A skim coat is a thin layer consisting of some mixture of gypsum powder and water or a joint compound -also known as mud-that you can use to repair or smooth damaged walls. You may need a skim coat if you want to repair a crack, fill a wall or floor gap, or raise an area with a level surface. Apply a skim coat using a building press or drywall knife (a type of knife specially designed for flat gypsum walls for spreading building material mortar) on a rough wall or ceiling surface to create an even surface, so you can then paint the walls or apply paper. wall (wallpaper). In general, you should apply two to four coats of polish until the surface is smooth.
Step
Part 1 of 4: Preparing the Surface to be Repaired
Step 1. Protect the furniture and the entrance to the room from dust and splashes
Remove all furniture from the room to be repaired. Cover the floor with a canvas cloth or plastic protector. Cover the entryway with protective plastic-glue it with a special paint adhesive-to prevent splashes and dust from building materials from escaping the room being worked on. Remove the protective covers of light switches and wall sockets to prevent material splashing on their surfaces.
Step 2. Determine the damage to the walls or ceiling of the room
If there is a lot of damage (scratches, cracks, large holes), then you should fix this kind of damage first. Maybe you have to finish the work of joining the new gypsum walls; or maybe you're planning to repair a coating that's starting to crack because it hasn't been replaced in years or because of vibration. Maybe you just want to smooth out a ceiling where the surface looks like it has spots.
- Remove all nails from the surface to be skim coat. Fill the surface of the hole with the joint compound that has been stirred.
- Cover all cracks in the wall by first scraping the peeling wall area, filling the hole with a joint compound, then covering it with a special wall joint adhesive to prevent the crack line from expanding. Let it dry before moving on to the next step.
Step 3. Clean the entire wall or ceiling
First remove the dust, then wash if needed to remove the stickiness. Use a foam sponge or wet towel to wipe the surface. Use water or a cleaning product that is friendly to the walls, depending on the type and state of the dirt attached. Rinse the walls with clean water after using cleaning products.
- Sweep up any dust particles with a duster, or clean the walls with a vacuum cleaner with a dusting brush attached to the end.
- Wipe off light stains with a clean, damp sponge or kitchen paper.
- For more stubborn stains, try wiping the walls with a mixture of warm water and a mild detergent. Try scrubbing the stain with a paste of baking soda and water. Try mixing 237 ml of ammonia, 118 ml of vinegar and 59 ml of baking soda with 3.8 liters of warm water to make your own powerful cleanser.
- Consider using a surface cleaning product that is known to be good on the market.
Step 4. Apply a water-based primer/exterior paint on the surface, then let it dry
You will need to apply a skim coat over a coat of matte paint or primer. All types of surfaces that have been painted should be primed and then wiped with a cleaner. This will make the joint compound mixture adhere well to the wall surface, and will not smudge or bubble. If you have removed the wallpaper from the wall, paint the surface with an oil-based primer.
Part 2 of 4: Preparing Materials
Step 1. Find the right type of compound / mud joint
This coating mixture-sometimes also called “mud”-is composed of a mixture of very fine grains mixed with water. There are two typical material choices for skim coats:
- The type of joint compound that has been mixed can be directly applied to the wall surface. The coating will dry slowly after polishing. Therefore, you can add water to the mixture to extend the polishing time. For those of you who have never done a skim coat before, it will be very easy if you use a product whose ingredients have been mixed and are ready to use.
- The "quick set" mix is made from the same granular base as the joint compound above, but you'll need to mix it with water before using it. These mixtures are the same as concrete: they will not dry out. They undergo a chemical reaction that will make them "harden".
Step 2. Do not use spackle, a wall cladding that is based on gypsum plaster of hydrated calcium sulfate and glue
This type of coating mixture is often thought to be used as a skim coat. In fact, this material is more difficult to polish and sand. This material is better used on pieces of wood to fill gaps in large surfaces.
Step 3. Gather your equipment, including:
- Stairs or scaffolding to reach high places without wasting energy. This tool is especially important if you want to apply a skim coat to a high wall or ceiling surface.
- A large bucket (which can hold 19 l of liquid) for stirring the skim coat.
- A special drill whose eye is attached to a metal stirrer. This tool will make it easier to stir a large mixture.
- Special container for mixed building materials (mud pan).
- Skimmer plates. This tool will hold the polished layer to the wall. Hold the skimmer plate in one hand -or place it easily accessible - while you apply the skim coat.
- Choose the polish you like. You can use a paint roller or a tool that resembles a building mold with a flat surface. The tool should be 15 cm wider than the smoothed area. Use a tool that is 30.5 cm wide to raise and level the walls.
Step 4. Mix the "quick set" type ingredients according to the directions on the package
"Quick set" mixes are usually packaged in sacks, and you'll need to mix them with water before using them. The time limit is usually stated on the packaging of the sack - often 20, 45, or 90 minutes - which indicates how long the work process takes under normal conditions. Heat will shorten the working time and cold will prolong the working time. Make a small batch first: if you mix too many ingredients at once, the ingredients will start to dry in the bucket before they can be used.
- The benefit of this type of mix is that it will harden into a layer that can be sanded or re-coated as soon as it dries. It also means that you need to know the exact area you're going to polish and be prepared, as a hardened layer can't be re-wetted.
- This type of “quick set” mix is more durable than “mud” and will not change if it gets wet. The use of this material is ideal for walls and ceilings that are exposed to moisture, such as bathrooms and kitchens. A small amount of material, if dropped into water, will harden.
