Image of smooth OSB boards but Can You Sand OSB to Smooth?

Can You Sand OSB to Smooth?

An oriented-strand board or OSB is an engineered wood material available in sheets like plywood. It features large wood chips or flakes sandwiched at various angles and makes an excellent choice for support materials, such as subfloors under a hardwood floor or new tiles. Also, OSB is easy to use. But woodworkers who want to know the correct preparation procedure for the board usually ask, Can You Sand OSB to Smooth?

Yes, you can sand OSB to smooth it. Light sanding helps level the surface and prevents splinters from scratching the material over the OSB. However, applying too much pressure during sanding may leave scratch marks on the surface. Therefore, please sand moderately.

On top of that, please note that you cannot sand the oriented-strand board to assume a particular shape. All you can do is make light passes with sandpaper to smooth out the surface. So, check out this article for more information about handling the material.

How Do I Make My OSB Board Smooth?

One way to make your OSB smooth is by using a resin filler coat and a putty knife. Also, apply the filler as thinly as possible and allow it to dry for about 20 to 30 minutes. Then, sand down the edges for a smooth result.

Here is a more detailed account of the smoothing procedure.

  • Set the oriented-strand board on a flat worktable or surface. This way, you’ll sand evenly over the entire surface.
  • Please have a dust mask and eye protection when sanding the board to avoid harm from sanding dust or splinters.
  • Lightly sand the board with a rough grit, ideally 60 and 80-grit. Also, you can consider using a rotary or oscillating tool featuring a sanding attachment, a sanding block, or a power sander for better coverage.
  • Wipe away sanding dust after using each grit to deliver a cleaner and smoother surface as you work. You can also blast the dust away with a can of compressed air or vacuum it with a soft brush attachment.  
  • Repeat sanding the OSB with medium grits between 80 and 120. The sanding will refine the surface as you work your way up the numbers. Even better, it will remove sharp edges and small splinters to deliver a smooth surface.
  • Proceed to more fine-grit sandpapers like 150 to 180. Here, you should run your hand over the board and feel only a smooth surface devoid of rough spots and splinters. 

Can You Sand and Stain OSB Board?

It is possible to sand and stain to an OSB surface. However, please do not expect a perfectly smooth board as you may not bring down the texture after staining the surface. Thus, only stain when you get the desired texture.

Remember that oriented-strand boards are similar to plywood and work best for subfloors to cover roofing and exterior wall studs. Therefore, most woodworkers do not stain or paint them. But this aspect does not mean you cannot stain OSB materials.

OSBs suitable for exterior and interior projects will accept paints, stains, and clear coat sealing products. In addition, although the boards are from tough, processed woods, they can rot with extreme exposure. So, here are some stain application tips.

  • Prepare the OSB

Believe it or not, oriented-strand boards are more vulnerable to water than other building and woodworking materials. Hence, please treat the board ends to keep the seal intact and prevent damage.

It is prudent to choose your suitable stain after confirming that the OSB undergoes moisture treatment. Moreover, various formulas deliver different results, and you need a product that suits your project needs. For example, gas-permeable varieties are the best as they highlight the wood strips and make them stand out.

On top of that, you may need to buy the factory sanded OSB for a smooth finish. But it is still possible to run the wire brush over the panels when customizing the boards. Also, please remove all the resin and loose wood particles and wipe the surface if you decide to DIY.

Make sure you lay the board on a pair of sawhorses. This move raises the working height and minimizes fatigue as you sand and stain the wood. In addition, get protective gloves and position a tarp under the OSB pieces. This way, you keep yourself and the workstation clean during the work.

Also, consider sanding the board with the palm sander and 100-grit sandpaper. Then, dust it off and sand again with 150-grit sandpaper. You can take some time to examine the surface to verify if you need a finer grit.

Lastly, remember that every consecutive sanding session gives a smoother surface for stain or polyurethane application. Therefore, feel free to sand the OSB once more with 220-grit sandpaper when the board is not flawless.

  • Apply the Stain

The formula pigments settle on the can’s bottom when it sits on the shelf for a long duration. Hence, mix it with a stir stick or a mixer on your drill before anything else. Then, dip your paintbrush into the solution and spread it on the wood. Also, please move consistently in one direction to get an even finish.

It would be best to apply thin, multiple layers than one thick coat. In addition, use the stain as evenly as you can to keep the surface from soaking it differently, leaving darker spots in some areas.

On top of that, use an all-purpose, three-inch paintbrush for the project. Then, allow the first coat to dry for about one hour to determine whether you want it darker. Also, check the manufacturer’s drying and curing times to facilitate the best outcome.

However, oil-based stains generally need more time to dry, and you may find yourself waiting for over eight hours. So, do not hurry to finish the work as it may lead to a worse result than an incomplete project.

  • Add a Finish

It is time to decide if you want the OSB to have a high shine or deliver a subtle gloss. However, the gloss level depends on your preference if you have a topcoat for wood and stain protection.

