Perlite Portland mixture

[russ randolph]

Hello and thanks in advance. I am building a 42" Pompeii oven. I am to the point where my dome is done. I have put a 1" ceramic fiber blanket around dome and have covered with metal lath. I know it called for 3" of fiber blanket but was hoping to just add perlite Portland mixture to this to make up for the 2" I am lacking. Question is how thick do I need to make this layer? I will not have a structure around the dome. I plan on laying regular brick on the outside of the dome for the finish. Appreciate any feedback. I would post a picture but am not to computer savvy and cant figure out how to post picture from my desktop

[UtahBeehiver]

4" at 8 to 10 to 1 p or vcrete equiv. to about 2" of ceramic blanket

[russ randolph]

Thanks. do you believe it is necessary to do this at 4" thick even though I will have 4" of brick on the outside of that?

[david s]

Hello and thanks in advance. I am building a 42" Pompeii oven. I am to the point where my dome is done. I have put a 1" ceramic fiber blanket around dome and have covered with metal lath. I know it called for 3" of fiber blanket but was hoping to just add perlite Portland mixture to this to make up for the 2" I am lacking. Question is how thick do I need to make this layer? I will not have a structure around the dome. I plan on laying regular brick on the outside of the dome for the finish. Appreciate any feedback. I would post a picture but am not to computer savvy and cant figure out how to post picture from my desktop

Adding a layer of vermicrete over the blanket is the normal procedure as it adds insulation and allows you to get back to the hemispherical form covering lumps and bumps of the blanket. A 10:1layer of around an inch and a half will dry pretty well, if left uncovered and not rained on, in a couple of weeks. Any thicker and it’ll take ages. It also provides a firm substrate to render against.
As you are not intending to render over it you could get around the moisture problem by bricking up to the blanketleaving a little space that you could fill with dry vermiculite as yo build higher. The dry vermiculite is far easier to place than a vermicrete mix and has a much higher insulation value, around the same as CF blanket.

[russ randolph]

the brick I installed around the base is the brick I will be putting around the dome.

[UtahBeehiver]

You asked what the equivalent make-up of v or pcrete thickness to make up the 2" of ceramic blanket. Brick is not an insulator.But you could do as David suggest and leave gap and fill up with dry material but it does settle out.