East Lothian Build

[MikeyC]

Hi All,

Long time reader, first time poster. I thought I'd share my build with you all below.

The idea of constructing my own outdoor pizza oven was something that I had been talking about amongst family for many years, but unfortunately at the time I didn't have my own garden to put one in. When my father in law presented me with the oppertunity to build one on his land some 4-5 years ago, I somehow never found the time to take him up on the oppertunity. It then became a bit of a running joke in the family of when actually I'd ever get round to building one. Truthfully, I was a little apprehensive of the challenge it might present having very much only opened a tool box to hang a picture or two on a wall. The worry I'd end up with a half finished garden folly, or the world's most expensive concrete dog kennel was always there. When finally last year we decided to give up city centre flat living (the arrival of kids), and bought a house with a garden big enough to put one in, I was left with no excuse but to crack on and give this project a right good go. Paternity leave (because what else really do you have to do during such a time?) earlier this year presented me with two weeks off work, in a period of good weather, at the end of March, I decided to put a spade in the ground (very much with the Mrs MikeyC's blessing) and get going with what would turn out to be one of the best and most fun projects I've committed myself to in recent years. Below is a small photo diary of the build; a 43" dia. Pompei brick oven. I hope it provides useful insight and encouragement to others.

[MikeyC]

I started researching around 5 years ago the idea of building my own oven. I started off looking at various websites (this one; which is a superb starting point for anyone, Forno Bravo and various other blog pages out there on the web) to get as much information as I could to establish if realistically I could do it on my own. I bought Russell Jeavons book 'Your Brick Oven' and used this as a starting point, and like many on here I followed a great deal the free downloaded plans for a Pompei style oven from Forno Bravo web page (American site which was really useful).  I did however veer off piste on many occasions from the FB plans; in particular with oven base/plinth construction, as I found that they over cooked the structural reinforcement recommendations and also I wanted my base/plinth to be a little more compact - really the base is one the areas you can be the most creative in.

The Ground Slab:

I was aiming for a 1.5m x 1.5m base, with a 1.1m / 43" dia brick oven on top. Once I finally decided which spot in the garden it would sit, I set about pegging it out and getting digging - though I had a 7ft well establish bush to remove and root out first - boy was that tough going by hand!

I reinforced the slab with some salvaged concrete reinforced lintels and spread the concrete mix around. This help save on the amount of concrete mixing I had to do. I did the mixing by hand. By the end of the project I became very attached to my 1.2m x 1.2m mixing board and shovel with the amount of mixing I would do!

PS I hummed and hawed about laying a DPM under the slab prior to pouring however I opted not too and so far I haven't regretted doing so, but I'll get onto to that later on in further posts. 

[MikeyC]

The Base/Oven Plinth:

I opted to use 140 x 215 x 440mm block work in lieu of the hollow core blocks specified in the FB plans, set out 3 x block lengths + 1 block width for each side (see photos below). I decided on a central cross wall to support the slab above on, and filled the void at the back with sand, ballast, broken up concrete blocks (any masonry off cuts and rubble I could find) up to the under side of oven slab level. The front  half/void would be used as a log store and was left unfilled The Log store would be fronted with a brick arch (photos to follow). I started of with the intention of building 4 x block high but half way through I decided this would be too high,as there still a 150mm slab plus the height of a fire brick to go on top (it would have been around/ just over 1.2m in height to the oven slab with mortar joints taken into account). Instead I went with 3 x block high with 1no. Brick and then 150mm slab on top, finally with fire brick as oven base.  this brought the overall height to pizza oven base (what the pizzas would cook on to just under 1.1m). The slab would then sit Inbetween the  perimeter block walls on three sides, rather than on top, with its front end resting on piers and supported as well off the central wall and back infill build up. This allowed me to use the perimeter side block walls as shuttering to pour the slab up against meaning I only had to form  slab formwork on one edge (front end), see below.

*I had a little helper at the crucial central wall setting out stage!

