Skimming The Surface: Mastering The Art Of Drywall Skim Coating

Skim coating is a great way to smooth out or prepare worn or damaged walls for a touchup. It is a relatively easy task that even novice drywall workers can add to their arsenal. Skim coating is also known as a level-five drywall finish. It is the process of smoothing over worn or damaged drywall with a thin coat of diluted joint compound to improve the look of the surface. It is usually done to repair damage and improve the appearance of the wall. It can also be applied in the form of either a single layer to touch up a small area or multiple layers to provide a smooth surface. Once the skim coat is applied, the surface is then often painted or retextured.

Prep the walls

Before you start skim coating, you need to prepare the walls. First, cover up any areas that will not be skim-coated. Then, turn off the electrical circuits to outlets and light switches. Remove the faceplates and cover the outlets or light switches with painter's tape. Lay down drop cloths and tape them up to the wall baseboard.

Next, you'll want to prime the wall. Priming will seal any loose paper on the drywall. Apply one to two thin coats of an appropriate primer and wait for it to dry thoroughly before beginning to skim. A fast-drying, stain-sealing drywall primer will do the trick.

If there are any holes, torn-away paper, or uneven sections, patch these problems with a setting-type joint compound. Let the compound harden before you start skim coating.

Choose the right joint compound

For skim coating, you'll want to use a lightweight, all-purpose joint compound. This type of compound serves almost no structural purpose, so a heavy-body compound is not necessary. Lightweight compound is also easier to sand smooth.

Mix the joint compound

Mix the joint compound in a bucket according to the mix ratio on the product instructions. It's often better to use slightly less water than the instructions call for to produce a heavier, stickier product. This will give the skim coat greater strength and make it cleaner to apply. Mix to a stiff, yogurt-like consistency.

First, put slightly less water than needed in a mixing container or bucket. Then, add the compound to the water and mix. After mixing, add the remaining water if needed. Adding the compound to the water will help you achieve a lump-free mixture.

Apply the joint compound

Now it's time to apply the joint compound to the wall. Use a paint roller to roll out a section about 2 feet wide by 8 feet high. Press the roller firmly into the wall to force out any bubbles. It's best to work in smaller zones so that the compound doesn't dry up on you.

Make sure to keep the compound consistent across the surface. Inconsistent compound dries at different rates, so a consistent application will make the process easier.

Mix the joint compound

Mixing the joint compound is a crucial step in skim coating drywall. The consistency of the mixture will determine how easy it is to apply and how well it adheres to the wall. Here are some detailed instructions on how to mix the joint compound for skim coating drywall:

Choose the Right Joint Compound

Select a lightweight, all-purpose joint compound, also known as "mud." This type of compound is easy to sand and serves almost no structural purpose. It is important to read the labels and choose a compound that is suitable for skim coating, as some manufacturers specify their products as "Not for Skim Applications."

Prepare the Mixture

Follow the mix ratio provided on the product instructions. It is often better to use slightly less water than the recommended amount to create a heavier, stickier product. This will give your skim coat greater strength and make it cleaner to apply. Mix the joint compound to a stiff, yogurt-like consistency.

Add Water Gradually

Determine the amount of water needed based on the manufacturer's instructions. Start by putting slightly less water than required into a mixing container or bucket. Then, add the joint compound to the water and mix thoroughly. After mixing, if needed, add the remaining water to achieve the desired consistency. Adding the compound to the water helps to achieve a lump-free mixture.

Achieve the Right Consistency

The ideal consistency for the joint compound is similar to that of thin pancake batter or mayonnaise. It should be thin enough to roll onto the wall smoothly. If it becomes too watery, add more compound, and if it is too thick, add a small amount of water.

Mix in a Separate Container

If you have leftover joint compound from a previous project, do not mix it with the new compound. Always mix the compound in a separate container to ensure a consistent and lump-free mixture.

Thin the Compound for Skim Coating

For skim coating, it is essential to thin out the joint compound slightly. You can use water or a thin texture compound to achieve the desired consistency. Start by adding a small amount of water or texture compound to the joint compound in a mud pan and mix thoroughly. Gradually add more liquid until you reach the desired consistency.

Test the Consistency

To test if the joint compound is ready, scoop a small amount onto a knife and press it against the wall at an angle. It should leave a thin, even layer on the drywall, filling in ridges and gouges. If the compound is too thick or lumpy, adjust the consistency by adding more water or texture compound.

