Block Cavity Wall Question

[nitro23456]

Hi all

Silly question and just wondering really.

My house is block cavity and rendered. Both skins are block. Built circa 2000.

The interior skin of the cavity has much lighter softer blocks than the exterior skin. What are these likely to be? They are really quite soft, to the point I can just hand screw a screw into them without pilot holes or plugs. The outer skin is proper solid to the point I need an sds drill rather than a combi.

 

[jks7492]

Thermalite

 

[phatboy]

Thermalite / Celcon / Durox types of aircrete. That is pretty common in that age of building. You probably have foam sheets in the cavity, too.