Different products, including joint compound and patching compound, can be used to smooth or repair different types of walls. The putty is particularly suitable for plaster or concrete walls. The product will fill small cracks and holes, by applying a few thin coats over the entire surface, you will be able to smooth the wall and help the paint to adhere better. Just make sure you prep the wall well and mix the putty properly, apply it in thin layers, and let it dry perfectly before continuing.
Part 1 of 4: prepare the work area and protect yourself
Step 1. Put on gloves, eye protection and a mask
As you clean and prep the wall, you'll create dust particles that could irritate your lungs and eyes. To be safe, wear protective glasses and a mask also to apply the sealant. In addition, the product could irritate your skin and it will therefore be better to wear gloves as well.
Also keep your protection on when you apply the primer or paint, as even modern products can give off irritating fumes
Step 2. Cover the items to be protected with masking tape
Use this adhesive to cover items that you can't move but don't want to put putty on, like window sills or door frames. If the floor of the room is finished, cover it with drop cloths or a tarp.
Take a little time to cover what needs to be covered, so you don't have to spend hours cleaning up spills afterwards
Step 3. Scrape or sand any chips, scales and bumps
If you are working on a new wall, you shouldn't have to scrape or sand. However, on an older wall, use a scraper or heavy sandpaper (40-60 grit), or both, to remove any paint, primer, or plaster flakes. With the sandpaper, smooth out any small bumps before moving on.
If you notice any tiny holes or cracks, no more than 1.5cm wide or deep, use the tip of a screwdriver to scrape the loose material. Holes or cracks larger than this will not be able to be filled with putty and will need to be repaired with another method
Step 4. Brush the entire wall with a dry brush
Brush the wall carefully, to remove any remaining scales, as well as dirt and dust stuck to the wall. You can use any solid brush.
Keep your mask and goggles on, as you will knock off dust while brushing
Step 5. Wipe and dampen the wall with water and a clean sponge
Immerse the sponge in a bucket of clean water, wring it out lightly and run it over a section of the wall. Repeat the process, until you have wiped the entire wall. The wall is now ready for the putty.
- Don't worry if the wall is still wet when you start applying the sealant - it will even help it adhere better.
- You can also use a clean cloth instead of a sponge.
Part 2 of 4: prepare the paste and repair the wall
Step 1. Pour the water into a bucket and add the powdered product
Read the product's instructions for use to know the proportions to respect. Pour the water into the bucket first, then add the correct amount of powdered filler.
- Prepare an amount of dough that you can use within 2 hours, as the product will then be too hard for you to work with. If you are not sure how much to prepare, prefer to prepare less for now, then prepare more if needed later.
- To keep the material moist as you work, cover the bucket with a damp towel.
- The powder coating is cement based and can be applied indoors or outdoors, on plaster or concrete walls. The paste putty is acrylic based and it is only recommended for interior use, especially for repairing painted walls.
Step 2. Mix until you obtain a homogeneous preparation
The easiest and fastest way to prepare the plaster is to use the mixing tip of an electric drill, set on low speed. However, you can also use a stick or other similar utensil. In any case, make sure that the powder mixture is perfectly incorporated and that no lumps remain.
- The preparation should have a thick consistency, without appearing dry. If you take a dose on a putty knife and hold the tool aside, the material should fall out in a large clump.
- If necessary, change the consistency by adding more water or more powder.
Step 3. Apply putty to small holes and cracks
Take some paste on the blade of a small putty knife (about three to four inches wide) and squeeze the material into the hole. Then scrape the surface of the area with the blade, horizontally and vertically, to remove the excess product.
Use the sealer to fill cracks and holes that are no more than 1.5cm in width or depth
Step 4. Let the material dry, sand and wipe dry
Let the product dry for at least 4-6 hours or even 12-24 hours in a humid environment. Then smooth the area by sanding it lightly with fine sandpaper (300 to 400 grit) and wipe off the dust with a clean, slightly damp cloth.
If the putty feels wet, to the touch or in appearance, wait a little longer before sanding it
Step 5. Apply primer to repaired area or entire wall
With a brush, cover the repaired area with a coat of primer, suitable for the environment. For example, if you are working on a concrete wall outdoors, use a product specifically designed for it.