[MikeyC]

The Upper Slab:

I cobbled together formwork and support from off cuts of timber I had, and used some left over laminate timber floor boards from the house I had stored in the garage. The laminate timber floor boards where really useful as the tongue and groove edge allowed me to click these easily together to form the base to pour on, and then allowed for easy removal once slab was set. The gaps around the formwork where taped up with masking tape (later removed once slab set). I was kindly given some metal rods (approx 5-6mm in diameter) which I cut to size and used as reinforcement for the upper slab. These I propped up on quarter bricks and tied together with metal plant ties (the bricks can still be seen in the u/s of slab if you  stick your head into the log store and look up). I cut the rods with approx 1.5" short of slab edge. The slab mix was standard 1:2:4 ratio (1 part Portland cement, 2 part sand, 4 part coarse aggragate), and was poured to 100mm thickness. I opted to insulated the slab with  50mm Vermicrete Mix (1:5 Ratio). Overall slab thickness 150mm.

Note; In building the slab up against the block walls on three sides left me with having my oven extending beyond the Insulated slab line and onto the block walls (see photos) This meant that a fraction of the oven brick walls would sit on an un-insulated wall head. How much this would effect the oven's performance was unknown at that stage, though having been operating the oven now for 3 months I haven't seen this be an Issue to the overall oven performance.

[MikeyC]

The Oven Base:

I read many suggestions on what type of brick to use and opted with opinion on using fire brick on the oven base, however went against opinion and used reclaimed imperial sized, salvaged solid red bricks for the oven dome. I managed to buy 265 reclaimed bricks for £100; that's £0.38 per brick, which is approx a quarter of the cost of buying new fire bricks - opinion is with using fire bricks for every part of the build, as they apparently perform/retain heat better and are less prone to spalding under high temperatures. Standard brick is fired under temperatures that exceed anything your pizza oven will ever get to, so I didn't really see this as an issue. As I was aiming to build my oven to as tight, and controlled a budget as I could manage, I went with the reclaimed option. The Forno Bravo team do note that if your only option is to build an oven out of standard solid red bricks or not at have an oven at all, then build it out of red bricks! 

Once the slab and vermicrete topping had set I started to chalk up the outline of my oven plan and also set out the oven entrance door/arch position. From there I started to lay out the fire bricks across the template base in a herringbone pattern (recommended so your oven peel doesn't catch on the brick edge), before again marking out/templating the oven dome inner wall outline on the bricks, and finally cutting to size. I opted to cut the oven base bricks to fit within (recess into) the oven dome walls. Opting to do this is more time consuming. The brick cutting is laborious and I had one or two bricks which split wrongly/became wasted brick. Allow for a surplus of bricks when ordering. I cut the bricks with a 4" angle grinder to begin with, then managed to borrow a 9" grinder which was more effective and made the job a lot easier.  Fire brick is very brittle and cracks up far easier on finer/thinner cuts.

Once I had the fire bricks all cut I laid these out on the ground temporarily as I set about spread in a fire/heat resistant paste across the slab before again setting the oven base fire bricks out.

[james9]

Mikey, what are you using to cut your bricks? cuts look good.

[MikeyC]

Hi James,

Thanks for the kind words. The photos don't say how laborious this stage actually is! Definitely one of the more trickier parts of the project. I started to cut the bricks with a 4.5" (115mm) bladed angle grinder, cutting right around the brick then finishing the central part off with a roughened brick bolster - due to the grinder blade's radius not being big enough to cut through the entire brick thickness. I found using the bolster on the fire brick quite difficult around the thinner, more detailed cuts; I.e. around the oven entrance and where small section of bricks where required on the curved perimeter. Fire brick is very hard and brittle and I had to do quite a few re-cuts in certain fiddlier areas. Well worth having spare brick stock! I was able to borrow a 9" angle grinder halfway through this task which could cut through the bricks in one slice. I'd recommend this, and to use a diamond cut masonry blade too, well worth the extra outlay against disposable blades; which reduce in diameter during usage and are generally not up task.

