Need advise for oven floor clay oven

[hotstuff]

Hi oven lovers,

I have recently embarked on building a clay/clob oven in the back garden (using powered clay).

I have been using the e-book guide created by Simon off clayoven.wordpress website.

But the plinth design we are doing is from another site, basically what we have done is use celron blokes and 4 paving stones (35mm thick) at the top for a 120x120mm overall size.

Here is what it looks like:



We then placed some bricks to create a border around the plinth top:



This is where we have so far gotten today.(Monday 27th July)

The plan is to put a layer of sand down and set the London bricks to become flush with the brick border creating the oven floor.

Right my question is: before doing this step will the sand layer and the London bricks be enough?

I'm worried than when it's all done the paving stones my crack and break under the heat.

Advise would be much appreciated

[oblertone]

Once it's done, it's done and retro fitting underfloor insulation is practically impossible, so I'd recommend an insulation layer under your bricks. I used 25mm vermiculite board which is readily available in large sheets and provides a flat surface for your bricks.

[hotstuff]

Jul 28, 2015 0:26:33 GMT oblertone said:

Once it's done, it's done and retro fitting underfloor insulation is practically impossible, so I'd recommend an insulation layer under your bricks. I used 25mm vermiculite board which is readily available in large sheets and provides a flat surface for your bricks.

Hi, thanks for the reply

I'm kinda on the edge of the budget now after buying the celron blocks and the clay (£114) and the 25mm vermiculite boards are £50!!

Is there any cheaper alternatives I could use?

[hotstuff]

We actually took back 10 Celron blocks we didn't use to B&Q would these have been ok to use for a insulation layer?

[hotstuff]

Is anyone on this forum?

[cannyfradock]

Hello Hotstuff....welcome to the forum.

In hindsight the 10 celcon blocks that you returned to the builders merchants would have been perfect for an insulation layer between your paving slabs and your brick hearth. How far are you in the build? If you are not too far into your build I would go and buy back the celcon blocks. You could even lay them flat and without mortar onto your slabs. They should come up to the same height as the border brick-on-edge that you have laid. The London brick can then be laid on top of the celcon blocks.

If you have already laid your hearth bricks .....will the slabs crack?.......more than likely not, but without an insulation layer between slabs and brick hearth you will need more wood to keep the heat in the hearth.

In any introduction at the top of the homepage i have tried to let people know that a little research...or looking at how other people have built their oven in the relative oven builds ......is your best friend!!....I have built perhaps 10 fire-brick Pompeii ovens and a couple dozen clay ovens now but the only oven that I built that doesn't work as good as it should is the pizza oven that now still stands in my back-yard....simply because I didn't do any research....that's why i created this forum so us wood-fired enthusiasts (in the UK) can learn off other members.

When all's said and done....they all work. If you don't manage to get the correct insulation layers under the hearth and over the dome, then it just means you may have to put a bit bit more wood on the fire to achieve the same results.

When you are building the dome, try to build it 2 layers. The first layer..about 3" thick puddle your clay with 2 parts sand to 1 part clay with water added if needed and the second 2" inch layer make the same cob but add lots of either hay "bits" or wood chip.....not sawdust, but perhaps the type of spoil that comes from a chain saw. This will create a layer of cob with many small voids in it. Any wood or hat will eventually burn out leaving a honeycomb effect in the second layer layer of cob. This will give the dome it's refractory quality, throwing the heat back into the dome. By using a thermal layer between slab and hearth will give the same effect.

Don't get too despondent if your questions don't get a response. Forums are often like that.....some get lots of response, others, not. You can always reply to your own question with "Bump" which will put it back into "most recent posts".....if you don't get an answer to an important question you can always drop me a PM.

All the best with your build.

Terry

[hotstuff]

Jul 28, 2015 18:52:00 GMT cannyfradock said:

Hello Hotstuff....welcome to the forum.

In hindsight the 10 celcon blocks that you returned to the builders merchants would have been perfect for an insulation layer between your paving slabs and your brick hearth. How far are you in the build? If you are not too far into your build I would go and buy back the celcon blocks. You could even lay them flat and without mortar onto your slabs. They should come up to the same height as the border brick-on-edge that you have laid. The London brick can then be laid on top of the celcon blocks.

