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Creating hearth floor with firebricks

Creating firebrick hearth floor on a thinly spread 50:50 sand-clay bed.
Masterly Tail oven design (3G MTo) – 3G MTo Main Page

1. Note images #0610 to #0627 relate to mixing the “clay sand bed” for leveling firebricks into a nice and smooth brick hearth floor surface. Note the importance of sifting of the sand (to remove every little pebble out – if any mini stone is under a firebrick while it’s put in place, it nearly always results in lifting that brick, removing the stone, and then placing the firebrick into the same spot again.) Plus 50:50 mixing ratio of fire-clay with a fine sand (I use loam which is a local name for the sand our brickies use for laying house bricks.) All that info is described in further detail on the building details page and its subpages.

5. Making firebrick hearth floor

Part 5 Creating “firebrick hearth floor” on this page is contained 68 photos.
Total images for work with firebrick is 613 images: #0697 – #1309 (out of 2,785)

Firebrick oven stages:   Floor   –   Walls   –   Arches   –   Dome Entrance

3G MTo main page.

There are also the Swishy oven and Original MTo designs for consider and they might just be positive to look at.

Respond to the Creating hearth floor with firebricks article:

15 Comments - post your thoughts

  1. By looking at your firebrick job, and thinking about it, this work does not seem too difficult for me. We will find out if my floor how I make it will have da same fine finish or just close. Thanks for your help Rado it is truly great help.

    By ScottPermalink

  2. Hi Rado,
    I hope you don’t mind me asking another question but I am about to start the dome and feel the firebrick I bought “new” are not square and tight therefore there are a few gaps in the hearth floor? It’s only a few not the total floor but wondered if it was ok or if I should spread some ash in the gaps – then add a little water? or just leave it as is?

    Thank you,

    added by Rado:
    Hi Brent,
    I am sure the floor is just fine; if there are some gaps do not worry about them at all, the ash will pack in the gaps on its own when the oven will be used. This happens often with uneven firebricks. In walls you can use, spread on thinly, a premix heat resistant mortar to even out the slight differences in firebrick sizes. Just a little of the mortar will be needed, only where required (if required) by the firebrick dimensions, when they vary in size. Don’t add water, leave the ash to pack in naturally.

    Just ask questions when you need! No any problem at all with that!

    By Brent — Permalink

  3. Hi Rado –

    Thanks for being so helpful and I have yet another question. I purchased Vesuvius Super 3000 refractory mortar. Can I use a very thin layer of this to set my fire bricks on instead of sand with clay? I have some pits in the concrete platform I’d like to fill in.

    Thank you

    By Kay — Permalink

  4. Hi Kay,
    I don’t see why not if it’s in a thinner layer. Every refractory mortar has own mixing instructions, follow what’s mentioned on the bag. If the mortar was already premixed in a bucket and it appears to you a bit more soft try to add/mix in fine sand, sieved sand as per image #0586 above. For the surface it will do good. If the mortar was setting too quickly then mixing into it a little bit of normal vinegar (tbsp) slows down the hardening speed (same way like with plaster.)

    By Rado — Permalink

  5. Thanks for the marvelous plans Rado.

    Where do you get your firebricks from and what sort of price each?


    By Andrew — Permalink

  6. Hi Andrew,
    We get all refractory, firebricks, fireclay, premix air set heat resistant mortar, non-refractory red clay house bricks and same clay pavers, from Claypave Pty. Ltd., locally.

    Type “claypave” in Google, it’s Australian company, big yard too, their firebricks are most accurate that I know of and to my knowledge it is the lowest price, around $3 per brick when it comes to retail. On their site they have list of retailers/distributors places who sell their products, see for New South Wales state there must be several locations available. Actually here is their webpage link:

    Many places resell their stuff each for various markup, so just shop around. Sometimes is cheaper to have delivered straight from them, that is the manufacturer. Few of my customers from overseas ordered from Claypave, refractory for one job it all fits on one wooden palette.

    Also we always watch these ebay pages it allows to save heap$.

    By Rado — Permalink

  7. Hey Rado,

    Thanks for this.

    One question if you would… There’s a guy close by who’s selling a lot of used fire brick. But most all of it is chipped along the edges, which will not result in as tight a fit as with new.
    Would these used, chipped bricks pose any sort of technical problem or just cosmetic?

    Thanks again,

    By Alex — Permalink

  8. Hi Alex,
    Yes, if not ridiculously damaged then it’s just cosmetic problem. But always turn them to point the better/nicer side towards the inside for the hot face. A bit of kink does not matter at all. The worst bricks can be used in the floor along the sides and the real bad ones under the walls around. It’s common, there are always many chipped firebricks also among new ones on a pallet.