[MikeyC]

The Brick Dome:

With the base in place I set about cutting the 150 or so bricks required for the dome in half. I did this using a 4.5" angle grinder and brick bolster to finish off the central core of the brick - the grinder's blade radius was not big enough to cut right through the brick in one go. I was able to borrow a 9" grinder later on in the build and in hindsight I wished i'd opted for one of these instead of the 4.5" one I'd bought. I would recommend this to anyone in two minds. It  would have reduced the time of this part of the job considerably! Worth bearing in mind; cutting clay bricks creates immense amounts of red dust. I soaked the bricks in a wheelbarrow filled with water prior to cutting, but even wet bricks create plumes of dust. Position your cutting area in a part of your garden that is easy to tidy up afterwards, and certainly nowhere near your garden's lovely flower display! It took me a full weekend slot to cut the bricks.

I'd been looking forward to this stage, and had set aside a long weekend (4 days) to make headway on the dome. Low and behold the Scottish weather was torrential rain. I started the dome brickwork with a make shift temporary shelter and after one day decided to pickup a relatively cheap gazebo from B&Q to erect over the build - it cost £25 and was well worth the outlay; as it allowed me to continue working in the worst of the rain. 

The Indispensible Tool:

Like many I fabricated one of these from a few bits of timber and a spare timber gate hinge I had; see photos. The tool was really effective and I was able to use it right up until the last 3 courses. My dome height/radius was 21.5". 

[MikeyC]

Crowning the Dome:

As useful and effective as the Indispensible Tool is there comes a point where the mortar won't hold the brick, and gravity inevitably takes over. This started to happen around the 8th tier/row of bricks. It was time to create a temporary prop/base of sorts to help support the final crown of brickwork. I had read many suggestions on how to do this, and decided upon using a circular base fabricated from MDF, propped up on bricks and then topped with sand which I could rest the bricks on. I halved the timber board in two and fixed each half together again with some spare gate hinges I had. Hingeing the MDF board allowed me to fold it on itself and get it through the dome entrance arch and back out again - keep this in mind! 

Once the temporary prop and domed sand crown where in place I set about completing the brickwork dome. The key stone(s) can be seen in photos below. Once all the brick was in place I backfilled the gaps between with fire clay mortar mix and allowed it to set. I left it propped up in place for 5 days to allow the dome to set, and removed the prop work and sand the following weekend.

[chas]

Clearest demo I recal seeing of this tricky part of a build, and an interesting use of the commercial oven-build approach.

Chas

[Thomobigands]

Building a sand dome is what I did too and is a good way round the problem I think. Cleaning out the sand can be a pain, that's my only slight niggle. I had a circle of cardboard protecting they floor throughout the build though so that came in handy for catching the sand and not allowing too much to fall onto the final cooking floor surface.

[MikeyC]

Nov 8, 2017 6:25:04 GMT Thomobigands said:

Building a sand dome is what I did too and is a good way round the problem I think. Cleaning out the sand can be a pain, that's my only slight niggle. I had a circle of cardboard protecting they floor throughout the build though so that came in handy for catching the sand and not allowing too much to fall onto the final cooking floor surface.

Great tip Thomo. I used a metal bristled brush to  remove the sand left over on the oven base. I had cardboard under the supporting brickwork to protect my ovens fire brick base from getting scratched up. Sand, I found, will likely get below the cardboard line even with cardboard in place over your oven floor. Splitting the cardboard up/having it in sections in order to get it in and out of the oven front arch will leave gaps between the cardboard sections for it to fall between - you could maybe squash the template in place and then cut up with a stanley knife post capping? Some of the sand helped filll in the slightly larger gaps between the oven base brickwork and base perimeter edge....Great build by the way Thomo. Just finished reading your build thread - very well done!