If you have already laid your hearth bricks .....will the slabs crack?.......more than likely not, but without an insulation layer between slabs and brick hearth you will need more wood to keep the heat in the hearth.

In any introduction at the top of the homepage i have tried to let people know that a little research...or looking at how other people have built their oven in the relative oven builds ......is your best friend!!....I have built perhaps 10 fire-brick Pompeii ovens and a couple dozen clay ovens now but the only oven that I built that doesn't work as good as it should is the pizza oven that now still stands in my back-yard....simply because I didn't do any research....that's why i created this forum so us wood-fired enthusiasts (in the UK) can learn off other members.

When all's said and done....they all work. If you don't manage to get the correct insulation layers under the hearth and over the dome, then it just means you may have to put a bit bit more wood on the fire to achieve the same results.

When you are building the dome, try to build it 2 layers. The first layer..about 3" thick puddle your clay with 2 parts sand to 1 part clay with water added if needed and the second 2" inch layer make the same cob but add lots of either hay "bits" or wood chip.....not sawdust, but perhaps the type of spoil that comes from a chain saw. This will create a layer of cob with many small voids in it. Any wood or hat will eventually burn out leaving a honeycomb effect in the second layer layer of cob. This will give the dome it's refractory quality, throwing the heat back into the dome. By using a thermal layer between slab and hearth will give the same effect.

Don't get too despondent if your questions don't get a response. Forums are often like that.....some get lots of response, others, not. You can always reply to your own question with "Bump" which will put it back into "most recent posts".....if you don't get an answer to an important question you can always drop me a PM.

All the best with your build.

Terry

Hi Terry!

Thanks for reply

I've spent literally all day (at work shhh) researching what to do I trawled through and searched the old forum which redirects to this one by the way.

The old site had loads of pages of information which I've searched through and come to the conclusion that yes I had the awnser already and took back the blocks haha d'oh!

I've also learnt that fire bricks are amazingly expensive even more so when delivery is added to them! So I'm trying to find an alternative if possible??

I went and bought NEW London bricks also from B&Q for the oven floor thinking new is better but I have since also learnt they apparently are not good as using the old school bricks (reclaimed) luckily I only bought 15 which was like £7.50. Not sure if I should risk using them.

I haven't done anything today yet today I've only been researching about insulation for the slabs.

So I'm going to go back and get 4 celron blocks! And lay them flat as you said on top of the slabs hoping that the insulation issue is solved. I will post progress pics if that's ok?

The way I'm bulding the layers Terry is doing the sand former then the first layer will be powdered clay and sand not sure what ratios yet I might have to test different ones.

Second layer - clay and sand mixed with wood shavings.

I was going to also do a 3rd layer which will be sand and clay again.

Hope this sounds right I'm following the guild on clayoven site I mentioned on the OP.

Thanks again Terry for replying and giving me feedback

[hotstuff]

Right going to get some celron blocks today.

We went and got some reclaimed bricks from the local place £1.25 a brick! Cheaper than the fire bricks I suppose lol.

We had 3 breeze blocks laying about in the harden will these be ok to use in addition to the celron blokes? We actually exposed some to a open flame for 10 mins to see what happend....it retains the heat nicely so I'm thinking it should be fine.

Here is some pics showing the re jig.

[hotstuff]

Picked up some additional celcon blocks last night after work also grabbing some more reclaimed bricks this morning to fill the oven base floor (80cm) then on the outside of the oven floor using normal London bricks we bought as I think these won't be getting the heat as much as the oven floor does so this should be ok right?

[hotstuff]

Talking to my self again haha!





I have now lined the heath with celcon blocks/breeze blocks.

Right need some advice if anyone can help me:


1) What should I do to fix the reclaimed bricks down? or do even need too? would a layer of thin slayer suffice?

2) I'm using powdered clay so I'm not sure what ratio to use, I was going to make up some sample bricks with 5:1 4:1 3:1 3:2 and see how they turn out. But there's not much info on the net using powdered clay.

