand paper to start. The type of wood, condition and any remaining finish will dictate the right grit and type of sander.

Often wood deck sanding requires more than a simple sanding. Perform any necessary repairs and use common sense.

Now that the sanding is finished give the deck a good rinsing with a power washer to remove the dust and open up the woods pores. Allow to dry before applying the deck stain.


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