New build for first timer...

[dellboy78]

Hi,
I am about to embark on my first clay oven. I have a position near the house where I want to put it and would appreciate some feedback from those more knowledgeable than me. I have an area of raised patio around 1470x1160 in size, in the corner of our patio area. I don’t know what is underneath it but I can’t decide whether to build my block and lintel base directly on top of it, or rip it up and cast a concrete slab to build on. I have added some photos to show what I mean and would be grateful for any ideas?

[devontiger]

Just an idea dell, I would build a row of blocks (dry build) along the rear. (Double hole type blocks very sturdy).
With three rows coming out, one on each wall side, one centre.
This will allow you to position the oven anywhere along the wall, also giving some flat work space.
Cast your own top with reinforced cement.

Are there any cracks or uneven surface on the base?
If not I would build off the crazy base.

Later on you could build yourself a gazebo over the area, to keep you dry when its raining.

Anyway, Welcome to the site dellboy, where all things are Pizza.

DT
Ps. The blocks wont move, unless you give them a good kicking. And lay them as you would a brick, by overlapping them.

[dellboy78]

Thanks for the response. That is pretty much the kind of thing I had in mind. When you say ‘dry build’ do you mean don’t cement the blocks together? Knowing my luck it would all collapse!
The crazy paving seems to be quite sound. Maybe I will get a bit closer down to see if I can spot anything iffy.

[devontiger]

[downunderdave]

Hi Delroy,
Unless you break up the slab under the crazy paving, you really have no idea how thick it is or whether it contains steel reinforcing. But if you get a decent electro hammer drill with say an 8 mm bit and drill a hole through it you can tell how thick it is at least. When the bit breaks through the bottom measure the drill bit length embedded. This will be the thickness of the slab, although won’t tell you if it’s reinforced. It’s a lot of work demolishing a slab and you’ll probably get away with not replacing it, but a builder probably would.
When dry stacking concrete blocks you should glue them together where they meet with masonry adhesive, it’s surprisingly strong and if you then fill every other core it makes a strong support.
I’m concerned about the missing row of bricks at around shoulder height on your wall. I’d be filling it before proceeding.
Hope this helps.
Dave

[crammy]

i used the hollow concrete blocks for my corner build. I did put a rebar in mine and filled the holes up with concrete. i then bent the tops over which allowed me to weld more rebar in for the slab. i shall try and find a picture for you if i have one. it may be on my old phone

[dellboy78]

I have had another look at the paving out there, I’ve not drilled through it yet but have checked it with a level and given it a tap all over with a hammer to see how solid it sounded. The back half and down the sides sounded fine, but towards the front and centre definitely sounded more ‘hollow’....it will not be easy breaking it out if I go that route, and I’m not sure how to cast a level slab when I only have access from the front!

Also the row of missing bricks is closer to waist height. I think this used to be a bbq area in the past so that is where the bbq used to be. Hopefully it will just about be hidden once I’ve finished, or if not I will find a way to fill it in.

[oblertone]

Sounds like the 'hollow' area will be where a wood store entry would be on a more conventional build, i.e. Not load bearing so I'd be tempted to utilise that and not break it out. One other point to consider is the small step at the front as this will affect the level of the cooking floor when the oven is in use; that floor needs to be around the elbow height of the primary user, otherwise it becomes uncomfortable.

I'd be tempted to make best use of the existing structure and place pre-stressed lintels across the gap using the wall at one side and a block wall on the other. Then a few 'council' paving slabs to give a flat deck on which to build your WFO. Just a thought.

[dellboy78]

I quite like the sound of that last idea! I must admit the thought of breaking it all out and starting from scratch is not a good one. I did want a wood storage space underneath and I think lintels and pavers will be easier than casting a base for the oven.....

Thanks again guys for all the replies so far. I am sure I will have more questions imminently...

[dellboy78]

Just doing some sums and trying to get a materials list together, so I want to work out the height my block wall needs to be so that I end up with the right finished floor level. Starting from the top then, what thickness of firebrick is recommended for the hearth in order to create a good thermal mass?

[truckcab79]

Pretty sure they’re a standard size, unless you’re going to use heater storage bricks or something that’s not the norm. In which case I’d source them first and then measure off that. 

shop.vitcas.com/firebricks-230x114x64mm-6-p-asp.html?gclid=CL_5x4TB1eICFec10wodPc4E6A

[dellboy78]

Thanks for the link mate. They do seem to have a range of thicknesses from 32mm up to 76mm. They all seem to be the same price though for some reason so I guess the thicker the better?

[dellboy78]

So, the base is coming along at last, I have put some photos below. I am going to have around 153mm give or take for my insulating layer and fire bricks. I am still undecided on what to use as insulation and what thickness of fire brick to use. Any suggestions?