3) Regarding the entrance arch I'll be using the newer London bricks I picked up would these ok to use or would the heat crack these too? also to fix them together would normal cement be ok? or should i use the clay mix?

Thanks in advanced

[rivergirl]

I actually went the bottle ,sand route for insulating my base, I am saving bottles and jars to do the same for this build. You are right about how expensive the bricks are here! I bought mine in France for half the cost. As Terry said please don't lose heart if no one answers! We maybe all in the garden playing with our ovens!

[daggle]

Hi Hotstuff

I know it can be quite frustrating to ask questions and not get answers straight away especially in the middle of a build! To fix my oven floor bricks I used a mix 50/50 of builders sand and fireclay with enough water to make it into a sticky mess! Trowelled it on with a 10mm notched trowel doing about 2-3 bricks worth at a time. It wasn't easy to work with but my bricks are nicely leveled and it is possible to break the bond if you need to get one out.

My fireclay was sourced through MKM and when it arrived in tied up black bin bags I was highly skeptical, it also had a hand written sticker on it saying Ground Fireclay which also didn't sound right! However when mixed with water it turns quicksharp into a lovely smooth dark grey clay and when incorporated into my homebrew mix gives an earthy workability so at the moment I'm quite happy :-) I suppose the final test will come once I get it fired up!!

Good luck with the rest of your build.
Cheers
Daggle

[hotstuff]

Jul 31, 2015 13:09:55 GMT rivergirl said:

I actually went the bottle ,sand route for insulating my base, I am saving bottles and jars to do the same for this build. You are right about how expensive the bricks are here! I bought mine in France for half the cost. As Terry said please don't lose heart if no one answers! We maybe all in the garden playing with our ovens!

Hi Rivergirl!

I been reading through some of your threads and recipes

The Celcon bricks are not that bad there £1.78 each it's these damn Fire bricks that's a pricey! i had a budget of around £200-£250 for this build and iv'e spent around £225 so far and don't want to incur any more expense now. the bulk of the expense was the 175kg of powdered clay but I could not source and clay from anywhere else and I was getting to the point of sod it I'll buy some! that was £114 and I went to go and pick that up other wise delivery was extra £40

I'm just hoping the reclaimed clay bricks are ok for my oven floor and iv'e not made a mistake not spending another £60-£80 on fire bricks. RANT OVER lol...

It's nice to meet you and thanks for dropping into my thread

p.s. I could not find your build on this site do you have a link?

[hotstuff]

Jul 31, 2015 13:35:19 GMT daggle said:

Hi Hotstuff

I know it can be quite frustrating to ask questions and not get answers straight away especially in the middle of a build! To fix my oven floor bricks I used a mix 50/50 of builders sand and fireclay with enough water to make it into a sticky mess! Trowelled it on with a 10mm notched trowel doing about 2-3 bricks worth at a time. It wasn't easy to work with but my bricks are nicely leveled and it is possible to break the bond if you need to get one out.

My fireclay was sourced through MKM and when it arrived in tied up black bin bags I was highly skeptical, it also had a hand written sticker on it saying Ground Fireclay which also didn't sound right! However when mixed with water it turns quicksharp into a lovely smooth dark grey clay and when incorporated into my homebrew mix gives an earthy workability so at the moment I'm quite happy :-) I suppose the final test will come once I get it fired up!!

Good luck with the rest of your build.
Cheers
Daggle

Hi Daggle

Thanks for dropping in too!

What is fire clay lol is it just a fancy name for normal clay?

I have Ball powdered clay from www.claycellar.co.uk/clay/powdered-clay/product/226-ball-clay

So your saying use some of the powdered clay and sand to make a "bedding" for the oven floor (reclaimed bricks) and set them onto that?

[daggle]

I thought I'd replied already from work!! The company that sold you the ball clay also sell fireclay so maybe they could tell you the difference sorry but I can't!!

Yes I just mixed equal quantities of clay and sand with enough water to make it sticky and then got messy!!!