Derbyshire New Build

[kinley]

A two-stage report on a long planned build. Phase one happened last year as a redevelopment of a patch of waste ground. Half a dozen conifers and 5 tonnes of soil were removed first. Tree root removal courtesy of tractor power. First part was to build a double wall and clear the site.







Built the top section of the wall first.






Then laid the slab. Re-enforcing looks flimsy but there was a stack of 30cm GSB followed by 30cm of old concrete 2'x3' council slabs. Not going anywhere.











Laid slabs and planted the wall.

[kinley]

Next job was the base skeleton a week later. This only took a few hours and was most satisfying after the toil of shovelling soil.








While the mortar cured I rendered the wall, finished the slabs and added angle bead to the wall.






I saw no reason the arches couldn't be a structural part of the base. Roman arches in yellow suited the limestone of the surrounding countryside more than the red birch I personally would have preferred.






Cracking on with the hearth, 10cm concrete on Aquapanel. Quick and easy.

[kinley]

I used K-rend for the wall and base and was both delighted with the ease of use and effect.







Bought some 22mm granite off ebay for peanuts in exactly the size I wanted, 1000x1200mm with the corners removed to stop children banging their heads.







K-rend with a scratch coat left a quite wonderful effect.






And that was that. A dark NW facing part of the garden transformed into what now gets referred to as the piazza,

[kinley]

Winter came. No problems with the K-rend which survived but no building of the oven took place. I did, however, turn another waste patch into a garden room with wood burner (also know as man cave) beside an artificial stream. Not a wasted winter by any means and the sound of running water next to the oven is very pleasant!







However I am really struggling for time this year and set myself the unlikely task of an evening-only build in 2 weeks. Evening 1 I got the flood laid on 50mm calsil.








Evening 2 for the soldier course and the first row laid. Soldiers are not mortared to the floor. Using the classic home brew of 3:1:1:1.







Evening 3 I was on the door. This was my first significant compromise. I looked at the more square door design but felt that lateral buttressing would be required. As I was trying to make the whole structure as compact and unobtrusive as possible the round arch would be slimmer as well as mirroring the arch below. Secondly I did not have the time to spent cutting every brick. Instead the entrance narrows by 15mm allowing the door to have a snug fit, avoiding the need to cut a lip. This I was able to re-use the forms from building the arches in the base.

[kinley]

Evening 4 allowed the transition (this was made up as I went along and in the end very simple with the IT). With the completion of the second part of the entrance the chimney (a single skin seconds from ebay) could be placed. More on chimney design later.






On evening 5 the dome was completed using a simple sand form and slightly looser mortar. I used a combination of 64mm and 25mm bricks to get good brick contact then just filled the gaps with mortar.








Evening 6 saw the 50mm ceramic blanket in place. The chimney will be removable and I will fit a waterproof cover to the front of the oven preventing rain soaking bothchimney and calsil under the entrance bricks.






The the dreaded vermiculite. If I'm really honest I'm not sure what the fuss is! I made a form similar to a design from a previous thread and rattled around the first layer in an hour. I mixed about 6:1 with 1 part lime and added enough water until it started to get a little sticky.






The simple form I used: 2 minutes with a jig saw and some cardboard.

[kinley]

Evening 7 saw the next layer of vermicrete applied (another hour only) and evening 8 had it finished off. In the end it went on about 125mm rather than the planned 100mm and I used 5.5 bags. Within 2 days the vermicrete was solid.






I'm disappointed with the entrance arch which in neither symmetrical not even. My mistake was reusing the forms I have used on quite a few other projects as well as they had deformed. I'm not bothered enough to rebuild it though.

So it is possible to throw a dome up in 7 days. The finish of the dome is, however, far from pretty. Getting inside to tidy the pointing is simply not possible for a heavyweight rower.






Following a week to allow mortar curing ti was time for the first fire. Bang on 250C and a real 'moment'!






Second curing fire last night, hitting 250C on the floor and 450C in the dome. I know this is too much but the dome heated very, very quickly. The soot burned off nicely and no cracks so far.






The chimney design worked well with almost no smoke coming through the arch. I went through all the threads on this forum and noted that wide (side to side), narrow (front to back) chimneys had the least soot staining on the fort arch. This photo confirms the chimney efficiency. 

