Another WFO in the UK - 42" Pompeii

[brad mole]

I ordered my chimney anchor plate but it didnt turn up in time for the weekend so i just cut the bricks from the spec sheet so i hope it fits ok, I then started the chimney vent transition which took some figuring, and i still havent got it fully figured out, im just taking it one course at a time and hoping it all works out

[UtahBeehiver]

Nice work, just like the dome work.

[cbailey]

Excellent masonry skills! You and I are at the same point in our builds. I ground the bricks for the chimney mounting plate this evening.

[brad mole]

Thanks guys!

cbailey yours is looking fantastic! lovely and neat too!

Been cracking on with the rest of the entry and vent transiton. I also removed the arch former and ground out the mortar joins so i can re mortar them as they were pretty messy where i couldnt get due to the arch former. My anchor plate turned up too and it fits the opening i cut earlier

[brad mole]

Started thinking about my decorative brick chimney layout too, and cut the next layer of the vent transition jigsaw. I have been trying to notch out the end bricks so they hook around the arch supporting everything as much as possible

[brad mole]

Top course of firebricks set too, im so glad im at this stage now! Looking pretty neat inside where it matters, outside not so much but structurally im hoping its ok. tested the anchor plate in place and it fits nicely.

You can see my 10mm heat rope gap here too

[brad mole]

More pics, fitted the heat rope and high temperature silicone and some pictures of the oven as it stands.


Just wondering if anyone can advise me fr my next steps, im hoping to be able to use the oven mid June, now as i understand i want to leave my vermicrete layer around 1 month to dry out? giving me roughly 2 weeks to get to vermicrete finished. I plan on having 100mm insulation blanket then 100mm vermicrete but im worried that wont dry in 1 month and that i wont have time to get it finished, so i was thinking can i just apply the vermicret in a thinner layer, maybe 50mm thick rough then allow to dry, use the oven, then at a later date add the other 50mm of vermicrete, or will it not bond to itself once completely dried out? I was thinking of scoring it to allow the next layer to hold better?

[david s]

The application of any insulation layers is subject to the law of diminishing returns, so 100 mm of blanket IMO is somewhat of a waste, adding additional cost for little benefit. 2 or 3 should be plenty. Also there’s not a lot of merit in having lots of insulation over the top if you have not done the same under the floor. Likewise, are you also planning on a door with 200 mm insulation? The vermicrete over the blanket does 3 things, firstly provides additional insulation and secondly to restore the form of the hemisphere covering lumps and bumps of the blanket layers. And lastly provides a firm substrate to render the outer shell against. 100 mm thick will take forever to dry. I find a layer of around 35 mm 10:1 vermicrete dries daily well in a couple of weeks good drying weather. If I’m doing a thicker layer I usually do 35 mm followed by a week of drying then another over that.

[brad mole]

The application of any insulation layers is subject to the law of diminishing returns, so 100 mm of blanket IMO is somewhat of a waste, adding additional cost for little benefit. 2 or 3 should be plenty. Also there’s not a lot of merit in having lots of insulation over the top if you have not done the same under the floor. Likewise, are you also planning on a door with 200 mm insulation? The vermicrete over the blanket does 3 things, firstly provides additional insulation and secondly to restore the form of the hemisphere covering lumps and bumps of the blanket layers. And lastly provides a firm substrate to render the outer shell against. 100 mm thick will take forever to dry. I find a layer of around 35 mm 10:1 vermicrete dries daily well in a couple of weeks good drying weather. If I’m doing a thicker layer I usually do 35 mm followed by a week of drying then another over that.

Thanks for the info David!

I have already bought the materials to apply 100mm of ceramic fibre blanket and 100mm of vermicrete so i dont mind doing it if it will make small improvements as its all paid for now, my main concerns were can i apply one layer at a time and do it in two thicknesses a few months apart which by the sound of it i can do if thats what you have done in some cases? did you have to scratch the surface on the first coat so that the second coat bonds well?

Also i do plan on having an insulated door, maybe 150-200mm deep if possible and i have 100mm of cal sil board under the floor, so minimum of 100mm insulation all around

[david s]

Ok, get yourself a cheap garden moisture meter to test the drying of the vermicrete if doing it in layers and don’t go more than about 35 mm for each layer or it will take way longer to dry.

[brad mole]

I made the final arch former for the decorative brick arch at the front of the landing, i also raised up the 'gazebo' so i had room to work on the insulation, put another layer of foil around the calsil just for a bit of protection (not that its going to do anything really) and got the blanket on too. I was hoping for 4 layers of 25mm but i started to run low on my third layer so i just stopped there, 75mm has got to be good enough? I then tied it down with wire and fixed the chicken wire on by snipping and tying with more wire. Bit of a pain to work with but managed in the end

[brad mole]

So i also received my 900mm 8" Selkirk twinwall chimney! I started on the vermicrete too, i read a lot about people using it and being worried it wasnt going to be strong at all and not very easy to apply as it is very dry, i can see what everyone means now, first layer has gone OK but i think next layers will be a pain as i wont be able to use the formers that i have for the first layer, its going to be a bit of a freestyle. How long should i leave it before i remove the former? and how long before i can apply the next layer?

[UtahBeehiver]

I made a home made curve trowel to help place and shape the vcrete, roughly the height of each layer.

[brad mole]

Thanks Russell, i knocked up something similar to shape the rest of the dome, it worked really well actually and i found this part pretty easy, although its not perfectly neat i dont mind as i know im going to add another layer in future when this layer dries out properly. I started the decorative brickwork too

[brad mole]

First layer of vermicrete complete, bottom part already looking a little dry which is good. I also i cut my last set of arch bricks, for the decorative entrance arch. I also laser engraved 2019 into the keystone, i was going to put my name but kept it simple instead