- You may prefer to cover the entire wall with a coat of primer. If you plan to apply sealant to the entire wall after repairing it, check the product insert to see if the manufacturer recommends primer on the bare wall before applying the product.
- Even if you don't plan on applying the sealant to the entire wall, you could apply the primer to the entire wall before repainting it. Thus, the repaired area will blend better with the rest of the wall and the paint will adhere better to the surface.
Part 3 of 4: apply a first coat to the entire wall
Step 1. Take a dose of putty on a small trowel
Patchers are typically applied with two flat-bladed trowels (large putty knives), each held in one hand. The smaller of the tools will have a blade about 6 to 8 inches wide and the larger one will have a blade about 12 to 12 inches in width. Use the small trowel to place a mass of material on the large trowel.
Spread the mass of filler along the blade of the large trowel, so that it extends almost from end to end
Step 2. Squeeze the blade of the trowel against the wall at an angle, and scrape up
After placing the material on the large trowel, place its blade at the bottom of the wall, at an angle of about 30 °. Keep this angle and scrape the hole straight up against the wall, without detaching it. This will apply an even layer of sealant about 3 mm thick.
- Go from the bottom of the wall to the top, in one movement. If you can't get to the top of the wall, go as high as you can. You can use a ladder later to work the upper part of the wall.
- Don't expect to master this maneuver the first time. The applied layer of material could be too thick or too thin and leave bare areas on the wall. If you applied too much product, scrape it off completely and start over. On the second application, put more pressure on the blade. If there is not enough product, iron the area, pressing less hard on the blade.
Step 3. Spread the plaster on the blade again or add more
Once you've applied a vertical strip of putty to the wall, take a look at the larger plank. If there is a fair amount of putty left on it, just use the small trowel to spread it more, if necessary. If you need to add material to the large blade, take some material from the pot with the small trowel.
With practice, you will be able to scrape both blades quickly to add, remove and reposition material as needed
Step 4. Continue to apply the material from the bottom up
Drive to the right or left of the strip of sealant applied first. Place the trowel at the bottom of the wall again. Overlap approximately ¼ of the width of the plank on the first strip of plaster. (e.g.: 8 cm for a 30 cm wide blade). Apply a thin strip of putty, the same way you applied the first one.
- Continue to add filler to the trowel when necessary and apply the product, until you have covered the entire wall
- If you need to cover a narrow space, apply the material directly with the small trowel.
Step 5. Let the plaster dry for 16 to 24 hours
The putty should dry completely between coats, so it will be best to let a full day pass before applying more product (or moving on to the next step, be it sanding or primer application). In a dry environment the sealant will dry in 16 hours, in a more humid environment it will take up to 24 hours.
To see if the product is dry, touch it with your fingers and see if any areas are still wet
Part 4 of 4: apply a second coat and finish the wall
Step 1. Apply the second coat, horizontally or vertically
There are different opinions on how best to apply the second coat of sealant. Some people prefer to reapply the material vertically, like the first time. Others prefer to apply it horizontally and claim that the surface is smoother and requires less sanding afterwards. In any case, you will have to prepare the product, take it on your two trowels and apply it to the wall at the same thickness as during the first application.
- Horizontal application does not differ from vertical application in terms of technique. Hold the trowel blade at a 30 ° angle and do not detach it from the wall.
- The second layer, like the first, should not be thicker than 3 mm.
Step 2. Let the paste dry, sand and wipe off
Once the second coat has been applied and has dried perfectly, go over the wall with a fine sandpaper (grit 300 to 400). When you are finished, wipe off any remaining dust with a damp cloth or sponge.
If the material has formed bumps, sand them with a thicker sandpaper (grit 40 to 60), then smooth the surface with a fine sandpaper
Step 3. Apply primer and 2 coats of paint to the entire wall
Now that you have finished applying the sealant, protect it with a coat of a primer suitable for the environment (e.g. a product formulated for exterior concrete walls). Apply it to the wall with a roller or brush and let it dry according to the manufacturer's instructions. Then apply 2 coats of paint in the same way, allowing each coat to dry for the time indicated, before continuing.