Silicon on slates

[bcollet]

Dear all,

Is it common practice to use silicon to make a roof water-tight ?

like in the photo below (around a velux):

Thanks

Bertrand

 

[simon_d]

only thing i would be concerned about if the heat in summer. roofs, especially darker colours can get very hot

 

[markie]

No its not, it looks like in my opinion that who ever put the velux in has put silicon there because the slate underneath is broken.
It is common practice to put silicon underneath the last couple of slates at the top of the velux because there is no way you can nail them down.

 

[splinter]

I'd be more concerned about the slates being the wrong way round