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Post by Calaf on Feb 6, 2012 16:43:48 GMT
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Post by Calaf on Feb 6, 2012 16:46:12 GMT
A small Barrel Vault Oven designed to fit snugly in a tight space.The oven will serve primarily to cook pizza and occasionaly to bake bread and or grill meat. It will be used about once per week in the Summer months but will also see occasional use through winter. Oven materials will be fresh Firebrick, recycled Ironstone storage radiator bricks, Refractory Clay and insulated with FB Board, FB Blanket and Vermiculite. The oven will be blockwork enclosed with a render coat and painted. The roof will be rendered flat and the front facade constructed with red clay brick. I'm a keen DIYer so my skills are minimal but enthusiasm high. I intend to take it slowly and allow mortar to cure between stages. First firings will be conservative as I don't want to create steam cracks on first use. As I progress I shall tot up the expenses at each stage. All comments are welcome, even critical ones. In fact especialy critical ones as I welcome all input and advice. I'll need it Mark
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Post by Calaf on Feb 6, 2012 16:49:05 GMT
So here is the plot with topsoil removed and my foundation slab poured in. As you can see, the oven's plot is cramped between a fruit cage, small deck, patio and a cherry tree. No poofy smoothing of the slab as I will not be building a woodstore (and I've mislaid me floor trowel somewhere). Now, the dimension of the raft foundation are 150mm thick x 1200mm wide by 1100mm deep. No, that's not a typo. I'll explain what I intend further on. So far the cost is Portland ------- £5 Wickes Ballast --------- £8 Wickes Builders sand -- £0 leftovers Gravel --------- £0 off driveway Total ----------- £13
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Post by Calaf on Feb 6, 2012 16:51:42 GMT
To fit into that space of 1200x1100 I am going to vault out at 35 degrees. Here is the design of the base, with celcon block hearth on top. Three courses of blocks x 4 (so from the front elevation you would see 4 walls edge on) and backfilled with heavy rubble, of which I have a fair bit to dispose of, to add stability. Then a raft of mortar to hold a concrete base of 50mmx1200mmx1800mm. A 40mm lip to the sides to allow for render coat. The front wall will be capped with waterproof tiling board (the stuff you use for showers, made of thin concrete) and rendered. To keep the chimney mass as far back as possible I will use the same board as the back wall of the oven enclosure in place of blocks.
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Post by Calaf on Feb 6, 2012 16:54:21 GMT
I've been working out the size of the oven and how much space it will need on the base. Consequently I find I can reduce the length of the base by 300mm. This has two major advantages: 1- the base need only vault out at 30 degrees and 2- with less overhang I can use 38mm flags instead of 50mm monsters that weigh 70Kg each (I wasn't looking forward to lifting those.) One disadvantage is I will have no space at the front to perch a bottle of wine or glass of ale. Adjusted diagram. Now I need to stop fiddling with plans and get out there with me trowel n mortar.
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Post by Calaf on Feb 6, 2012 20:47:46 GMT
That looks an awesome and original design, not seen a sloping base like that, looks like a good plan to me. Cheers Marcus Hi Marcus Mojitos are one of my favorite cocktails btw. I've calculated the sloping base should be stable. It's 30 degrees giving a 300mm overhang. Any load on the overhang should be transferred down those 4 supporting walls. The rubble and concrete backfill providing stability against the mass of the chimney breast wanting to topple it forward. I'm sure people have looked at it and thought, "It'll never stay up." Vedremo!
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Post by Calaf on Feb 6, 2012 20:49:24 GMT
Fine weather we're having eh? In between bouts of drizzle I've managed to lay a couple of courses. I used some celcon blocks I had left over from another project. They were cut by sawing a few mm into them all the way around with a rusty saw and splitting off with a wide cold chisel. I've put in a damp-proof course to help prevent moisture rising up through the blocks and because they have been out in the weather for 2 years I am using the damp ones at the bottom and the drier ones atop. I'm also putting some empty sand bags at the bottom of each cavity before filling with rubble. It's taking me about 4 hours per course, 1 course per day. Pretty poor work-rate. Terry would probably have all three courses done in under 2 hours. I've no chance of catching up with Rich361 in NZ at this rate. Costs Portland ------- £5 Wickes Builders sand - £6 Wickes DPC ----------- £7 Wickes Blocks -------- £0 leftover Plasticiser ---- £0 leftover Total ---------- £19I think the sand was a bit dodgy as I kept finding the odd gravel chunk in the mortar.
