During a renovation, I once attempted to sand an entire living room with a grit that was too coarse based on a client’s insistence that "it’ll be faster." Unfortunately, this decision led us to spend the following weekend re-sanding. This experience taught me to treat grit numbers with significant respect, similar to how one would heed traffic signals; using the incorrect grit can lead to damage or wasted time. When getting walls ready for painting, selecting the appropriate sandpaper grit serves as an effective measure to prevent future repainting troubles. This decision is also interconnected with broader aspects such as room layout and surface planning. I often recommend using tools like Homestyler for space planning inspiration, which helps visualize the entire room before any paint application occurs.
1. New drywall or skim coat: start with 120–150 grit
For newly installed drywall or a fresh skim coat, my first choice generally lies in the range of 120–150 grit. This grit level effectively smooths out high points and joints without damaging the paper surface. It’s sufficiently aggressive to level seams while remaining fine enough to prevent noticeable scratches. To achieve an exceptionally smooth finish, a subsequent lighter pass of 180–220 is advisable. Do bear in mind, the trade-off includes dust accumulation; wearing masks and using a vacuum-backed sanding block simplifies the cleanup.
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2. Plaster and repaired areas: 150–220 grit
Plaster can be quite unpredictable, so I typically approach patched or repaired sections with a grit of 150–220, depending on the hardness of the patch. Initially, begin with a coarser grit for uneven areas, and then feather with 220 grit to ensure the repaired section smoothly blends into the surrounding plaster. This minor additional step helps avert shadows and visible differences after the paint has dried.
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3. Removing old paint or leveling rough surfaces: 80–100 grit
When it comes to stripping old, flaking paint or leveling very rough surfaces, an 80–100 grit is ideal for the heavy-duty work. While it’s effective, this grit can also leave noticeable scratches, so it’s wise to follow up with 120–150 grit and finish with 180–220 before painting. For those on a budget, I occasionally use a free floor sketch tool to identify problem areas and devise a work plan — this approach helps prevent over-sanding one wall while overlooking another.
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4. Between coats and deglossing: 220–320 grit
When sanding between paint layers or dulling a glossy finish before applying another coat, I often rely on 220–320 grit. This range effectively eliminates minor imperfections while creating enough texture for the subsequent layer without compromising the existing paint. The benefit lies in achieving a smooth, professional result, although it should be noted that this grit won’t handle heavy defects — coarser grits will be necessary first.
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5. Trim, doors and high-sheen finishes: 320–600+ grit
For sanding wood trim, doors, or high-gloss finishes, I transition to 320–600 grit for final smoothing and wet-sanding during topcoat applications. This creates a luxurious finish that enhances the appearance of trims, although it does take a bit longer. It’s essential to apply light pressure and ensure the surface is thoroughly cleaned before painting. In kitchens or bathrooms, where moisture and sheen are considerations, I frequently direct clients to practical kitchen layout references, helping to coordinate trim work with fixtures and finishes — this minimizes the need for awkward touch-ups down the line.
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FAQ
Q1: What grit sandpaper should I start with on painted walls?
A1: If you need to remove old, flaking paint, start with 80–120 grit. Otherwise, select 120–150 grit for general smoothing, followed by a fine 180–220 grit before priming.
Q2: Is a higher grit always better for a smoother finish?
A2: Although higher grit results in a smoother texture, it’s less effective at material removal. Thus, using a sequence from coarse to fine is the best strategy to achieve both leveling and smoothness.
Q3: How can I prevent swirl marks from sanding?
A3: Utilizing a sanding block or sponge ensures consistent pressure, sanding with the grain of the material where possible, and finishing with finer grits (like 220–320) to erase visible scratches.
Q4: Is it possible to wet sand walls between coats?
A4: Wet sanding is generally reserved for high-gloss surfaces and trim rather than expansive wall areas. For walls, opting for dry sanding along with effective dust control tends to be more practical.
Q5: Do I always need to apply primer after sanding?
A5: Yes — sanding opens up the surface, and a primer seals it, aiding adhesion and ensuring a uniform look for the topcoat.
Q6: What safety gear should I wear while sanding?
A6: At a minimum, you should wear an N95 mask, eye protection, and utilize dust extraction or a vacuum attachment to minimize airborne dust particles.
Q7: Where can I find official guidance on sanding and surface preparation?
A7: Detailed preparation and sanding guidelines can be obtained from paint manufacturers such as Sherwin-Williams; check their technical resources for product-specific advice (Source: https://www.sherwin-williams.com).
Q8: How do I decide between different sanding tools (hand block, pole sander, orbital)?
A8: Hand blocks offer greater control for minor repairs, pole sanders are efficient for high ceilings and walls, and orbital sanders offer speed but can risk over-sanding if not used carefully; choose based on the size of the area and your comfort level.
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