    If in doubt email me a couple photos for the detail I will have a look and let you know.

    Just wondering how many firebricks does he sell? How much is he selling them for? Perhaps he got seconds somewhere and selling it with a small profit now. Lucky you maybe.

    By Rado — Permalink

  9. Hi Rado,

    I am unable to source fire clay here in Malaysia.
    What would be a good substitute to bed the firebricks for the oven floor?
    Could I use refractory mortar?

    Thanks again for a great web site!


    By Poul — Permalink

  10. Hi Paul,
    Either find a potter who would give or sell a bucket of clay or mix a little of fine sand (sieved without pebbles) into the refractory mortar, to make it just slightly weaker in the sense of bonding agent amount (would need to spread for aligning only one raw of firebricks at a time, due to faster setting of the stuff.)

    If you got the clay, cut it into thin slices with a wire first and dry them. In sun or moving air it dries out water fast. Then you can brake it into coarse powder easily (but it needs to be dry, both for powdering/breaking it and also to mix it with sieved sand and water eventually.)

    By Rado — Permalink

  11. Ta Rado,

    I’m sure I’ll be able to source some clay hereabouts. We’re only a few clicks from the Claytan factory!
    I didn’t realize that it’s just dried clay.
    She’ll be right.


    By Poul — Permalink

  12. Hi Rado,

    I found the plans I downloaded from you several years ago. I have a question. I have an opportunity to get new firebricks for a dollar a piece. I can get arched, rectangular, double-wide & even double length – the doubles at a premium.

    Anyhow, I have to purchase by the pallet. My question is approximately how many firebricks would you guesstimate I might need? I already have 3 pallets of red bricks I got for the best price: free. These will be used for the outside of the oven.

    I realize this question is dependent on the size of the oven. I am looking for a guess. I have no problem with having too many firebricks being I am somewhat of an amateur blacksmith with interest in crucible, as well as making traditional Japanese steel.

    Thanks in advance,


    p.s. I realize I could answer my own question if I drew this out, but my time is limited at the moment & I need to get the firebricks before someone else does. Thanx

    By Tony — Permalink

  13. Hi Tony,
    Have you emailed me during ~last weekend with photo-s of your kiln for work metals? I saw it. Friend of ours also makes knives at home, imitating some type of Japanese steel, like maps/texture-lines on the metal surface, real high quality knives with beautifully crafted handles. He recycles German and Swedish steel usually obtained from car wrecks.

    If I were you, AT THAT PRICE I would buy – invest into – all those firebricks you see on offer. These bricks can be resold very easily for double the price, in the actual fact better investment than buying gold or silver nowadays (and so for other tools and material for making other tools or food.)

    Don’t know exactly the size of those tapered firebricks you can get but if you add 20% in addition onto the firebrick count than the total brick-count will work out well. Always better to have a few left over than to be in minus or deficiencies in material resources (that is in a case when you do not buy the lot.)

    Here is the exact count of firebricks you will need for building the oven plus other blocks n’ bricks also needed. Notice that at the end of the content on this page you have there also the firebrick part dimensions on pdf files.


    By Rado — Permalink

  14. Here is a link for some fire bricks, dimensions are 9″ X 6″ X 3 5/8″ (3.625″) and $3.50 ea., that are local to me. I am not sure if they would work or not for an oven. Fellow selling them says they weight about 19 lbs.
    I would appreciate your thoughts.

    Craigslist: large never used fire brick

    By Henry — Permalink

  15. The firebricks this fellow is selling are made of proper material. Their special dimensions make me think as to where to use them so they fit. Not in arches as these firebricks are too thick for arches (although can be used for side arch brick cut to size though, the skew firebrick.) Because of their thickness 3-5/8 inch and 6 inch width you could put them in the hearth floor standing on sides at those 6″ height (6 inch floor thickness … would make it 1.5″ thicker compared to standard 4.5″ wide firebrick size. I never put firebrick flat, like tiles, in floor, that’s not good practice. More heat absorbing mass in the floor lets you cook and bake and dehydrate MUCH MORE varieties.) You can put them in walls, also at 6″ thick walls. If walls have different height, e.g. if a wall is lower, it doesn’t matter because the arch can be created of any width and the total arch rise/height from the wall point. However for arches thinner bricks are required, ei. 2.5 inch or thinner. The 9 inch long side is the normal standard length used. The ad doesn’t tell how may he has. These firebricks appear of a proper quality but could be less expensive actually; by the volume of the brick body, it works out less than 2 standard firebricks, and the 6″ size (1-1.2″ extra) isn’t particularly extra beneficial unless you were making a production oven of course which you would pay off quickly AND the oven’s efficiency or practicality would make live much happier by these means. I hope I could help you with this info.

    By Rado — Permalink

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