ovens and earth bag construction

[Annie]

Re: ovens and earth bag construction

Good to know! We only need to extend the space in front of the oven enough to suport the oven landing...... 6 to 8 more inches! I will check over at the habitat for humanity store for some old counter top or?.

[SpringJim]

Re: ovens and earth bag construction

The perlite insulation mixtures are generally not a structural layer and we try to minimize the amount of portland in the mix. It can be soft like styrofoam....strong enough (non compressible) to hold up your oven if it's on a solid base, but not a material used by itself for strength.

How big a piece do you need? Can you find a waste piece of countertop or a large sink cutout to do the job?

[Annie]

Re: ovens and earth bag construction

How structurally sound is the pearlite /cement mixture?

We have decided to make an overhang in front of the oven earth bag base. We thought of using cement board to overhang an additional 6-8 inches, making a bender board form on that, then pouring the 4” pearlite /cement mixture slab, reinforced with rebar on to that. Will it support someone using it to pull themselves up? Could I stand (135 lbs) on it to prune the wisteria?

[Frances]

Re: ovens and earth bag construction

Wow, I'd love to try that, it looks fantastic!


But... I need a bigger garden!!

[Annie]

Re: ovens and earth bag construction

The soil needs to be a mix of clay and sand. They have all kinds of different formulas for that work. We have mostly clay soil here so we could just use what came out of the trench plus a little more we dug up down the hill. The sand came from our dry creek bed, we have about an acre of that! Our formula was 20% clay soil and 80% sand + water. The first coat of plaster was also just clay and sand with some straw added. I have heard of people using what ever type of soil they have for the bags. It is considered a "sustainable" building method, as little to no wood is used and the only cement is in the foundation. (It takes more energy and money to make cement than it is worth) My next project will be a wine cellar. All underground and round like a kiva, using the soil we dig up, what ever type that may be (probably clay). It never ends!

[sarah h]

Re: ovens and earth bag construction

Wow, that's going to be one awesome space - I'm looking forward to watching your progress! Do you need a special type of soil to use those bags or will any soil do?

[Annie]

Re: ovens and earth bag construction

I have been fondly called Dirt Bag Annie, and yes the bags are awesome building material. The mixture inside dries and becomes a 12”W by 5”H by 14”L solid brick. Feed sacks make even bigger, better, thicker walls…..Cheep too, in this case the soil, sand and water came from the site so I only bought the bags at 25 cents a piece. (and of course a minimal amount of other building material.) After constuction the bags are covered with in this case adobe plaster and the a few coats of lime plaster to keep them from breaking down over time.... unprotected 10years, protected.. who knows, the missions are built with adobe.
The oven base is back filled with “farm debris” (Terry is standing on some in the pic, he isn’t really that tall) and will be topped with a slab, then insulation.
Even by reducing the back width of the oven dome brick I may still have to extend the slab out in front about 6 inches. We will give it the same curve as the base. That will hopefully blend in with all the curves around it.
The whole project is a giant canvas, constantly providing me with new areas to be creative in and on.
Thanks for all the ideas and feedback!

[asudavew]

Re: ovens and earth bag construction

This gives new meaning to the term "dirt bag".

RT

Haha Now that's funny!

[RTflorida]

Re: ovens and earth bag construction

I LIKE IT!!!

This gives new meaning to the term "dirt bag".

RT

[asudavew]

Re: ovens and earth bag construction

I know little to nothing about adobe.
So I am curious.. Can the adobe filled bags hold the weight of an oven.
I would be afraid they would get wet and shift or settle... or shrink.. or something.

Just wondering.

I agree with BaconGrease.
It is going to be a beautiful place to hide from the world!

Dave

[BaconGrease]

Re: ovens and earth bag construction

wow that is going to be one sweet sitting/standing/cooking/eating area.

[Annie]

Re: ovens and earth bag construction

Awesome!
So ....I reduce the size of the brick at the back for a couple of courses, then add 2 inches of blanket and fill in any additional space between the wall and the oven with vermiculite. Sounds good!

Now by using an extra inch of the blanket all around, that reduces the vermiculte by 2 inches... correct? 1 inch blanket = 2 vermiculite?

Someone say pictures? Be advised.... this project is my baby!

[SpringJim]

Re: ovens and earth bag construction

I also think that reducing the wall thickness in the back will work fine, particularly if you fill the space with board or insulating perlcrete. If that back area is solid, (between the adobe and the oven) it will help to also support the dome in that area and insulate where you need it.

The thin FB board would be best but you can suppliment with the perlite mixture.

Pictures might help!

[Frances]

Re: ovens and earth bag construction

This is just a thought, but maybe you could also reduce the length of the entry archway and curve the chimney back a bit after the vent - that could give you more room on front of the oven, too.


As for the landing in front of the oven... if you build the oven so it looks as if its coming out of the wall (which sounds like a cool idea btw) I would imagine that it would look good if you had a free standing shelf poking out from the wall just underneath the oven door. It doesn't have to be out of cement, could be marble, granite, slate - or whatever goes best with the adobe surroundings.

[dmun]

Re: ovens and earth bag construction

You could reduce the thickness of the back wall of the dome by half without sacrificing anything structural: there are only a few bricks that you would have to cut, and they would be on the lower rings, that heat up last. My whole dome is only 2 1/4 inches thick and it works fine, although I now think a thicker dome is more structurally sound. With two inches of insulating blanket between the thin back wall and the rear wall you should be fine.

Any drawback? When you are throwing logs in your oven with wild abandon, remember you're aiming at the thinnest part of the oven.

Sorry if I misunderstood your question originally.