How to render a wall
At some point or another a homeowner may be faced with the task of plastering concrete walls to change the appearance of the wall, make it resistant to moisture, eliminate unsightly cracking, or to add texture. Rendering kitchen, bathroom or concrete living room walls is easy and the finished wall will be able to withstand abrasion.
Follow these instructions to plaster the concrete block walls
Step 1: Prepare Your Concrete Block walls –
Before you begin to plaster your concrete walls, you need to remove peeling paint and flaking bits of old plaster. Your walls should be free of paint, oil, and dust so the plaster can bond properly.
Caulk cracks and kill any mold on the walls. Use a wire brush to clean stains left by the mold or mortar joints.
Step 2: Apply a Layer of Dash –
The texture of the concrete walls should be sufficiently rough so the plaster will adhere to it. To help achieve this, you need to make dash by mixing one-part cement to 1 1/2 parts coarse sand and add enough water so the mixture has a runny consistency. Apply a coat of the mixture to your concrete wall before plastering it and allow it to dry for a day.
For a flat finish apply a layer of dash that is almost liquid in consistency.
Step 3: Mix the Plaster –
Mix your plaster according to the manufacturer’s instructions, preferably in an area away from drying winds and direct sun. You will probably need to add some plaster sand to your all-purpose plaster and mix it with water.
Make sure you use the batch within about two hours. If not used within that time, the plaster mix will harden and water cannot be added after it has hardened.
Step 4: Apply the Plaster –
Apply a base coat of plaster over the layer of dash with a steel trowel. The layer should be somewhere from 10 to 15 mm thick. Apply it in small strokes, making sure it is level and uniform. If you want a flat wall, smooth the plaster out. Leave it rough if you prefer a textured look.
If you want to apply a single coat of plaster, make sure it is no thicker than 10 to 15 mm. Remember the thickness of the top coat should be 5 to 10mm.
Step 5: Care of your Plaster walls –
Once you have successfully applied plaster, it is imperative you protect your walls from the sun and wind. You can do this by covering them with a plastic sheet the size of the walls, or by using several pieces of sheets joined together for larger walls. Keep your walls moist for a minimum of seven days for the plaster to set properly.
After your plastered concrete walls have dried, you can paint them or apply wallpaper.
Materials and Tools Checklist :
The key to starting off this style of project is the equipment, correct tools and materials for the job and having them all close to hand. Quantities of the following materials will vary depending on the size and sub-base requirements of your project.
- NGM Blocks Cement Bags
- NGM Blocks Aggregates and dried Sand
- All-purpose plaster
- Plastic sheets
- Coarse sand
- Wheel barrow
- Steel trowel
Please use Personal Protective Equipment when carrying out this work, such as safety shoes and gloves. Gloves, Safety Goggles, Dust Mask, Ear Defenders, Knee Pads.