42" Pompeii construction in Adelaide

[P3 Stoaker]

G'day All,
Vermiculite all done. Its a fine v-lite and it's coated to be somewhat waterproof, unsure if it made a difference. I worked out I needed about 140 litres I had about 40 already. Sold in 100 L bags I thought to play it safe and get 2 as the place of purchase is an hour away. In the end it probable went on thicker and I was sweating it all day as I thought I'd run out. Made it with about 10 L to spare.
Regards
Greg

[MarkJerling]

That looks very tidy!

[david s]

If you've gone through almost two 100 bags, then you've added around 60 litres of water. Some is used up in the hydration process, but there's still a huge amount of free water left. Allow a couple of weeks drying in the sun and wind (hope your conditions are favourable) before doing any drying fires.

[P3 Stoaker]

G’day all.
Mark, thanks for the positive comments.
David, thanks for the feedback. The oven won’t be fired now for at least 2 months. The main goal at the moment is to get it waterproof as it’s outside, starts raining here in a month or so but I’m completely out of action after two weeks from today.
The ratio I used was 30 litres vermiculite, 3 litres of concrete and I haven’t actually measured the little bucket but I’m guessing about 4.5 litres of water went in that mix. It it a coated vermiculite to somewhat waterproof is so as to reduce the water needed. So for a max of 240 litres of vermiculite I estimate I used 36 litres water.
So for me it’s a question of when can I render ??? I’d appreciate any thoughts/comments on how long I should wait to render. I really want to render 5 days later, and it is quite warm here and dry. What do you think?
I’m not confident I can cover the dome successfully to keep rain off the vermiculite for two months and render later.
regards. Greg.

[P3 Stoaker]

I just measured the jug. It was a little bigger so a total of 48 litres was used. Keen on any thoughts in relation to previous post.
Many thanks.

[david s]

48 litres is still a lot of water. I've not used the silicon coated vermiculite as it's not available to me. If it was I'd try it as it prevents quite a lot of absorption into the grains.I can't find how thick your vermicrete layer is, but from my experience I've found about an inch and a half sufficient. Any thicker and it takes way longer to dry out. Once it's gone white ( around three days of good drying weather) you could probably start some drying fires. I always give it at least a week. A cheap garden moisture meter plunged deep into the vermicrete layer, not at the top because that'll dry first, but about half way down the dome, will indicate when most of the moisture has gone. Alternatively or in addition, you can throw some sheet plastic over the dome during firing to see if it is condensing under the plastic.

If you can't fire it for two months then you'd be better to wrap it in plastic until you can get back to it.

[P3 Stoaker]

G'day David,
Thanks again for the feedback. I aimed for 50mm (2 inch) of v-lite but I suspect it went on a little thicker in places. The whole dome was well and truly white the day after application as its warm and very dry here. I can fire the oven should I need to. The brickwork was completely dry though before insulating and applying the v-lite. I have already run a full set of curing fires up to and including very hot on the 8th or 9th fire. I don't really want to cover the oven and leave it for 2 months unless I really need to as the v-lite is quite fragile and anything rubbing on the surface will cause crumbling.
Do you see a problem rendering after a week or so? I will use a garden moisture meter as suggested. How dry do we need it to be for rendering? It will sit then for around 2 months.
Thanks again
Greg

[david s]

It’s hard to say without looking at your oven and knowing your weather conditions. I do know how hot and dry Adelaide can be. I also know that the appearance of the surface is quite different to what’s deeper in. You can dry it too fast with damaging consequence, but you will never damage it if you go slower than required. If you fired it uninsulated you may have already damaged it. Do the moisture meter thing and if you see visible steam back off, you’re going too hard.

[P3 Stoaker]

Thanks David, I'll get a moisture meter, I had one but ?? I am in a different situation I think in that the brick work is fully dry. I didn't realise about insulating before firing but I'm lucky it survived quite well ( I think) with only only minor cracking as seen in the earlier posts. Once most of the moisture is gone I'll paint with kemcrete and render the next day as the kemcrete is thin and will dry quickly.
I've tested a little kemcrete on the v-lite. Its a milky liquid mixed 1:1 with cement powder and can be painted on to reduce any crumbling when applying the render. Seems to work well and locked that v-lite in tightly.
Thanks again
Greg

[P3 Stoaker]

G'day All,
Back to something a little more familiar today, brickwork. Completed the decorative arch and after considering different methods I ended up using mortar and laying like the rest of the bricks.
Great idea from David S, got a garden moisture meter to check on the vermiculite and after just 3 days there was only the slightest indication of moisture in one probe hole, the other 2 showed no moisture at all. I should note that the dome brickwork was completely cured and dry when the insulation was applied. The dome was completed 2 months ago, I've run a full set of curing fires and we don't know what rain is here.
Anyone have any tips on how to get a nice round shape when applying render on the dome?
Regards
Greg

[MarkJerling]

That's looking very tidy! I've seen one thread where the posted had made himself a special concave trowel. I just used my hands. (In gloves)

[P3 Stoaker]

G'day All,
Thanks Mark, its coming along. I ended up just using a pointed metal trowel for the fine work and a rectangle plastic trowel to apply the render over the larger areas. First coat was possibly up to half an inch thick and cracked on the surface quite a bit. The next day I did the second and later a final coat. They say 3-5mm which I found a little tricky to ensure, with any thicker likely to crack on the surface so I was keen to keep it thin. I wanted a brushed finish but I struggled with anything other than smooth, so in the end that's what it was. This morning I finished with just a few very small cracks at the corners near the entry dome which I have pasted over.
Photo 1 and 2, first coat render.
remaining photo's, final coat.
I'll be out of action shortly for a few months due to work. When I return a few cuts will complete the entry brickwork and I'll install some doors. For now I'm just happy to have the oven waterproof. As I've mentioned earlier, if I had my time again I'd put a roof over it which would be a lot easier than trying to waterproof the whole oven.
I'll remain on line whilst out of action so if my one build's experience can be of assistance please post away.
Regards
Greg

[MarkJerling]

I think you can be very proud Greg; That looks very nicely done! Mine has a bit of a rustic sponge plaster look. I'm quite keen to give it another coat with a colour impregnated waterproof plaster, now that it's had time to settle in. I've only had minor cracking around the flue area so I may look at some mastic sealant for that joint.

[Baza]

Greg, looks amazing! Well done - you've persevered and have, like many of us, learned LOADS!!
Thank you for posting your pics and your journey for the rest of us to learn from!

I'm interested in your vent. I'm reading threads from a number of years ago that didn't use them - now it is recommended we all have one??
I don't really get it.
relieving pressure from what? The entrance isn't enough? - The thought of drilling through the dome to put a big hole in it is not sitting well.
How, exactly, did you do that?

Great finish mate!
Barry

[GreenViews]

Greg, I just popped back into the forum after being away for months. Your oven looks Great!