Fill RSJ cavity?

[CPEA]

Hi there,

We have an RSJ supporting the rear kitchen wall into an extention. We're in the process of insulating the extension roof, which one side of the RSJ sits in the roof space and the cavity in unfilled. The other side forms part of the kitchen wall and is double boarded. Does the empty RSJ cavity into the extension roof need double boarding or can roof insulation be fitted?


Thanks

 

[JerryM]

i think what you are saying is the RSJ sits on both the inner and outer leaf brickwork and effectively over the cavity.

i would use polystyrene sheet on the basis that it is easier to handle/fix. roof insulation will be just as good as long as it does not drop/compress with time and uncover the top part of the RSJ.