When outside walls need a new application of cement, rendering must be applied to the wall. Rendering is made during a process whereby sand, cement, and lime is mixed. The mixture is then applied to a wall to provide a finished look. Depending on the sand and application used, the wall can then be made smooth or textured.
Purchase the ingredients. Most people use about 6 parts sand, one-part cement, and one-part lime to make rendering. You can use either soft sand, or hard sand, which will give the mix a grittier feel. You can use regular cement found at the hardware store and lime that is used in masonry projects to help reduce moisture from seeping into the rendering mix.
Measure ingredients for accuracy. For a more consistent measurement, use a container, such as a small bucket, instead of a shovel. Be sure to level each time.
Add the ingredients in a wheelbarrow or other large container. Add small amounts of water to the valley using your trowel or a small shovel to pull the rendering mix toward the middle. Continue turning the mix and adding small amounts of water until the consistency is solid enough to sit on the trowel without running off. It is now ready to apply to the wall.
Wear protective clothing, especially since you'll be working with lime. Practice making rendering in small amounts to get the consistency and feel you want. Mix one wheelbarrow (or container) of rendering at a time and apply to your wall promptly so it does not dry up.