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Post by cannyfradock on Jan 12, 2016 19:10:41 GMT
Bento
I'm not sure if I can help with your latest question....but I'll try. I always build my internal arch in "half" fire-bricks. I always use "clay" bricks for the external arch. For the best entrance arch, I use a brick and a half entrance arch. This gives you a better....or easier way of creating a 5" hole for your vent. I have tried using fire rope and on other builds slivers of thermolite block between internal fire-brick arch and external clay brick arch. Both work, but unless you are in a commercial situation......is this really necessary? In a domestic wood-fired oven, a little lime in the jointing compound will transfer the heat back into the dome......that's just my opinion.
All the best with your build.
Terry
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bento
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Post by bento on Jan 26, 2016 20:19:59 GMT
Thanks Chas, downunderdave and cannyfradock (although downunderdave, I think your last post was meant for a different thread!) Have been ill for a while so have not progressed as much as I would have like but managed to finish another course over the weekend. Just thinking about how to top it off. Bottom of hole is around 6" across, top of the hole around 9". Haven't decided if I will do 4 curved quarters, or one long brick with two slim pieces top and bottom. Found a guy on ebay selling some 2 1/2" firebricks (mine are 3"). Picked 20 up at the weekend (maybe overkill), but means I can keep a few 3" bricks back in case I ever need to repair the floor, and use the 2 1/2" bricks with the 3" bricks to complete the entrance arch and flue. Still umming and ahhing over what to do with the gap. It has just occured to me today, that had I continued as planned I would have laid my landing walls direct on to the hearth, and maybe tied them into the dome to prevent the arch/dome joint from cracking. This in turn would have provided a route for the heat from the dome walls to escape down through the hearth - am I overthinking this, or would this have been a possibility? I was also planning on giving the whole dome a coat of mortar (down to the hearth), before insulating. Again, effectively tieing the dome into the hearth, bypassing the calsil board with the mortar coat - or would this small surface area being in contact with the slab be minimal - picture below? Would a lot more heat be lost if the landing walls were also mounted direct on the hearth with no insulation below and/or without creating a heat break?
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Post by cobblerdave on Jan 27, 2016 2:20:17 GMT
G'day For your insulation to be effective it needs to encapsulate the oven. Taking the render layer to the hearth will seperate the dome insulation from the hearth insulation. Even that small amount of cement will allow the heat to escape. Regards dave
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bento
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Post by bento on Jan 27, 2016 18:14:30 GMT
G'day For your insulation to be effective it needs to encapsulate the oven. Taking the render layer to the hearth will seperate the dome insulation from the hearth insulation. Even that small amount of cement will allow the heat to escape. Regards dave Thanks cobblerdave. If I decided against a heat break between the dome arch and the landing, how hot would the very exposed firebrick at the front become? I'm thinking about if I did a gabled roof finish, the stud work would be in very close contact with the edges of the front arch.
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Post by cobblerdave on Jan 27, 2016 20:47:21 GMT
G'day If it were a commercial oven a heat breaks important. A domestic oven well not critical. You'll find the radiant heat from the fire will pre heat the entrance from the inside just in the normal operation of the oven. It doesn't act like a heat sink for this reason. The outer surface doesn't seem to get hot from my experience. Regards dave
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bento
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Post by bento on Jan 28, 2016 10:06:33 GMT
G'day If it were a commercial oven a heat breaks important. A domestic oven well not critical. You'll find the radiant heat from the fire will pre heat the entrance from the inside just in the normal operation of the oven. It doesn't act like a heat sink for this reason. The outer surface doesn't seem to get hot from my experience. Regards dave Ok, thanks. Because my landing does not have a break, I would be adding breaks on all walls, and arch to create a sufficient one. So maybe I'll just consider and expansion gap at the arch and not worry about the landing.
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Post by bento on Jan 28, 2016 16:56:14 GMT
Plugging the dome. Am in a bit of a quandary! The hole at the top of my dome is exactly 6" across. This means it is too big for a final brick keystone, but too small for another course. As in the picture below, can I plug it using 4 x bricks, or do I need to cut out the centre of each of the bricks to allow a final keystone down the middle. I'm thinking I can use four bricks, but obviously need to make it a very tight fit, and not sure how straightforward this is going to be. Can I do it this way or is it advisable to have a single brick keystone to finish? Thanks, as always!
