It is applicable to dwellings that are subject to planning conditions that prevent occupancy for a continuous period of at least 28 days in any 12 month period.
Mae'n gymwys i anheddau sy'n ddarostyngedig i amodau cynllunio sy'n golygu na allant gael eu meddiannu am gyfnod parhaus o 28 diwrnod o leiaf yn ystod unrhyw gyfnod o 12 mis.