Dip a clean paintbrush into the chosen finish and spread it gently over the board’s surface. Then, brush the formula again in multiple thin layers. Here, ensure that you move in the same direction as before for a more consistent finish.

On top of that, keep an eye on the coats to avoid leaving brush marks and streaks. You can also facilitate a perfect finish by investing in high-quality application tools. For instance, a good brush will not leave bristles in your work.

Finally, let the finish dry well before sanding or adding subsequent coats. Also, it would be best to use 200-grit sandpaper to smooth the surface and lightly wipe off the sanding dust. Otherwise, you may compromise the topcoat with loose dust particles underneath.

  • Clean Up

Here, take time to clean your application equipment as the OSB surface dries. You can soak the paintbrushes in a paint thinner or mineral spirits to remove varnish, stain, or polyurethane. 

On top of that, consider using protective gloves during the cleaning process and discard the thinner properly after use. This way, you will minimize any health and environmental hazards.

How Do You Get Writing Off OSB?

You can remove writing off OSB by rubbing the surface with alcohol. Alternatively, dampen the corner of a rag with a fingernail polish remover and rub it against the writing several times.

Sandpaper is another accessory that would help remove writing off an OSB surface. However, you can only use it to even out the surface after wiping with rubbing alcohol or fingernail polish remover.

Below are simple tips on how to clear the board.

  • Rub or apply some ethanol or your preferred solution sparingly on the writing. Also, sometimes the ink may not dissolve immediately after application. Thus, wait for it to evaporate or try acetone instead.
  • Use a stiff brush to scrub the ethanol and clear as much ink as possible. 
  • Wash the board with a mild detergent and water and scrub again with a stiff brush. Unfortunately, OSB and similar materials absorb water readily, easily damaging the wood.

How Do You Fill Gaps in OSB Subfloor?

An effective way to fill gaps in an OSB subfloor is to use a patching compound. Mix the product to a stiff and mortar-like consistency, trowel it into the subfloor gaps, and wait for it to stiffen.

If trowelling does not deliver a perfectly smooth surface, you may need to sand the surface. Also, patching compounds have a daily short open duration for effortless spreading. Thus, mix as much as you can use in about 15 minutes and apply quickly. 

On top of that, ensure that you cover all the gaps during application as exposed OSB gaps may absorb water and crack. You can also use polyurethane subfloor caulk to bond the OSB sheets and keep the holes from widening.

Please note that leveling compounds are available in two primary formulations. We have cement-based formulations, like Henry 555 LevelPro, perfect for concrete and wood subfloors.

Alternatively, you can go for patching compounds, such as Fix-It-All. They consist of silica quartz and calcium carbonate and are only suitable for wood. Also, these patching products are better for spot filling as they are easier to mix to a stiff consistency. And better still, you can use them to fill larger gaps more than once.

It would be best to sand patching compounds to flatten overfilled holes and gaps. However, they may not deliver a perfect result when you have a larger area with higher spots and depressions. So, please consider a leveling compound for these projects.

Also, consider butt the subfloor sheets as closely as you can before fastening them. The strategy helps avoid gaps, guarantees moisture and thermal isolation, and protects the new flooring project.

Besides, you are better off filling knots when installing peel-and-stick tiles or sheet vinyl. This way, you will eliminate any roughness underneath the flooring and have a perfectly smooth surface.

That said, cement-based products and patching compounds harden within two hours and form a reliable seal against air circulation and moisture. Therefore, your OSB will still enjoy superior protection to your OSB, regardless of your choice.

How Do You Make OSB Look Like Drywall?

You can use the drip cap method, the roller strategy, or the knockdown technique to make OSB look like drywall. All these techniques have straightforward procedures and will deliver a suitable result.

But first, you need a few supplies before you start: Drop cloths, a paint roller pan, mud pan, electric drill, ribbon mixer, a paint roller handle with cover and extension pole, a putty knife, a crow’s foot stomp brush, five-gallon buckets of sheetrock mud or powder, a wide tapping knife, about ten inches, and a narrow taping knife.

Also, every style has its pros and cons, and it would be best to pick what works for you. So, let’s check them out separately.

The Roller Method

  • Cover the floor with drop cloths and put the mud in a bucket. Then, slowly add water and mix it with the ribbon mixer.
  • Continue with the process until you get the consistency of a milkshake.
  • Pour the watered-down mud into the roller pan. Next, roll the roller in the pan until you coat it with mud evenly.
  • Roll the mud into the wall and engage your creativity. Play with rollers with different naps and try pushing them with varying amounts of pressure or speed until you get your desired texture.
  • Start rolling the mud on the walls from a corner and work your way around the surface or room. You can add more designs to the surface by going back around the room a second time, adding rando, diagonal rolls.