Step 5. Stir in the type of joint compound that has been mixed to make it runny
Stir the mixed joint compound in a bucket with the stirrer attached to the electric drill bit. Stir until the mixture is completely smooth, adding water if needed. The resulting mixture should have a custard-like mixture.
Step 6. Add any color you want to use
You can color any type of joint compound by adding it while the mixture is stirred. Look for dye products at a hardware store. You can also add sand or other coarse material if you want to give the layer a certain texture.
Step 7. While stirring, start by adding the required amount of water
Start stirring slowly until the mixture is combined, then increase the speed of the mixture. You can add more liquid slowly if you want to thin the mixture. Search an image or video on a search engine for "mixed joint compound" to see what the final mixture will look like once it's "ready."
- Stirring the mixture is the same as mixing cake batter. Remember, do not pull the stirring drill out of the mixture while it is still spinning, or the mixture will splash all over the place.
- It is very important that you make sure that there are no lumps in the ready-to-use joint compound. If you find lumps that are dry when you apply the material to the surface, you can crush the lumps until they are smooth and mix well with the surrounding mixture that is still wet. If the lump is too large to crush, remove it with a small putty knife.
Step 8. Ask someone to help you
Large buckets must be cleaned each time you use them, or the dried mixture debris will be carried away during the next mix preparation. Your assistant can transfer the prepared mixture from the bucket to a smaller container. From this container, use a polishing tool or small trowel to transfer the mixture into a special container to hold the building material mixture. Then your assistant can start cleaning the bucket and making the next mix of ingredients.
Part 3 of 4: Polishing the Surface with a Skim Coat
Step 1. Get ready to apply the first coat of skim coat
Determine the thickness of the coating you want, or specify the type of outer layer you want (from completely smooth to rough and textured). If you are right handed, hold the skimmer plate in your left hand and the polishing tool in your right. You may have to adjust your technique to get the thickness and texture you want. You can always add more mixture to the surface to be coated, but once the coating dries, the coating will become messy and clean up will take some time.
Step 2. Flatten the first mixture you placed on the wall
Gather the mixture at one end of the area to be coated, then spread it over the surface with a polishing tool. Do it with firm movements, and apply pressure in the direction of the wall joint/crack, the same as pulling a glass cleaner while cleaning glass, so that only a small amount of material remains on either side of the repaired area.
- Start from one corner of the wall, and from the very top side work your way down. If you're repairing a ceiling, start at the edges and work your way up to the center.
- If you've never done this before, try practicing on a small piece of gypsum board. That way, you'll get used to using the polishing tool as well as the weight of the mixture, and you'll be able to see how it looks when it dries.
Step 3. Keep applying skim coat over the surface of the repaired area
After you have polished and evened out the material mixture you first placed on the wall, take it again and coat the area you previously finished. Do it thoroughly-make sure that each new layer overlaps the previous one. Polish the layers in different directions to even out lumps and crevices, regardless of the direction of the initial stroke.
- The repaired area is not completely flat: this area is like a smooth, low mound, made to appear even. Illuminate the length of the polished surface with a lamp to see any concave areas of the wall, then mark those areas with a pencil as you look at other areas.
- Patience is key, but you'll need to work efficiently so that the mixture doesn't dry out before you've finished polishing. Take the time to complete one section first. Try not to stop polishing in the middle of the surface as it will be difficult to polish the wet material and mix it with the dry surface.
- Never do this in a hurry, especially by taking multiple mixes at once. This will tire your hands, and may knock your material off the skimmer, and you'll need to resurface the area later to get rid of the excess.
Step 4. Allow the first coat to harden for a few hours or overnight
Apply and apply fiberglass adhesive over cracks and joints. Allow the surface to harden or dry before you apply the next coat. If the repair area is deep/large, two to four layers will create a solid repair and a smooth surface. Don't overcoat the material or try to only coat it with one coat-this can only be corrected with a demo or a lot of sandpaper. It is better to polish each layer lightly but with many layers, than to polish unevenly which will have to be repaired later.
Part 4 of 4: Polishing the Finish
Step 1. Sand the wall
Use sandpaper with a smooth surface (180 to 220) to smooth out any rough edges. If you have marked the low areas with a pencil, you can blend them with the higher areas to make sure the next coat will adhere well to the surface.
Step 2. Polish a second layer of mixed material
This time, work in a horizontal direction, perpendicular to the first layer. Let it dry. Sand it again, and touch the surface with your hand to find out where it doesn't fit, which you can't see with your naked eye.
Step 3. Repeat as many times as needed until the surface is smooth
With each new coat, change the direction of the polish from horizontal to vertical to ensure an even finish on the wall. Make sure you allow enough time for the coat to dry, before applying the next coat.
Step 4. Clean the room thoroughly once you are done
Clean the walls with a vacuum cleaner and make sure that no dust from the wall plaster remains. Polish the primer before painting or pasting the wallpaper.
Tips
- To store joint-compound that has been mixed overnight: carefully clean the sides of the bucket of building material mixture after each work, and pour water directly over the mixture to a height of 5 cm. When you are ready to continue working, simply pour the water out and the mixture will be ready to use.
- For the first coat, some people choose to thin the mixture until it has a cookie dough texture, and then polish it with a paint roller. Then they use a special drywall knife or press to even out and smooth the layer.
Warning
- Wear a mask and eye protection when you sand. A headgear that is usually used for bathing or a swimming cap will prevent dust from spilling on your hair.
- Do not clean the tools you use in the sink or sink with a drain. The building material will stick, harden, and seal the pipe. Therefore, scrape off the excess material and throw it in the trash. Wipe the utensil with a coarse sponge or towel to make the utensil thoroughly clean.
