When it comes to drywall finishing, sanding is one of the most critical steps in achieving a smooth, flawless surface. Whether you’re preparing drywall for paint or trying to eliminate imperfections from a joint compound, choosing the right grit sandpaper can make a huge difference in the final result. This guide will cover the various types of sandpaper grits available and the best uses for each to help you achieve the smoothest finish possible on your drywall.
Why Sand Drywall?
Before diving into the specifics of sandpaper grit, it’s important to understand why sanding drywall is necessary. Drywall sanding serves multiple purposes:
- Smooth Out Joint Compound: After applying joint compound (also known as mud), you may notice visible ridges or uneven areas. Sanding removes these imperfections, leaving behind a smooth and seamless surface.
- Blend Seams: The seams where drywall sheets meet can be slightly raised or uneven. Sanding helps blend the joint compound with the surrounding drywall for a uniform finish.
- Prepare for Painting: A smooth, even surface is essential for a successful paint job. Sanding ensures that the drywall is prepped for painting and that the paint adheres properly.
- Remove Dust and Debris: Sanding helps remove dust, debris, and any excess compound that has dried unevenly.
Different Grits of Sandpaper
Sandpaper grits are categorized by the coarseness or fineness of the abrasive particles attached to the paper. The grit number indicates the number of abrasive particles per square inch—lower numbers represent coarser abrasives, while higher numbers indicate finer abrasives. Understanding the role of each grit level will help you select the right one for your drywall sanding needs.
1. Coarse Grit Sandpaper (40–60 Grit)
Coarse grit sandpapers, such as 40 or 60 grit, are typically used for heavy-duty sanding tasks. These grits are too rough for drywall finishing, as they can leave deep scratches and gouges in the surface. However, they are occasionally used during the initial stages of sanding when you need to remove large amounts of material or level uneven surfaces.
These grits can be useful if you’re repairing extensive drywall damage or if you need to take off a lot of joint compound. But for general drywall finishing, using coarse grit sandpaper should be avoided unless absolutely necessary.
2. Medium Grit Sandpaper (80–100 Grit)
Medium grit sandpaper, usually between 80 and 100 grit, is typically used after the rough sanding is complete and when you need to smooth out imperfections left by the coarse sandpaper. It helps to refine the surface and prepare it for finer sanding.
For drywall, 80 grit is commonly used to lightly sand the joint compound once it has dried. It works well for knocking down any high spots or ridges that might have been left behind during the taping and mudding process.
Medium grit sandpaper is often the go-to choice for most drywall sanding applications, as it strikes a balance between abrasiveness and smoothness. It can remove material without being too aggressive, making it ideal for smoothing compound applications without leaving scratches.
3. Fine Grit Sandpaper (120–150 Grit)
Fine grit sandpaper, such as 120 or 150 grit, is perfect for achieving a smooth finish on drywall. After using medium grit sandpaper, you can follow up with fine grit to further smooth out any rough patches and create an even, seamless surface. This step is crucial in preparing the drywall for painting.
Fine grit is ideal for sanding the final layers of joint compound to achieve a smooth finish, especially if you are working with a light coating of compound. This grit is gentle enough to smooth out the surface without removing too much material.
4. Very Fine Grit Sandpaper (180–220 Grit)
For ultra-smooth finishes, very fine grit sandpapers like 180 or 220 grit are the best choice. These are often used for final sanding before painting, especially if you want to achieve a near-perfect, flawless surface. This grit level is ideal for lightly buffing the surface to remove the last traces of imperfections, including minor bumps and scratches.
Although very fine grit sandpaper is great for smoothing the surface, it’s important to use it sparingly to avoid removing too much of the compound and potentially ruining the finish. After applying the last coat of joint compound, you can use 180 or 220 grit to lightly sand the drywall for a glass-like finish.
5. Extra Fine Grit Sandpaper (240–400 Grit)
Extra fine sandpaper is rarely used for drywall applications, but it may come in handy in very specific situations where an ultra-fine finish is required. This level of grit is typically reserved for polishing surfaces, such as wood or metal, rather than drywall. However, in some instances, such as when preparing drywall for a high-quality finish or for use with specialty coatings, you might consider using 240 or 400 grit sandpaper.
Choosing the Right Sandpaper Grit for Drywall
When deciding which grit to use for drywall sanding, consider the following factors:
- Stage of the Drywall Process:
- For rough sanding after the first or second coat of joint compound, start with 80–100 grit sandpaper.
- For final smoothing, 120–150 grit sandpaper should be used.
- For the smoothest finish before painting, 180–220 grit sandpaper is ideal.
- Type of Drywall Joint Compound:
Some joint compounds are thicker or dryer than others, requiring different sanding techniques. For thicker compounds, a coarser grit may be required for initial sanding.
- Desired Finish:
If you’re looking for a perfectly smooth finish, you’ll want to use finer grits like 150, 180, or even 220 grit for the final stage.
- Sanding Tools:
If you are using a sanding block, you can control the pressure and achieve more consistent results. However, for larger surfaces, a pole sander or a drywall sanding machine might be necessary for efficiency.
- Dust Control:
Drywall sanding can create a lot of dust. If you’re working in an enclosed space, be sure to use dust extraction systems or wear a proper dust mask. Some sandpaper options come with dust-free features, which might make sanding easier and cleaner.
Tips for Sanding Drywall
- Don’t Over-Sand:
Be cautious not to sand too aggressively, especially when using medium or fine grits. Over-sanding can damage the surface, especially if you’re sanding through joint compound and into the drywall itself.
- Use Circular Motions:
When sanding, use a circular or back-and-forth motion to avoid creating visible lines or patterns on the surface.
- Sand Between Coats:
Sanding between each coat of joint compound helps achieve a smooth finish. After each coat has dried, lightly sand it with the appropriate grit, then apply another coat of compound if necessary.
- Clean the Surface After Sanding:
Always wipe down the surface after sanding to remove any dust and debris before applying paint or additional coats of joint compound.
Conclusion
The right grit sandpaper is essential for achieving a smooth, flawless drywall surface. Coarse grits are used for heavy sanding and leveling, while medium grits are ideal for smoothing out the majority of imperfections. Fine and very fine grits are reserved for finishing, with 180–220 grit being ideal for a polished look before painting. Always work in stages, gradually moving to finer grits to avoid damaging the surface, and remember to clean the surface after sanding to prepare it for the next step in your project.
By selecting the right sandpaper grit for each stage of drywall sanding, you can ensure that your walls are perfectly prepped and ready for the next phase, whether it’s painting, wallpapering, or simply leaving the surface as-is. Happy sanding!