A bit about the hearth and the ovens brick floor

Posted by Rado on November 24, 2003 at 18:24:20:

Wall that holds the hearth slab: 77cm /that's 4 x 19cm concrete PC blocks if you used these, or 11 to 12 lain bricks/. 11cm for the reinforced concrete slab, hearth will be about 11cm as well which is the size of a refractory fire brick /as oven's floor/. Between the concrete slab and bricks you will make so called mortar bed, this is a thin layer only and is used to set the bricks into a nice surface. If mortar bed is 5mm, ovens floor will be in 1m height.

The "mortar bed": 1 to 1 ratio of a fire clay and a fine sand, sand as brickies use. Mix with water into soft mushy stuff, apply that on top of the concrete slab. Use an ordinary plasterers trowel tool /first you can wet the slab if too dry/.

Dry joints in between all fire bricks of the floor, just place them next to each other. Tap them with a wooded or rubber hammer after you put more of them into place, to level them up.

This concrete slab, use concrete as on the website /but don't add fire clay in the mix/. I make the same slab for the oven I build right now. It's a 82cm x 92cm internal measurements. I decided to make the slab mixing a concrete gravel with a 'Portland' cement /can get normally in building shops/ in the ratio 4 to 1, but with each shovel /part/ of the Portland cement I also add plus half shovel /half part/ of the lime. Lime is in fact a calcium and works well in heat and accompanies the Portland cement, that is a hydraulic cement used also for refractory concrete.

I never use a 5cm sand bed under the brick floor, this is sometimes done when a refractory precast domes are used. I haven't use these for building of oven as they are so expensive and some can peal and crack down the track.

You will have to find someone with a digital photo camera and take many pictures as you progress till the oven is finished, with your bodies on pictures as you go building, I will put them on the website. Can you do it please? I could make a special page or two just of yours, it would be very useful and practical for many other people then. Big help on the other hand. Have you noticed my new contact form look in my profile page, great hm? Web design is my real hobby.

I have realised you did a good research. What size internal will you choose?