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Post by downunderdave on Jan 29, 2016 0:37:24 GMT
Plugging the dome. Am in a bit of a quandary! The hole at the top of my dome is exactly 6" across. This means it is too big for a final brick keystone, but too small for another course. As in the picture below, can I plug it using 4 x bricks, or do I need to cut out the centre of each of the bricks to allow a final keystone down the middle. I'm thinking I can use four bricks, but obviously need to make it a very tight fit, and not sure how straightforward this is going to be. Can I do it this way or is it advisable to have a single brick keystone to finish? Thanks, as always! If your bricks are the standard size, I'd be shaping two to fill the space. Any excess space on the outer side of the dome can be filled with mortar. Some builds fill that top bit completely with castable refractory.
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Post by downunderdave on Jan 29, 2016 6:35:39 GMT
I was also planning on giving the whole dome a coat of mortar (down to the hearth), before insulating. Again, effectively tieing the dome into the hearth, bypassing the calsil board with the mortar coat - or would this small surface area being in contact with the slab be minimal - picture below? You could add some perlite or vermiculite to the mortar that covers that calsil board below the base of the dome. I'd be using 5:1 perlite: cement if it were mine. Then use you home-brew mortar for the rest. Allow a week (and hope it doesn't rain) for the whole thing to dry before insulating over it. It is much better to dry it out at this stage as much as possible rather than doing it after the whole thing is finished.
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Post by chas on Jan 29, 2016 11:38:29 GMT
As above really - and only added to give additional reassurance... a) the hole at the top of the dome only needs plugging, not 'keystones' in the conventional sense, ie it would happily exist forever as a hole without the dome collapsing. So, just fill it to keep the heat in. Any number of brick wedges will do. b) all insulation is good, but complete insulation difficult. That said, why compromise anything by putting a coat of mortar over before the insulating layer goes on? Keep the dome drying out under some sort of cover for as long as you can bear, then insulate, then render would be my suggestion.
Chas
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Post by bento on Jan 30, 2016 20:47:44 GMT
Thanks downunderdave and Chas! Re-measured the hole and it was 5 1/2", so that 1/2" was just enough to give me enough of a taper to use two 3" bricks with the 4 1/2" length matching the rest of the dome. Packed the gap with my usual mix with a little extra lime and a scoop of brick dust (scooped up from by brick saw). Didn't get quite as accurate a fit as I had intended, but as every angle cut has been by eye, can't complain too much! Looking forward to cracking on with the landing, entry arch and chimney. Will use thermalite slips to insulate the landing and arch from the hearth. As I am now building my arch, where do you get the flue anchor plate, and other flu parts?
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Post by bento on Feb 27, 2016 19:58:48 GMT
Hi, Trying to get some cementing in and fitting around the cold weather, last weekend I started the arch. Calculated it where temps were getting down to about three degrees for the next couple of days, but the third and fourth day after cementing hit freezing. Some of the joints initially look like they expanded/flaked a bit, but then brushing the flaking off it looks "OK'ish" again, just not very smooth (below). First two pictures are what it looked like in the morning, second two pics after I have brushed off the flaking. There is also a very very fine line were the cement isn't fully meeting on one brick (below), but it feels solid to a light tap, and I have filled in the corner behind which has set fine. Not overly concerned about the weight on this brick as the rest of the arch is cut and it will fit very tightly, also not sure of it just the edge which isn't meeting, or if it goes further back. It's very fine (maybe 1/4mm), but it is there. After some advice if anyone thinks this will all be fine or if any of it needs re-cementing? Thanks!
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Post by cobblerdave on Feb 27, 2016 20:53:07 GMT
Gday Temps are so low that that the Portland cement takes forever to cure. Not a problem I have here. Id redo it and tarp it with a 100 watt outdoor light in there to raise and maintain the temps over freezing so it will cure. Regards dave
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bento
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Post by bento on Mar 6, 2016 0:02:50 GMT
thanks cobblerdave, large fills appear solid, but will redo the arch cementing.
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Post by bento on Mar 6, 2016 0:06:03 GMT
On a different note, been looking at some of the finishes on the Forno Bravo forum. There are several builds which have finished the blockwork up with natural stone, can anyone advise if this is likely to be individual pieces of stone, or cladding/slips?
I will probably enclose my done when complete, and would like the entire oven finished in natural stone, just not sure I have the skills to lay, or the money to purchase, that much stone, but would happily finish in slips if it was feasible.
Thoughts?
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