Floor problems

[Hestopesto]

hi all, I have a portable oven made from fibreglass, cement and vermiculite. I bought it so not sure exactly of the make up. The floor is just cement (no bricks) on vermiculite insulation board I think. Over the past few years we've been getting some cracks. I've repaired these with cement but it mostly came up again. This year I realise Vitcas sell a product especially for outdoor ovens. I took out all the loose stuff ( right back to the insulation in places, bit scary!) Unfortunately this has mostly chipped off too on the first firing. Can anyone advise me as I really need to get it working for a party next month. I'd really like to cover the whole floor in a new layer of something which will level out and set hard. Thanks in advance.

[UtahBeehiver]

I suggest you post a picture of your oven so we can get a better idea of the issues. Also, David S is our forum expert on cast ovens and might be able to give some insight to how to address, I assume, a single poured (maybe, refractory) floor. My guess is that the thermal expansion of a single piece floor is causing the cracking problem. A possible solution, if you have room, is to add fire brick "splits" which typically, 1.25" x 4" x 9" on top of the degrading floor.

[Hestopesto]

Here's some photos.

[david s]

Large pieces of any refractory material are subject to cracking because of uneven heating and therefore uneven expansion, particularly on the floor. Most ovens are made with loose bricks on the floor so each brick can expand freely. A few cracks in a single one piece floor cast are no problem and are unlikely to get worse, depending on the material used in the casting. Coating the whole floor in a thin layer is unlikely to be successful as you have found. You could create a layer of thin firebrick laid loose over the top of the existing floor although this will increase the heat up time a bit. Your single piece cast dome is also likely to develop some cracks, probably the worst one right at the back running vertically. Ignore it as it won't get worse, it's just the oven finding its own way of coping with the heat expansion. Most precast are made in sections to deal with this problem. Remember that there are two kinds of ovens, those that have cracks and those that have owners who lie about their ovens having cracks.