closing cavities at the top

[mortarboard]

I'm at the top of my walls and I have been told I must close the cavities along the top. Could anyone tell me what is the best (Building Control) way to do this. I have been told to use slate or soffit board or similar. Also, I'm not sure if whatever I use should be bedded down on mortar or what?

Many thanks

[welsh brickie]

slate you can use also asbestolux boarding

[thedoctor]

See the project section.Cavities & Lintels

[mortarboard]

Many thanks