Registered Construction Detail: Separating floor between dwellings

This Detail is in the vertical masonry that passes between dwellings. It’s a requirement to fire stop any cavity where it is not fully filled. The fire stop should achieve the required fire resistance and include a cavity tray (where required) and weep holes.

Whilst it’s not a requirement of Approved Document B, a fire stop is recommended by MIMA and most structural warranty providers if the cavity is fully filled.

How to get it right

• Keep cavities clean of mortar snots and other debris during construction
• Seal between the wall air barrier and the floor above and below the connection with a flexible sealant
• Seal all penetrations through the inner leaf with a flexible sealant or purpose-made shoe, which should itself be sealed to the inner leaf
• Separating floors require additional layers and components to comply with fire and noise requirements
• Cavity barriers may require an additional vertical DPC and/or cavity tray.

Find out more by downloading the Separating floor between dwellings fire detail.

Further information

LABC Registered Construction Details (RCDs) are a set of thermal details designed to minimise heat loss through weak points in the building envelope. They are free for everyone who works with local authority building control.