UK 34" rounded square Oven Progress.

[Frances]

Re: UK 34" rounded square Oven Progress.

I had the exact same problem... let me see if I can find the pics. Ok, they're right at the beginning of this thread:

http://www.fornobravo.com/forum/f9/p...nues-2991.html

I hope you can tell what's what, it was kind of difficult to take pics of it all. Basically I built a structure of rebar over the oven, and covered it with chicken wire and the carpet underlay bit by bit, filling with vermiculite as I went

Wiley did something similar, only 100 times more perfect:
http://www.fornobravo.com/forum/43/s...en-3717-7.html

Actually I'd follow his version if I were you, it really is a lot nicer!

[Nev Grady]

Re: UK 34" rounded square Oven Progress.

Yeh! The weather in the UK has been really crap for the past few weeks! Especially where I live in the northwest. Incessant heavy rain. No shortage of water here!

Is 50-75mm of dry vermiculite sufficient? Even if you do manage to form a render shell can you be sure that the dry vermiculite you pour in is spread evenly inside it?. Why not use all fibre insulation?

I first covered my dome (1 metre internal dia.) with 5 layers of heavy duty aluminium foil. This helps with any cracks which may develop and also reflects heat back into the oven. I then put on two layers of 25mm INSULFRAX. One roll was sufficient. This stuff is good up to approx 1250 Celsius. On top of that went two layers of 50mm thick ROCKSILK FLEXIBLE mineral insulation bought from B&Q (UK's Home Depot equivalent). One pack was enough. This is good up to 800 Celsius.

From the same place I bought 3 large sheets of plasterer's mesh which was cut to shape and wired together. This was then covered in ordinary undercoat plaster about 20-25mm thick followed by about 25mm of waterproof cement render. 2-3 days work should get you to the point of being ready for the waterproof render. The photo shows the insulation, mesh and oven opening not quite finished.

Works a treat. The oven heats up to temperature in about 1 hour, and with an insulated door in place it holds the heat extremely well.

[dmun]

Re: UK 34" rounded square Oven Progress.

I bought 3 large sheets of plasterer's mesh

Translation = expanded metal lath

This was then covered in ordinary undercoat plaster

really? a gypsym product? I wouldn't recommend this.

[hulkiebear]

Re: UK 34" rounded square Oven Progress.

thanks for the replies guys! some good ideas for me to work with! I never thought of plasters mesh!

I already have 2 layers of 25mm blanket, and decided I needed more, but I can't go much more than 2 or 3" of insulation with a render outer before I run out of platform to put it on.

[Nev Grady]

Re: UK 34" rounded square Oven Progress.

Translation = expanded metal lath
really? a gypsym product? I wouldn't recommend this.

Really? Why not?

[Nev Grady]

Re: UK 34" rounded square Oven Progress.

I can't go much more than 2 or 3" of insulation with a render outer before I run out of platform to put it on.

Is it possible to get extra width and depth by anchor bolting precast concrete lintels, or something similar, level with your hearth? They wouldn't be carrying too much weight.

[dmun]

Re: UK 34" rounded square Oven Progress.

a gypsym product? I wouldn't recommend this.
Really? Why not?

Gypsum products like plaster of paris and drywall will absorb atmospheric moisture when they are outside: they swell and stress whatever is on top or underneath, loose all strength, and fail.

There's a reason that plaster (gypsum) is used inside, and stucco (portland cement) is used outside.

[Nev Grady]

Re: UK 34" rounded square Oven Progress.

Well Mr Dmun sir, teaching grandma to suck eggs springs to mind, if you know what I mean. Undercoat plaster was used for ease of application and for its quick setting properties. There is no way that it can absorb atmospheric moisture, or any other moisture for that matter. As explained previously, it is totally covered by a waterproof render which in turn has several coats of a top quality masonry paint.

In the unlikely event of any moisture ingress and the failing of the gypsum plaster, would it matter? It was used as a thin base coat for firming up the plasterer's mesh to ensure keeping its shape before applying the cement render. If it fails nothing is going to collapse!