Q: Why is the flagstone in my patio starting to flake off?
A: Flagstone is almost always sandstone which is made up of layers upon layers of sediment. The flaking is called spalling, which is a natural occurrence in sandstone. Moisture gets in between the layers of sediment and begins to slowly weaken the layers.
These weakened layers eventually separate due to the water freezing and thawing between during the winter. A heavy-duty rock sealant can help prevent this but will need to be reapplied every several years. Unfortunately, this is not a service we provide but can be done by any homeowner or handyman.