First earth oven build

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I've been doing a lot of reading, watching, calculating, etc., and am about ready to start my first earth oven build. Of course, each time I learn something new I also think of a new question. Here are some of my current ones, hoping someone might be able to answer:

1. I've seen where people are putting a final coat/seal on their ovens, but I thought I read that it needs to be breathable, and figured a sealant would stop that. Am I missing something?

2. Trying to figure out the best way to construct the mouth. I think I may go with a simple brick structure, but can decide between an arch and a square one using one of the metal right angle things. I saw in one place that a person's arch had begun to sink; is this common? Would using mortar for this step prevent this (I think cob is more common between the bricks)? If using a square design and bracket, do people cover the metal bracket? I figure they must, or else it would look pretty bad, but couldn't find a good image/description of how.

3. Happened to see a youtube video in which the oven was built on top of a stout wooden square frame/table. Is this really possible? I figure that you could make a good 6" or more base for insulation, and leave some extra room around the edges so the wood didn't heat up too much. I know part of the beauty of these is the stone base, but really, if this were on locking casters, I could get it out of the weather without having to build a roof (which the wife doesn't want, and I admit it would break up the patio a bit).

Well, that got a bit long, but I'm trying to think of everything before I'm actually knee deep in mud.
Thanks for the help and all the inspiration around here!
Brian

[cobblerdave]

Re: First earth oven build

Gudday
Firstly I'd better tell you I have a WFO built of forno plans but like you I did a lot of reading before that.
Waterproof a clay dome.... Yes it is possible. the main problem is that the cement render will crack with the expandtion of the dome. a way around this is to use ceramic blanket and render over the top. the blanket will be a cushion.
a cheaper option ( yes I have seen this used on a brick oven) Is to firstly cover with an insulating layer of clay and chopped straw then use domestic insulation then chicken wire and render.....be warned only use the "rockwool" after a fireproof insulation layer it will melt as its to hot against the dome.
Building an arch... My first attempt was a failure but I finally finished my oven with a simple arch in front. I used payers cause there only 50mm (2in) thick and allows smaller mortar joints. Build yourself a guide using two bit of Ply or chipboard the shape of the inside of you arch. Screw a couple battons of wood to the first then screw the secound on that. Using a saw set to the thickness of the material cut both in half. Now you have the battens hold the form together and it a simple matter of unscrewing the form apart to make it easy to remove from your completed arch. To make you arch strong you dont need any mortar on the inside edge of the pavers only the outside thicker part of the joint in this way each of the individual payers is resting on the next not on the soft mortar.
Makeing it movable.. well of course its possible whatever you build is quite a lot of mass not easy to move even on a flat surface. this link might help
http://www.fornobravo.com/forum/f43/...els-16229.html
Finally a good read would be Allan Watts book "build your own wood fired oven" It has no plans as such but explains how to build a cob, a cast and a brick oven. Rosenberg Publishing

Regards Dave