Valoriani Top 100 build render

[Intern1]

Hi been reading this forum for a while and read some of the builds but wanted some advise on render mix for a top 100 which is in under a pegola which will eventually be tiled.

I have seen 2 coates been recommended after blanket.

What is a better mix perlite or vermiculite? as first scratch coat?

Then for topping coat would you suggest pre mixed acrylic render or a made up mix with cement sand and lime, prior to tiling?

Cheers

John

[david s]

Hi John,

Valiorani do not provide the render or suggest recipes that can be used, unfortunately.
If you have a solid roof on your pergola it is better to have the outer shell porous so any moisture build up in the insulation layer will escape more readily.
But if you plan on tiling over the render, you'll need a stronger outer shell.
The addition of perlite or vermiculite to any mix severely compromises its strength and applying a strong render over blanket is difficult because the blanket is rather springy. My solution (and there are many ways to go) is to cover the blanket with a very lean (10:1) mix which results in an insulation layer with equivalent insulation value, per thickness, as blanket.
I find a combination of perlite and vermiculite (50/50) works better than either of them alone.Once this has dried I apply a 4:1:1 sand, lime, cement render enriched with AR glass reinforcing fibres about 15mm thick. This eliminates the need to use chickenwire.
Here's a pic of a 160 Valiorani I built which shows my method.

[Intern1]

Thanks David, so would you suggest not use the blanket and a 10:1 mix sand:cement, then a 4:1:1 ?

Have you seen a blanket used in tiled oven?

[david s]

No.I think you should se blanket, then a layer of 10:1 vermiculite/perlite and cement to form an insulative layer that’s equivalent to blanket in insulating value but firm enough to render onto.. Then apply a 4:1:1 sand, cement, lime render

Vermicrete or perlcrete can be used instead of blanket, but in application creates a problem of having to dry it out before firing. This becomes difficult if the layer is more than 1.5" rick and requires yhat it be done in layers with a week of drying between layers. The beauty of blanket is that it's quick and easy to apply but also dry. The drawback is that it's more expensive.