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Post by russell on Apr 20, 2015 21:01:57 GMT
After much poring over this WFO forum we have made a start. We have begged stolen or borrowed all our materials as we are on a tight budget, and have been quite successful The plinth is done, breeze blocks with reinforced concrete lintels across to support big 130mm thick blocks. The piers will be rendered in due course .  On top of the blocks we will lay 25mm ceramic fibreboard and on top of that storage heater bricks laid straight on the board.. Because of the difficulty of cutting the storage heater bricks we will trim them roughly to size along with the board and build the dome on top of them, The hearth surround will be bulit up with concrete and laid with 6 inch terra cotta tiles. The dome will be old clay brick using fireclay sand lime and cement mortar, we have some tapered firebrick for the internal arch. Question; The concrete lintels are level, but knowing my bricklaying skills when the breeze blocks are put on top using mortar I will have one hell of a job maintaining that level, which is critical as the fibreboard will go straight on top. So do you think they could be laid dry, as the concrete slab on top for the tiles should hold them in place, along with the render on the outside?  Is it OK to lay the storage heater brick for the hearth straight on to the fibreboard (they are recessed slightly on the underside) or should they be laid on sand? Any thoughts would be appreciated. |
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Post by oblertone on Apr 20, 2015 23:18:06 GMT
I laid heater blocks direct onto vermiculite board without any sand or other filler; works a treat !
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Post by russell on Apr 29, 2015 11:34:04 GMT
Good progress made last week. Base and dome completed. Time for a break before phase 2
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Post by russell on Apr 29, 2015 11:49:54 GMT
     Not the prettiest of domes but I have faith. It's 32" internal diameter for info The plan is to build the outer hearth, landing and flue, then to cover in ceramic blanket and chicken wire Do you NEED to stick the blanket? I feels as thouggh it will be easy to form around the dome and then hold in place with chicken wire. There are no plans to use the vermiculite porridge, just to render over the wire direct. Is the render just sand and cement mortar? 5 to 1? Do you add anything? What thickness should it be and do you layer it on in stages or all in one go? Will it be waterproof or do you need to seal it with something? Anyone used mortar colourant? So many questions , sorry. Any thoughts would be appreciated |
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Post by highlandladdi on Apr 29, 2015 18:41:41 GMT
Looks good!
No need to stick the blanket. If you use the ceramic stuff it sticks to everything (including itself) very well. I'd Vermicrete over the wire as it's cheap and works, it also stops the heat from getting through to the render.
I used a render mix 4:1 with additive, then painted the dome with masonry paint. Easier that messing about with pigments. I'll post a photo so you can see what 'Cornish Cream' looks like! Comes in about 1,000,000 colours so you'll be ok!
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Post by oblertone on Apr 30, 2015 7:54:30 GMT
I did as you suggest and just rendered over the chicken wire holding the blanket; however I did 'cure' the dome and used it extensively before I put on the blanket layer, no point in trapping the moisture.
My main reason for not using a vermicrete layer was lack of space and while my oven works as well as I need it to it could probably have benefited from more insulation.
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Post by russell on Apr 30, 2015 11:38:36 GMT
I'm lacking in space too Oblertone, and it is primarily a pizza oven. The plan is to cure the dome before rendering; How thick did you make your render?
Are we talking about a waterproofing additive highlandladdi or just a plastciser? As there will be no rigid vermicrete layer to render on to i reckon a 25mm layer of render would be thick enough?
Thanks for your help
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Post by cobblerdave on Apr 30, 2015 12:25:08 GMT
G'day
You can render over the ceramic blanket it fairly stiff enough and 50 mm of blanket is more than enough insulation. I found working with pearlite cement was awfull stuff and used a layer of rockwool and rendered To a layer of chicken wire.
I've since used pearlite cement and it's still the Devils Porrage but it's stll useable
By the way 4 ins of pearlite cement is equal in insulation value to 2 inches of ceramic blanket or sheet.
Regards dave
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Post by oblertone on Apr 30, 2015 14:35:12 GMT
I suppose my render layer was 1-2cm over a 25mm layer of ceramic fibre blanket; my 'render' was actually waterproof tile adhesive as I then tiled over the render layer. External temp gets to about 40c which I think is acceptable given the limitations of my build.  |
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Post by highlandladdi on Apr 30, 2015 18:17:45 GMT
It was Cementone Integral Waterproofer, and a very good job it did too. Lots of other brands out there, and I'm sure they all do petty much the same thing!
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Post by chas on May 1, 2015 7:05:08 GMT
I'm lacking in space too Oblertone, and it is primarily a pizza oven. The plan is to cure the dome before rendering; How thick did you make your render? Are we talking about a waterproofing additive highlandladdi or just a plastciser? As there will be no rigid vermicrete layer to render on to i reckon a 25mm layer of render would be thick enough? Thanks for your help If it's purely cosmetic, ie unless you want to add mass, then K-Rend base coat + a top coat is very easy to apply and it's self-coloured, needs no other finishing. Chas |
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