We frequently install grab rails directly on concrete walls. It is important to avoid working too close to the wall's edge, more specifically on an outside corner, and especially when the wall is covered with stucco. Stucco can be brittle and can break off when one drills too close to the edge. 

When drilling through harder and uneven materials, it is important to ensure that your holes are accurate and match up well to your template.

We like to use a fresh, high-quality masonry bit set on hammer-drill mode when preparing a concrete wall for grab bars. If the wall is covered with stucco, we prefer to use a smaller diameter drill bit to create a smaller hole. This helps to ensure the accuracy of the holes. We then progress to the hole size required for the wall anchors.