New build in Nottingham

[simonh]

So the pics above show how the build for the bbq bit ended but I am a little ashamed to say I still haven’t built the grills and so have never actually used it! I am now all recovered from my chemo (that took 3 times as long as the actual chemo) so all the things I have on the backlog are now starting to get done, such as the chimney.

[simonh]

Well all the vermiculite insulation is pretty wet, the oven itself was sodden inside so the leaks were worse than I thought. I’ve ordered more vermiculite and I am going to mix it with some cement and make a solid mix that will help stop the water ingress. New chimney is working well though

[downunderdave]

Apr 22, 2019 21:00:30 GMT simonh said:

Well all the vermiculite insulation is pretty wet, the oven itself was sodden inside so the leaks were worse than I thought. I’ve ordered more vermiculite and I am going to mix it with some cement and make a solid mix that will help stop the water ingress. New chimney is working well though

Do’t render over wet vermiculite, it will just extend the length of time to dry it out. Gentle prolonged fires until you’ve driven out the moisture, then render over it. I’ve just completed some water absorbency and drying tests on a number of insulating materials. A 10:1 vermicrete doubles it’s dry mass in a 5 sec immersion while a 5:1 vermicrete only about 25%. But surprisingly a total 24 hr immersion has both taking up around the same amount of water and both samples took the same time to dry completely. Some sheet plastic thrown over the oven during the drying fires will indicate via condensation how dry your oven is.

[simonh]

Last night I pulled all (well as much as practically possible) of the vermiculite out of the cavity. I'll have a couple of fires to dry out what is left and then I'll refill with vermicrete this weekend.

[oblertone]

I've contemplated building my next oven with a dry vermiculite fill over a bare dome as I'm well aware of the insulating properties of vermiculite, however I now fully appreciate the need to prevent water ingress. Have you considered a pent roof to shed water rather than a flat surface ?

[simonh]

The longer term plan is to put a roof over the whole oven and BBQ, that is on next years list of garden to-do's

Simon

[downunderdave]

Apr 24, 2019 8:14:09 GMT simonh said:

Last night I pulled all (well as much as practically possible) of the vermiculite out of the cavity. I'll have a couple of fires to dry out what is left and then I'll refill with vermicrete this weekend.

So are you planning on replacing wet loose vermiculite with wet vermicrete? Doesn’t gain you much. Long prolonged fires will eventually dry it out.
Dry vermiculite should weigh around 70 g/litre, 10:1 vermicrete 360g and 5:1 540g. You can approx double the mass if the vermicrete is saturated, or around half its volume of water. Saturated vermiculite will hold around 2/3 of its volume of water.

[simonh]

so my problem is water getting in under the flat roof, I was hoping with a 5:1 vermicrete mix would provide more water ingress resistance than the plain vermiculite has done.

[simonh]

Well I’ve gone with a 7:1 mix and back filled most of the cavity today, even with an extra 100l of vermiculite I still didn’t have enough to fill the cavity.

[downunderdave]

So now you’re back to square one. 100 litres of vermiculite requires around 30 litres of water to make vermicrete. Approx. half of that is taken up chemically in the hydration process leaving you still with a lot of water to eliminate. As it is only exposed at the top, the weather won’t assist you much in its drying.

[simonh]

Yes but once it is dried and sealed I think it will be much more water resistant than the loose vermiculite. Only time will tell...

[simonh]

Another 100l of vermiculite arrived today so I managed to get the cavity fill and all of the oven covered. There is still some space that could be filled but I haven’t yet decided if I am going to do that. Either way I will leave it a few days and then get some drying fires on the go.

[simonh]

Had a good sustained 6 hour fire in the oven yesterday, and still plenty of heat in the floor today. Going to do a fire every other day for a few days to drive the moisture out before I put a roof back on.

[simonh]

How time flies! Not sure where all my pictures have gone, the are all still in the same location on my hosting provider and if I copy and paste a link into a new window they are visible?

Anyway the oven barely got used last year with the weather being so crappy, but because I hadn't finished the roof it sat under a tarp for most of the summer and all through the winter. The good thing about that is that when I can to fire it up the other week it was lovely and dry and required no drying out fires at all - which I was super pleased about.

I ended up with a semi dome of vermicrete and a significantly bigger chimney (which works wonderfully!), there is a cement render over most of the vermicrete and I have some rend-x to apply as a waterproofing finish next time we get some decent weather.

However having cooked pizza the last two weekends I think I have a problem with my internal dome height, the bottom of my pizza is cooking much faster than the top, the height at the apex of my dome is 530mm, my arch is 300mm high by 450mm wide. the floor size is 0.635m2 (or 115cm deep by 57cm wide) does anyone have any thoughts on that?

[simonh]

and I've been using it to do a bit of cold smoking