How many bricks?

[username]

Hi, I'm building an oven within an old coal shed. I've got an area of very nearly 1 metre square (somewhere around 39" square in old money) to play with. Approximately how many bricks will I need for a dome oven of this size?

[dmun]

Re: How many bricks?

That's a really small dome: 39 minus four (two inches of refractory blanket per side) minus eight (thickness of two half bricks) is a twenty six inch (66cm) oven with a thirteen inch height. What are you planning to cook in this? Could you cut into one of the sides of the shed to get you up to at least thirty?

[username]

Re: How many bricks?

Sorry dmun, I could have explained myself a little better there.

The coal shed I'm using is an old stone building about 5 foot high and with walls maybe 8 to 10 inches thick. The inside floor space is roughly 1 metre square - more precisely, 40 inches by 39.

There is a door on one side that's about 2 foot wide. The entrance that this door forms thus adds an extra 24" * 8" to the 'square' floor space. Naturally this door way will be where I'll build the mouth of the oven.

I could probably hack away a little of the side walls to enable a slightly bigger diameter dome, maybe a few inches either side just where the dome touches it - shouldn't be too difficult with stone cutter.

The oven's going to be used for pizza and bread.

[dmun]

Re: How many bricks?

James videos of the new miniature oven notwithstanding, I think it's really limiting to cook pizza in that size of oven. I have a thirty-six inch oven (91cm) and think it's about the right size. There's room for a fire, and room to move the pizza around to get different temperatures: It tends to be hotter in the back.

As to your brick count question, here is the brick count thread I made for the 36;

http://www.fornobravo.com/forum/f8/3...ayout-171.html

An oven with half the floor area will no doubt take fewer bricks.

[Rastys]

Re: How many bricks?

Hi Username,
with a construction having those dimensions, I would seriously look at demolishing the top section (carefully) to provide your base/foundation.
I would then pour a concrete slab, insulate it and then build a 40 to 42" oven that will meet your needs
You might also be able to re-use some or most of your demolished materials (bricks and stone) within your dome and facia/chimney void.
A photo or 2 would be handy to see any potential problems.
I used around 160 standard sized house red bricks for mt 1000mm diameter oven

Rastys

[Frances]

Re: How many bricks?

I'd like to see a picture of the shed, too. How old is old? Could be very cool, as in a sin to knock down....

You'll have to make really good use of the space you have though: Take a bit off the walls inside, maybe reduce the thickness of the oven where its closest to the wall, use the refactory blanket for insulation, build the oven with a slightly oval shape (check out SpringJim's Benjamia oven). Should work somehow.

Don't listen to George btw... I like your username. Very distinctive.

[username]

Re: How many bricks?

I'm afraid that demolishing or part demolishing the shed isn't really an option. It shares a concrete roof with a neighbour's shed and one wall is also supporting a nice old climbing plant

Though, having looked more closely at it, the walls are a foot thick and I reckon it wouldn't be too hard to remove 6 inches or so from the sides. That should allow for an oven with internal diameter approaching 40" - I think?

I'll post a photo when I find a working camera.

[dmun]

Re: How many bricks?

You don't even need to cut the whole side, just a crescent out of each side should do the job. I don't know what kind of stone it is, but a diamond blade in an angle grinder should make short work of most things softer than quartz.

[PeterW]

Re: How many bricks?

I've got a smaller oven and I would say don't bother cutting into the walls. If you can get 1" of mineral insulation between the bricks that touch the back and sides then its plenty. Also, using those bricks round the edges closest on their 'thin' side ie 2.5" vs 4" then you will get 32" diameter, plenty to do what you want to do. Its all about how much you want to use it, and how much space you have to store wood - and big ovens need lots of wood..!

Are you planning on leaving the old door in place so it doesn't look like an oven when not in use..?

I would be inclined to drill a hole with a holesaw in the roof 5" in diameter to take the chimney, and another couple slightly smaller so you can brick the front up as you finish the build and then fill the rest of the void with vermiculite through the roof.

I wish I'd had that sort of option when I started, but I'm really happy with what I've got now !

Post a couple of photos so we know what you've got, and we will try to help. The was a thread about UK suppliers a while back, PM me if you need help..!

Cheers

Peter

[username]

Re: How many bricks?

Well here's some photos. I had already poured the concrete slab before I discovered this website - luckily I only got that far. As you can see, I've started widening the inside of the shed. I think I'll be able to find room for a 50" or maybe even 52" diameter base. I still need to remove a little more and backpoint the holes that I have made to strengthen them.

[dmun]

Re: How many bricks?

Hey, that's great! I love your stone shed reuse!

[username]

Re: How many bricks?

So, the next thing I need to do is buy a load of refractory materials. As it's a fair trek over to the suppliers I'd really like to get everything I need in one go.

Besides the bricks, what other refractory materials will I need and in what quantities? What do I require for the insulating layer below the hearth bricks and for the dome? Do I need refractory cement to mortar the dome bricks and how much? I've heard that a layer of fireclay should be used to bed the hearth bricks - how much will I need? Is there anything else that I've missed?

Thanks

[dmun]

Re: How many bricks?

Under the floor you need one of two things: a four inch layer of vermiculite (or perlite) concrete, or a two inch layer of refractory insulation board. The insulating concrete leaves a rough surface, and you need a layer to level it, which is a mix of fireclay and sand. You need only enough to level the surface. If you go with the insulating board, it's mostly flat enough to lay the bricks directly down on it without mortar or leveling layer.

As far as mortar, your choice is a commercial dry refractory mortar mix (I don't know what your brands are in the UK). We are warned off the premixed wet stuff in tubs. It's a bit pricey. You can also make your own mortar with sand, fireclay, portland, and lime.

Your dome insulation can be a refractory mineral wool blanket or insulating concrete, or a mixture or the two. Since you are building in a closed building, you could also fill the cavity with loose vermiculite, but be warned, the stuff has a tendency to leak out of the smallest opening. You can create dams in the corners with cement board to reduce the amount of insulation needed. In that enclosed space my guess is that you are going to run out of room to work really quickly.

The only thing you need is to think about your flue, but that's more of a brickyard item than a refractory dealer one.

[username]

Re: How many bricks?

Thanks dmun, that's answered a load of questions. One thing - what ratio should I mix the perlite/vermiculite concrete? Does the p/v just replace the ballast in the mix? Similarly, if I use the lime/sand/portland mortar (I am a cheapskate), what ratios would be used there?

[dmun]

Re: How many bricks?

I'm off to do something right now, but you might benefit from downloading the pompeii instructions, which covers these things.

Quickly, yes, the vermiculite is the aggregate in the vermiculite concrete. I never used the home brew mortar, so I couldn't give you the ratios without looking it up.

This might be the link:

http://www.fornobravo.com/forum/f6/h...rimer-914.html