Built a large oven a few months back. It worked beautifully with the exception that it was not holding its temperature. I realised I did not insulate enough. Going to take it apart and start again from scratch Would like to get it right this time. What would be the best option for the base insulation? A vermiculite concrete mix of 15cm? Or is there a better option? I would lay this on the concrete hearth I constructed originally. I would then lay the firebricks on top of this. Appreciate any help or tips for materials!
As you've discovered you need to insulate the cooking floor and there are a number of options; thermolight blocks laid on their sides will provide a 10cm insulating layer. Vermicrete is another option but needs to be left to dry out before covering, insulating board is thinner but very effective albeit more expensive. folk have also used wine bottles lain in mortar but i've no idea how efficient these are. I used 25mm thick vermiculite sheet but mine is in an enclosed tray.
Remember that cooking floor height is critical and should be at the elbow height of the main user, therefore your choice of underfloor insulation may be dictated by this.
Thanks for the advice. The cooking floor was actually a bit low so it will suit to raise it.Have ordered in the Vermiculite and concrete with a view to starting this week. Will send in pictures once it gets going. Am thinking storage heater bricks on the base and then spend some money on some good bricks for the main build. Do you have any advice on what would work best and where I can find them?