The Knockdown Method

  • Put half the mud in a bucket and add water slowly. Then, mix the solution with the ribbon mixer until it is milkshake-thick. You may have to try out different consistencies before getting the best one.
  • Dip the crow’s foot brush into the mud solution and ensure that the mud coats the brush well for better coverage.
  • Push the crow’s brush onto the wall and drag it until no mud is left. Then, start in one corner and move around the room. Also, work with overlaps to cover the entire surface evenly.
  • Use the putty knife and the narrow taping knife to cover tight spaces around door frames and corners.
  • Drag the ten-inch taping knife at a forty-five-degree angle over the peaks in the mud to flatten them. Also, the mud should appear like the tops of the Rocky Mountains if you need a visual reference. 

The Drip Cap

  • Cover the walls with drop cloths to avoid accidental spills. Then, put half the mud in a bucket and add water slowly.
  • Add the ribbon mixer into the solution until it is thicker than a milkshake. Then, use a crow’s brush to apply the solution.
  • Consider using the putty knife or the narrow taping knife for tight spaces. This way, you’ll cover the whole area.

How Do You Treat OSB Board for Outdoor Use?

You can treat OSB for outdoor use by painting it with two coats of a premium exterior formula. Even better, this strategy protects the material from elements and enhances its life span.

On top of that, OSB is unsuitable as an exterior finishing material and may fail after extreme weather exposure. Therefore, you can only keep it safe from direct precipitation and sunlight by painting.

Below is a summary of the procedure.

  • You need a measuring tape, waterproof primer, circular saw, paintbrush or roller, a hammer, and stainless steel siding nails.
  • Measure the thickness of the board currently on your home’s exterior. Then, match the old material with the new one to prevent moisture damage.
  • Use a quality waterproofing primer to prime the OSB and the joints. Also, since most brands do not have a finish, it would be best to apply a primer. But you can forego this stage if you get an already painted board.

Moisture causes the board to expand in inclement weather, resulting in significant damage during thaw and freeze cycles. So, ensure that you use waterproof products.

  • Measure and cut the OSB to your preferred size. Fortunately, the board is available in four-by-eight or four-by-ten-foot sheets. Thus, you will always get suitable sheets to match your needs.
  • Align the OSB to keep it straight and square. Then, secure it firmly using stainless steel siding nails. Also, please note that stainless steel materials resist corrosion and thus are the best for this project.
  • Use nails strictly made from siding as they have a larger head to minimize pull-through issues. In addition, please space nails every 24 inches along the OSB’s sides, and utilize the studs behind the OSB to help you make the alignments or secure the boards.
  • Paint the OSB with two layers of premium exterior paint and consider a topcoat that can withstand the weather in your area.
  • Inspect the board often and repaint it when necessary to protect it from elements.

NB: Install the OSB at least six inches above the ground to minimize moisture issues from splashing water. And route rainwater through gutters away from the siding.

Frequently Asked Questions

  • Which Side of OSB Should I Paint?

It would be best to paint the OSB side with the sign “This side down,” as it is typically the smooth side. In addition, this writing helps roofers lay the smooth side down and have the rough side facing upwards.

Also, you may end up ice skating on the roof and hurt yourself if you put the smooth side up. Therefore, the manufacturers ensure that the board has a textured and smooth side for easy identification.

In addition, it would be best to prime the surface before painting to keep the OSB sap from bleeding through the surface. So, you will be better off when you work with the smoother side.

  • How Do I Hang My OSB Board Well?

Position the first panel vertically at one side of the wall and ensure that the long edge is flush with the corner framing. Also, ensure that the bottom edge flushes well with the sill plate’s base, which sits on the masonry foundation.

In addition, ensure that the OSB does not extend below the sill plate. Otherwise, moisture from the foundation can lead to swelling and delamination. You will also maintain a suitable nailing pattern by inserting one 8d nail every six inches.

Give the OSB panel about a ⅛-inch gap for expansion by tapping 16d nails into the stud beside the last panel. These nails also act as spacers and thus help you determine the best place to put the next board.

Store the boards in a watertight shed or garage before installation or even after purchase. The OSB’s edges get wet quickly and delaminate if you leave them unused for a long time. Therefore, it would be best to keep them dry and remove swollen edges before hanging.

Finally, please get the correct tools for the job. For example, you need a chalk line and tape measure to make accurate cuts. Also, a circular saw will come in handy when cutting through OSB.

Conclusion

Depending on your preference, oriented-strand boards are siding products available in laps or sheets. In addition, they come in multiple finishes that resemble stucco surfaces and various hardwoods. Therefore, you may prefer OSBs as an alternative to siding materials like vinyl or metal. But, there is a concern:

Can You Sand OSB to Smooth?

It is possible to sand OSB to smooth, but you cannot sand the surface into a specific shape. Also, too much pressure during sanding may leave minor scratches and an even surface. And thus, you are safer sanding the surface lightly.

On top of that, OSB is sensitive to extreme weather conditions. Hence, you will have to paint it for added protection, which requires light sanding to deliver a sophisticated finish.

Image of a woodworker wearing hearing protectors for woodworking

Tyron Otieno

Tyron is an avid woodworker and writer. He founded this website to help other woodworkers, whether hobbyists or professionals by sharing his knowledge and experiencie after a decade of woodworking.

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