[kinley]

So early days but very happy with progress. I have posted because, just as I learned lots from the thread, I would like to help others build too. I love the beautiful builds on this forum but knew I would never have the time to complete such a project. I hope my thread showed that a very quick build can be achieved and that, while not pretty, it seems to work well. Some other tips from the build.

Use an angle bracket on the end of the IT. I just used a simple plank and as a result lost 5cm from the dome height. This means the door:dome ratio is 74%, supposedly too much. However I was hitting 450C in a 'wet' oven with a medium fire in 45 minutes so I'm not sure it's that critical. I would only need to lower the door by 3.5cm to get 63% and I'm not convinced this would make a great difference.

Cover the flood with cardboard as mortar is a bugger to remove from firebrick.

A cheap angle grinder and cheap cutting discs were fine. Cut gently and you can cut 5 or more bricks with one disc. I have a sliding mitre with a diamond blade and never saw the need to get it out. Cutting outside, I had no problem with dust so didn't soak bricks. I suspect this is why the dome heats so quickly (as well as 175mm insulation).

Make the home brew mortar less firm than house brick mortar as firebricks really soak up water.

Make the chimney opening wide and shallow.

The transition is easy with a round arch. Simply cut the back off the brick along a line guided by the IT and repeat across the arch.

A 36" internal oven isn't that big and I certainly wouldn't want a smaller oven.

The materials list on FornoBravo is way out. I used 135 64mm bricks, 9 25mm bricks, 3x 1000x500 calsil boards (with enough for the door) and one 3.6m 50mm blanket (4m would have been better) and one bag of fireclay.

Single skin chimney works OK if you oversize the chimney hole by 3-5mm. It expands quickly to fill the gap and doesn't leak.

Don't underestimate how much work the base and hearth are. Probably 75% of the build time was spend on these and the dome pretty quick.

Buy, borrow or hire a cement mixer, especially for the base and hearth.

Most importantly you can make the project and easy or difficult as you like. This was the first thing I have ever build and my DIY skills are basic. Take the plunge - you'll enjoy the process and I suspect the result even more.

[thetrev]

HI,

Great photos and write up,

can I ask a couple of questions, did you used a wedge or angle cut the bricks on the first row and from the photos did you use mostly half bricks on the wall?

thanks

Trev

[kinley]

I used half bricks for the soldiers, laid straight on to the floor. For the first row I laid the mortar onto the soldiers, used the IT to position it, couple of taps then left the IT in place to hold the position. There was no need for wedges as the mortar set within the time it took to get the next half brick into position.

[kinley]

First full firing went very well. Got the floor up to temperature in 2 hours.







First pizza was a beauty!







A veritable production line followed thereafter.






I had no problem keeping the floor at c385C. This seemed to be the 'natural' temperature regardless of how much wood was burning. I put the door on with the temperature gauge showing 350C. The following morning the oven was 250C so some bread went in. The children got to it before I got the camera...


 


By mid afternoon the oven was still at 220C so I took the door off for an hour to get it down to 190C then put this in.





This morning we are still at 130C so the insulation seems to be working. I'll fire it up at least once more before rendering. Overall impressions are extremely good. Pizzas were far better than I'd hoped for and with some organisation a couple of days cooking can be achieved (bread, baking etc in addition to roasts). Not had any problems with the rather rough interior although I wonder if the oven would heat faster if the door was slightly lower. I see a fine summer (and winter) ahead!

[kinley]

Finally finished. Allowed 3 months to fully dry with 4 firings along the way. Put on a scratch coat with sika proof followed by K-rend.






Used porcelain floor tiles for the surround, placed prior to the waterproofing layers. Essential for beer placement.






Gave some thought to keeping it dry. The flue is removable and rain would easily soak through the entrance arch floor bricks into the calsil board. I initially though of covering the whole front with a tarpaulin but my wife pointed out that this would hide what is quite an attractive construct and look pretty ugly. So I came up with two separate covers which have proven their worth in some recent torrential downpours.






Overall I'm delighted with the function. I can get the floor to 385C in an hour, have a 600C temperature difference (630-30) from inside the dome to out and after 36 hours the oven is still at 150C having cooked two roast dinners (neighbours as well as ours) and two loaves of bread. I thought I might only use it a few times a year but given how quickly we can get it going, once a month seems to be the norm.

[oblertone]

Fantastic build, thank you for sharing.