Clean Your Tools

It is important to clean your tools after mixing and applying the joint compound. Rinse off your tools and mud pan with water, being careful not to pour large amounts of joint compound down the sink or tub to avoid clogged drains. Wipe down your tools with a wet rag to remove any excess compound and allow them to dry before storing.

By following these steps and taking your time, you will be well on your way to successfully mixing the joint compound for skim coating drywall. Remember to work in small sections and let each coat dry before applying the next one. With patience and practice, you'll be able to achieve smooth and seamless walls.

Roll out the compound

Rolling out the compound is the next step after mixing the drywall compound to a stiff, yoghurt-like consistency. The drywall compound should be rolled out in sections of about 2 feet wide by 8 feet high. The roller should be pressed firmly into the wall to force out bubbles. It is important to work in smaller zones to prevent the drywall compound from drying out. The drywall compound should be kept consistent across the surface to make the process easier.

The roller should be dipped in a bucket of skimming mud and rolled evenly on the surface to be skimmed. It is best to work in a section of four feet by eight feet. The drywall knife should be pulled tightly across the surface to remove as much drywall compound as possible. The key to roll skimming a wall is not to leave excess mud on the surface, as this would require more sanding.

The angle at which the drywall knife is held is important. The knife should be held at a high angle in relation to the drywall surface to remove more mud, leaving behind only a very thin layer. The left side of the knife should be pressed more than the right side to ease out imperfections on the left side and leave a low ridge on the right side.

It is important not to exert full force with the knife to avoid scraping off too much drywall compound and gouging the wall with the corners of the knife. Excess compound should be deposited in a tray. A second pass should be made adjacent to the first column, again favouring pressure on the left side to eliminate the ridge. Overlapping ensures that most of the ridges are taken care of by the drywall knife, leaving less drywall sanding for later.

Skim the first section

Skimming the first section is the most important part of the skim coating process. It is the difference between getting half of a wall done in two nights versus three in one night. To skim the first section, you will need joint compound, a mud pan, a wet rag, and a taping knife.

Firstly, scoop some compound into the mud pan and start adding water a little bit at a time, mixing as you go, until you get a consistency similar to thin pancake mix. Next, starting at the top right corner of your wall, scoop some mud onto your knife. At an angle, press the knife against and down the wall, leaving a thin layer of compound on the drywall. You will want to scrape the knife across the wall in such a way as to leave a little of the mud behind, filling in the ridges and gouges while skimming over the entire surface. Then, wipe off the knife on the side of the mud pan, and, using the same motion as before, scrape the excess mud from the wall.

It will take some practice, but with a steady hand, you will get the hang of it in just a few passes. Don't be afraid to go over the same spot if you don't like your first pass—the mud is thin and wet, so it's forgiving until it begins to dry. But if you find that you really liked your first/second/third try, stop. Little imperfections can be taken care of in a second pass once the first is dry and sanded. If you start to see the blade of the knife get gunky even after scraping the excess off, use a wet rag to wipe it clean and begin again.

You will want to continue doing this across the wall, but since the mud is impressionable until it cures, be careful not to overlap the edges of your various passes across the same wall, or else you will find yourself working to fix a patch of the wall you were already done with. You will be working on this for multiple nights, so it doesn’t have to be covered all at once. If it’s smoother-looking than before you began your work, you’re on the right track!

Sand the dried skim coat

Sanding the dried skim coat is the final step in skim coating drywall with joint compound. It is important to allow the skim coat to dry completely before sanding. This usually takes about an hour or two. Once it is dry, finish with a light sanding using fine-grit drywall sandpaper.

If there are too many peaks and valleys on the wall, it is recommended to start with 100-grit sandpaper before moving on to 120-grit sandpaper. Sanding the skim coat will smooth out any remaining ridges or imperfections and prepare the wall for priming and painting. It is important to wear a breathing mask and protective eyewear during the sanding process, as dust will be everywhere.

For larger projects or multiple rooms, consider investing in a hand or pole sander with sanding screens, which last longer than traditional sandpaper and do not clog as easily. A drywall hand sander kit with a vacuum attachment can also help to reduce dust by up to 90-95%. Proper lighting is also key to ensuring a thorough sanding job. Use a flashlight or work light to illuminate the wall from different angles and identify any areas that need further sanding.

After sanding, it is important to prime the walls before painting. Priming will seal the pores and prepare the walls for paint, ensuring better adhesion and a smoother finish. It is recommended to wait until the skim coat is fully dried before priming and painting, referring to the manufacturer's instructions for drying times.

Frequently asked questions