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What size perlite for dome render

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  • What size perlite for dome render

    Hello all,

    I am looking for some information about the grade of perlite for rendering the dome of my (nearly) built dome. When I look at information on the grades, it looks like a fine grade (P10s) is used, but I am really struggling to find any in the UK. I can get medium horticultural grade (2-5mm), but no smaller.

    I have seen posts regarding the size for an insulating slab, but not specifically for render. Does anyone have any preferences/opinions on this.

    Many thanks,


  • #2
    Hi Colin,

    I believe that "render" in the UK refers to "stucco". If so, you don't need perlite for that mix. If you are referring to insulating the dome, medium grade perlite will work just fine. The insulating layer for the dome calls for the same grade of perlite as does the floor insulation. It just needs less portland cement in the mix.
    Joe Watson " A year from now, you will wish that you had started today" My Build Album / My Build