30 firefighters were called to a property in Ystalyfera, near Swansea, at 1710 hrs yesterday evening after a grass fire spread to two properties.
The fire in Woodmans Terrace is said to have severely damaged a single storey property as well as a detached two storey building. No one was injured.
Firefighters across Wales are launching "Project Wildfire" to help tackle deliberate grass and mountain fires.
Firefighters were called to a street in Swansea yesterday after a grass fire spread across two properties.
There was a rise in grass fires this weekend as temperatures increased across Wales.