[MikeyC]

The Outside Brick Arch and Chimney Flue:

On completion of the dome I tied it altogether with a coating of fireclay mortar mix sufficient to even up the outside. With that done I set about doing the outside arch, which was sized on a larger radius than the inside arch (approx an inch) which would allow room for an oven door to pass through the 'smoke chamber' (The area beneath the outer arch and chimney), and clamp against the inside arch face (critical for sealing oven during baking / long duration cooking). 

This stage happily coincided with Father's Day, and in preparation of the first fire Mrs MikeyC and my brilliant kids kindly gifted me a pizza paddle, oven brush and pizza trays, along with a homemade pizza card. We naturally used the time it took the Archway to set that weekend to take in an episode of a family favourite show - Hey Duggee; "the pizza badge episode" with outdoor oven!

Anyway, back to the Archway...Brickwork archways seem daunting but by getting to this point in the build my masonry skills had got to a level of adequacy. If you are still feeling apprehensive at this point it's worth keeping this in mind particularly after the work you would have done in finishing your oven dome! 

I built the formwork for the dome again from ply/chipboard; using two ply/chipboard arches separated by timber pieces approx 3" wide at the top and bottom of the ply/chipboard forms, and screwed together. The formwork was cut an inch approx shorter than the overall arch size, which allowed me to slot some pieces of loose timber strips below the form so that I could get the formwork arches back out easily after setting. The formwork for the outer arch was used again to form the brick work arch of my oven's log store positioned directly below.

The oven's outer arch was 5no. bricks high with the 5th brick either side cut at an angle to kick off the brick arch. I finished my archway using 2no. separate key stones with a gap/hole inbetween to allow the required smoke opening for the oven's chimney flue. Once formed, I allowed the fire clay mortar(home brew) to set for 5 days (waited until the following weekend) before I removed the formwork.

The Chimney:

I was able to source a salvaged, double lined, metal chimney flue with chimney capping piece at the beginning of my build for free (a great emphasis of the project was to source as many materials either for free or as cheaply as possible!). My arch and chimney would be a combination of brick and steel. I decided to set the cylindrical steel chimney into a plinth/cap of brickwork (see photos). It took me a while to work out how best to join the steel chimney to the brick archway and I sort of made this bit up a little along the way.  I had seen from sources on line that this was a way to go about doing it. Other suggestions where to fabricate further formwork and cast in a cement chimney plinth on top of your archway which the chimney would sit a top (screw fix/bolted through). So far It's worked well - no mortar cracks or brick coming away as yet (heat is intense around this area during cooking -worth noting). The cutting of a semi circular hole into two separate bricks which clamped/formed the hole into which the chimney was set (using fire clay, lime cement  mortar mix) was quite tricky.

Tiling The Plinth And Base:

At about the same time as doing the archway I started to think about what material to tile the base and plinth top with. I'd originally envisaged using salvaged marble or slate, but found both hard to source cheaply. I settled on tiling it with terracotta tiles, which are relatively cheap for the quantities I needed and would sit well against the planned oven finish. They are also easy to cut, and lay. As they are a porous material I needed to coat these with several layers of linseed oil as a sealant. 

[oblertone]

Excellent photo record, thank you for sharing. A removeable flue does make a winter cover more practical.

What's the plan for the dome exterior ?

[MikeyC]

Insulating the Dome:

I firstly wrapped a layer of 25mm ceramic fibre blanket insulation around my oven's dome. I bought 7m's of the stuff, which was enough to cover the entire dome and then double up on top; 50mm thick layer over crown. I bought from Castree Kiln Pottery online. (I used them also to purchase fire clay - quick transaction and delivery within 3 days. Would recommend). I then covered the insulation blanket with a layer of chicken wire which was quite fiddly to work and get an even covering across the dome - the wire I  had bought cheaply had quite large spacings which maybe didn't help? I then aimed to apply at least a further coating of 50mm vermicrete (though this varied upwards to 75mm thick where there was more room; i.e. areas on top of the dome ). I aimed to get as even and as round a dome as I could.

Worth noting that I wore a dust mask during the ceramic fibre wrapping process due to the carcinogenic nature of the product.