This is often caused by trapped moisture. When water trapped within the pore structure freezes, it expands by approximately 9%, exerting internal pressure.

Repairing a stone window sill is often more cost-effective than a full replacement, which can cost between . Most minor cosmetic or structural repairs range from $150 to $300 and can often be completed as a DIY project with the right materials. 1. Common Types of Damage

Mixing the patching compound was the trickiest part. It had to be the consistency of peanut butter—not too wet, not too dry. I worked in small batches because it set fast. Using the paintbrush, I dabbed water into the crack first, then pressed the compound in with the trowel, overfilling slightly. Then, the artist’s touch: while it was still tacky, I sprinkled dry sand over the surface and dabbed it with a wet sponge to match the original texture.

I gathered my supplies: a wire brush, a bucket of warm water with a little dish soap, a small angle grinder with a diamond cup wheel (borrowed from a skeptical neighbor), a can of masonry patching compound, a trowel, a spray bottle, and a stiff paintbrush. I also bought a stone hardener and a small bag of fine sand for texture.

This involves removing the damaged section and inserting a new piece of matching stone.