Help with insulation and flue

[Bandit]

Finally managed to complete dome on my 32 inch WFO.
Thank you forum posters for all the fantastic information and pictures !

Can an I get some advice
Will be ready to put my ceramic blanket and chicken wire on soon.
i have 4m 25mm blanket. - hoping it’s enough for 2 layers and going to put 1-2 inches of 9:1 vermiculite cement over chicken wire.

On the pro/commercial ovens videos they had the hindsight to put a concrete under and then screwed the chicken wire and tensioners to hold the blankets in place. Saw the Melbourne fire brick company used aluminium flashing and high temp sealant to prevent water going into blanket/oven.

https://m.youtube.com/watch?v=d82oL0001Oc

Do you need to fix chicken wire to screws/base and can I do this to the vermiculite base?
I do not have a concrete plinth and was worried about drilling and putting a screw in the refractory brick base as this may expand with heat

Do I need to put blanket over front arch and flue ?


Is water going into into insulation an issue and is it worth using Aluminium flashing and sealant for outdoor uncovered oven?

Also wish I had used more insulation on my floor and invested in ceramic board. Have about 2 inches of vermiculite cement sitting on marine plywood on concrete slabs.

is there any way of adding more floor insulation at this stage ? it worth sticking insulating board under the marine plywood - would have to leave some gaps where concrete bars are!


Thanks for advice

[david s]

Most builders hold the blanket in place with chicken wire. As it’s in the middle of the oven’s insulation layers and it’s highly conductive, it seems counterintuitive to me. The chicken wire is also laborious to fit over a compound curve. Consequently I don’t put any there, but vermicrete straight into the blanket as you can adjust for the ballets lumpines as you go. The blanket I use(Superwool) is a dream to cut. You can accurately cut angles and fit pieces in perfectly.

Some builders lay some chicken wire under their insulating slab so there’s something to tie onto.

If using foil remember that as well as keeping moisture out it will also keep it in. If placed against a conductive material like refractory, concrete or brick it won’t work as a heat reflector as it’s highly conductive itself.

The flue gallery is generally insulated but the outer decorative arch not.

Yes water under the floor is an issue. If you haven’t already done so drill a few holes through the concrete supporting slab so moisture will have a path to escape. The heat will push it out.

Marine ply is a poor choice to build an oven on as it will be constantly moist for a long time, a stretch for any ply.