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Post by Calaf on Feb 6, 2012 20:51:11 GMT
I dislike windy weather more than rain, so little progress likely this week. Thinking ahead I've redesigned the arch following a comment from Turkey. Laying the floor bricks flat would improve heat-up (at the expense of thermal mass in the floor) and reduce brick count. This is a 20% reduction in brick count per arch and still providing close to the typical 3'x4' oven size. At 600mm x 920mm the ratio is a nice 1.5ish. Height to width is also circa 1.5 giving a vault apex of 385mm. Using the 63% rule my aperture arch will be around 245mm high and 535mm wide. Plenty of height to slide a chicken brick through but wondering if it's too wide? If thermal mass should be insufficient it will be possible to supplement it with a minor re-build. The addition of quarry tiles to the oven floor, for example.
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Post by Calaf on Feb 6, 2012 20:52:26 GMT
Cazzo! Sideways rain has circumvented my attempts to keep the work dry. But a little sunshine today and I've got the third and final course done, buttered the joints and filled up the centre cavity with rubble ready for a concrete top-up. Instead of filling the side cavities I'll just put in two pillars of old celcon cut-offs. Brutto figlio di mignotta, but it'll be rendered pretty. I've added a corballed support to the centre column to distribute the load of the chimney, where most of the mass will be. (Note how I skilfully use technical terms to make bodging sound professional.)
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Post by Calaf on Feb 6, 2012 21:03:08 GMT
Nice bit of corballing work !!! The usual route is to "timber shutter" .....even with a central supporting wall, the underneath of your slab, then later remove the shuttering through the void created for wood storage. Your design is concrete laid on a full slab.........nothing wrong with that.....as long as you protect the slab from drawing damp out from a full base. I always advise to have an "air flow" below the supporting concrete slab. This I've learned through trial and error. I would suggest 2 things to you....1...make double sure no moisture gets into your solid base and 2....lay a polythene membrane (thicK plastic sheeting) between base and supporting slab. One of the main objectives after the build is keeping moisture from entering dome or cooking hearth. Wood fired ovens of any form will always work, but if you can keep them dry, then fire-up times, heat retention, less wood used etc will all add to a better cooking experience. Terry Thanks for the advice Terry, just what I need. Ventilation: as I've decided not to bother filling the side cavities I left a gap in the blockwork (front wall, just visible in photo). I can drill some holes in the back wall to provide through-ventilation and will make provision for the front fascia. Damp: I put a DPC over the first course and empty plastic sand-bags under the rubble back-fill. If you think this is insufficient I can either -- paint the top of the base with bituminous paint (liquid DPM approach, I have a tin in the shed) or -- use some spare polytunnel sheet I have (just like membrane but transparent). What do you suggest?
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Post by Calaf on Feb 6, 2012 21:08:11 GMT
Calaf I look forward to more photos of this project I'll be posting plenty of Photos, Tom.
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Post by Calaf on Feb 6, 2012 21:10:16 GMT
Every oven project seems to require some shuttering and reinforcement. So here you go. Tastes good, too.
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Post by Calaf on Feb 6, 2012 21:11:55 GMT
Calaf Looking over your earlier posts I now see the dpc on top of the first course. Normally this would be enough, but just in case moisture gets into your support walls it would be a good idea to put another barrier on top of the walls. Bituminous paint is the best option as it will reduce the chance of any "sweating". ....nice picture.. Terry Bitumen paint it is then. Pillars and fill complete. I've rubbed down the mortar with a wire brush and given it two coats of thinned pva in prep for rendering. Now I'll leave it for a few days to, weather permitting, dry out some before laying the base slabs.
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Post by Calaf on Feb 6, 2012 21:13:08 GMT
Looking at the arch design posted above I realize I still don't have it right. Superimposing the entry arch on the vault there is a gap. On other oven designs I notice people have used a step down from the vault to the entry arch of angled bricks. However, I am limited in depth so cannot use that approach. (And I suck at bricklaying.) A quick redesign... I think this gives a better aperture at 18 inches wide and still high enough to slide a terracotta chicken brick through.
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Post by Calaf on Feb 6, 2012 21:14:10 GMT
One last bit of support before the base is topped with pavers. Two 8mm x 40mm steel bars notched into the blockwork.
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