GN85 Efflorescence on Concrete Roof Tiles

One of the most common enquiries received by NFRC relates to these white marks, often leading homeowners to question whether their roof has been incorrectly installed or whether the roof tiles are defective.

In the vast majority of cases, these deposits are efflorescence, a naturally occurring characteristic of concrete roof tiles and other cement-based building materials. This guidance explains what efflorescence is, why it occurs, its effect on the performance of a roof and when further investigation may be appropriate.