Tuesday, 21 January 2014

Building a wood fired oven - dome bricks started

The first few dome bricks for our wood fired bread and pizza oven have now been set.  It is more usual for this to be done using a form for a single brick width so that.  The single brick width dome technique as described by Alan Scott in the book the Bread Builders, which I discussed in a blog post here, involves moving the form work after each brick arch has been set.  I have decided to make a full length form-work so that each course of dome bricks can be offset by half a brick for improved strength and resistance to cracking, it also allows me to build the entire dome before removing the support without worrying about it collapsing.  As I am racing the cold weather that is coming in a couple of days, and due to the lot temperatures here, the mortar is going off very slowly, so I need the dome finished fast and supported until it is fully finished.  

Form-work positioned in the oven
The form-work is adjusted to the correct height using four stacks of bricks and two quick substantial pieces of wood, cut the the correct length of the form.  The form has been trimmed to be just small enough to be removed through the oven mouth.

Angled dome support bricks
The bricks at the top of the side wall have been angled to maximise contact with the first dome brick.

First 4 rows of dome bricks
When laying the first 4 rows of dome bricks, some of the bricks did not want to stay in the correct position, so small pieces of fire brick have been wedged in the tapered gap between dome bricks.  Only a small amount of refractory mortar has been used here,  where the tapered gap become wider than about 6 mm, it has been left unfilled.  This will later be backfilled with a different mix of mortar.

Dome bricks supported by form-work
Care has to be taken in order to make the corners of dome bricks meet as closely as possible.  The bricks should fit together with almost no mortar separating them.  This is not possible in reality  due to slight inconsistencies in brick shapes and sizes.  
The weather here is looking like getting very cold in a couple of days time, so I need to get this dome finished, the supports removed and a heater under the dome before I get problems of the mortar freezing and destroying all our hard work.