If you are preparing your deck to be painted or refinished then you will need to get a sander. You might sand the deck by hand, but that is not a good idea. Putting aside the exhaustion and time it will take to sand by hand, the results will most likely be uneven. So, the best choice is to get a power sander.
What Type of Sander is Best for Deck?
There are several types of sanders to choose from, but the main choices come down to belt sander or floor sander. Selecting which one is right for the job will depend on different factors.
1. Belt Sander
The belt sander is the most traditional and probably the most familiar of all power sanding devices. It has the maximum material removal rate out of all the handheld power sanders. For most homeowners, with small and mid-sized decking a belt sander with coarse and fine sandpapers should do the job.
In case you are not familiar with this power tool, this tool has a belt of sandpaper that is spun between two drums much like the chain of a bicycle or a chainsaw. As the sandpaper moves, you press it against the surface which removes the top layer of the material. Balance is the most important factor to keep the results even.
A heavy-duty or professional belt sander will be needed to sand a large wooden structure such as a deck.
2. Floor Sander: Can You Use a Floor Sander on a Deck?
You can use a floor sander for finishing, although it will not be nearly as effective as a belt sander. This is because with a floor sander you have less overall control and cannot apply the pressure as evenly or effectively as a belt sander. Worse, if you do lose control it can gouge the deck and cause damage that will take a considerable effort to repair.
However, the main advantage of a flooring sander is faster material removal rate since it covers a larger area and has a heavy-duty motor. You can sand your deck with a floor sander if you go slow, stay steady, and ensure that all parts of the deck have been sanded evenly.
Other Types of Sanders
Random Orbital Sanders
Random Orbital sanders are also popular for sanding decks. This is a sander that uses a large, round surface that is spun by the motor. They are like floor sanders but are smaller with the disc or surface close to the hands for better control.
The one issue with orbital sanders is that they can create circular patterns in the wood unless you keep moving your sander. Belt sanders may also create marks, but they are not nearly as obvious and easier to redress in case you see such evidence. You can find a detailed comparison between the orbital sander and belt sander here.
Disc Sanders
Disc sanders can also be used, but they generally do not work if there is gunk present on the surface. If the deck has a buildup of gunk, a belt or floor sander can remove it rather easily, but a disc sander will have lots of issues.
Detail Sanders
Detail sanders are too small to sand the entire deck but are well-suited for sanding small areas that a belt or floor sander cannot reach. The same is true for file sanders which are great for sanding in tight places. The result is a clean surface that can be protected.
You could also use a drywall sander to do the job, but they are expensive compared to the belt and orbital sanders.
What to Look for in a Sander for Decking?
Once you have decided on the type or types of sanders, the next step is getting the right one for the job. The obvious factors include being of excellent quality and durability, making your investment one that can be used for years to come. If you do not plan on using a sander again for the foreseeable future, consider rending a professional version.
Weight
The weight of the sander needs to be heavy enough to press firmly against the deck, but light enough to comfortably move around. You should visit your local hardware store and pick up a sander or two to get a good idea of the weight.
Speed Settings
Variable speed setting is important because you will need to alternate in order to achieve the best results. Plus, adjusting the speed setting will help you better control the sander when you need to reach into corners or sides.
How to Sand a Deck for Refinishing?
There are different ways to sand a deck for refinishing, but what you want is the most effective in terms of results. The good news is that there are ways to sand the deck without wasting time or effort if you use the right equipment and approach. The first thing to do is schedule your sanding and refinishing for days where there will be no precipitation.
Step 1: Wash your deck
The first step is to clean the deck with a power washer. You’ll want to remove all the old gunk, dirt, and debris before you start sanding. Let the deck fully dry before you start sanding.
Step 2: Sand the main deck boards
Now, place the belt or floor sander on one side of the deck and work your way across. If you want to keep things simple, start with one plank and go all the way across, then start on the next plank and do the same.
What grit sandpaper for deck sanding?
For main deck boards or planks, use 60 or 80-grit sandpaper. This type of sandpaper is coarse enough to remove the old gloss while smoothing out the surface. Remember that you want the wood to be somewhat coarse to help the paint or finish to stick properly.
Step 3: Sand the handrails
Once you have completed the deck, start sanding the handrails with 80 to 100-grit sandpaper. You may want to switch to a smaller sander if the belt sander turns out to be too bulky. Be sure to inspect all areas that are going to be covered by the paint or finish before you proceed to the next step.
Step 4: Wash After Sanding
Start with a good broom and brush away the sawdust from the deck. You do not need to be thorough, but sweeping is fast and will save you time on the next step.
Plug-in and use the vacuum if you do not want to get the surface wet. A good vacuum will pick up all the sawdust from the deck. If you decide to wash the deck, plain water will do. Just remember to let it fully dry before taking the next step.
And that is how you sand a deck for refinishing. Once you are ready to apply the paint, stain, or finish, read the instructions and apply as directed.
Dan Miller is a professional toolmaker with extensive experience in the metalworking and tooling industry.
An avid DIY enthusiast and passionate hobbyist woodworker, Dan shares his expert knowledge here.