Newbie with questions!

[timc]

Hi!

I've been reading a whole lot of posts on here and you guys seem to know what you're talking about, so figured it was time for me to join!

I'm based in Plymouth and have a fairly small space at the end of our recently competed decking in which I'd love to build a wfo.

My basic plan is to build a simple barrel oven using firebrick arches and insulate using 50mm ceramic blanket.

Ideally, it'd look something like this... m.wood-oven-warehouse.co.uk/albums/album_image/7958114/7611397.htm

However with the limited space I've got, I'll have very little room for the external "cladding" - not enough for bricks unless I cut them in half lengthways to make them half width or use slips - which would require a frame underneath I guess...

My main question is: how hot does the external side of the insulation get?

Could I build a wooden frame around the oven with just the 50mm blanket? Or am I kidding myself here and should look at rendering over the blanket instead? - and maybe put a wooden frame over this for rain protection?

Looking forward to getting started!

[downunderdave]

Dec 2, 2016 7:35:46 GMT timc said:

Hi!

I've been reading a whole lot of posts on here and you guys seem to know what you're talking about, so figured it was time for me to join!

I'm based in Plymouth and have a fairly small space at the end of our recently competed decking in which I'd love to build a wfo.

My basic plan is to build a simple barrel oven using firebrick arches and insulate using 50mm ceramic blanket.

Ideally, it'd look something like this... m.wood-oven-warehouse.co.uk/albums/album_image/7958114/7611397.htm

However with the limited space I've got, I'll have very little room for the external "cladding" - not enough for bricks unless I cut them in half lengthways to make them half width or use slips - which would require a frame underneath I guess...

My main question is: how hot does the external side of the insulation get?

Could I build a wooden frame around the oven with just the 50mm blanket? Or am I kidding myself here and should look at rendering over the blanket instead? - and maybe put a wooden frame over this for rain protection?

Looking forward to getting started!

I guess you have a good reason for wanting to build a barrel oven, They are a better configuration for baking lots of bread, but if your primary reason is that you think it will be easier to build than a dome, then forget that. Because the oven is continually expanding and contracting then the dome is a far superior structure because it is self supporting. A barrel oven requires buttressing and bracing to support it and this requires extra suitable design and construction which ends up being more complex and time consuming than building a dome. If you intend on building a small oven then it will require thinner walls than a brick oven will give you, otherwise it will take ages to heat the oven because the chamber is small relative to the wall thickness. If you split the bricks to make the walls thinner then there is insufficient bond between the bricks for a strong enough structure to stand the test of time. A cast structure is a better solution for a small oven and most have walls around 2" thick. 
To answer your questions

1. The temperature of the external side depends on how much insulation you have, but for most ovens you can place your hand on any part of the exterior and it is little more than comfortably warm. If it's hot it means the insulation is wet and not working properly (this happens from time to time after torrential downpours and the insulation gets wet).

2. Lightweight steel studs are better for this application or you can render over the blanket, most builders cover the blanket with a layer of 10:1 vermicrete which increases the insulation, evens out the lumps and bumps of the blanket and provides a firmer substrate to render on to.
A roof over the whole thing is an even better solution, but is more time/money consuming.