We generally associate the termite with trouble. Termites can be destructive little things, but they are also a great source of very useful building materials for us.
Termite mound clay is a terrific ingredient that can be used in cob oven construction. This post details the specifics for you.
Why cob ovens use clay.
Clay is one of several ingredients used in a typical cob blend and is the primary material that seals and binds the whole mixture together.
Termite nest clay has properties allowing the cob mix to be shaped and formed into the oven chamber and once dried, the oven is quite capable of standing up to years of use. Pure clay is rarely used because it is seldom found.
The average clay used in cob oven construction is a mix of clay, sands, gravels, and soil.
Put aside the different kinds of clay used in cob ovens just for a second; the primary defining factor in the cob oven design is the thickness of the clay cob walls. We detail why it matters in an article titled “How thick does a cob oven wall need to be?“.
Is termite mound the same as clay?
A termite mound is formed from tiny granules of clay by the termites as they mine and tunnel out their nests. It The nest material is a form of clay.
Because of the termite’s behavior with clay use, any time a cob mixture uses termite mound as the primary clay source, it is possible that the cob mix will be as strong if not stronger than a hand-dug clay mixture.
As well as the clay particles, there is a lot of fine sand in the termite nest blend as you will see in a image further down the page.
A few hours’ drive from where we live here in the wet tropics of far north Queensland, Australia, there are large termite mounds that have weathered some of the harshest conditions you can imagine.
These mounds are subjected to torrential rain for several months of the year and then baked in the hot sun for the rest of the year. These mounds are famously known as magnetic termite mounds.
The grasslands where many of these mounds are found are burnt off every few years as well. They are tough and prove that using termite nest is perfectly suited for cob oven use.
Disclaimer. We didn’t use the clay from these wonders, but far smaller old abandoned mounds.
Will termite mound cob wash away in rainy weather?
Termite mound clay is very weather resistant but not entirely weatherproof. The cob oven should be covered if possible and sealed with linseed oil and clay render at a minimum if left exposed to the elements.
The back face of our cob oven gets a fair bit of weather on it, and it is standing up ok after seven years. It will need a touch-up soon, but it’s mainly cosmetic.
Some defects have presented themselves over time, and these are related to air pockets in the cob as it was smeared over bricks we made from termite mound clay and scoria.
For information on using scoria in cob, we have an article titled “can scoria be use in a cob mix?” and it explains if, how, and why.
Will termite cob burn from the fire in a cob oven?
Termite mound clay is very fireproof. In fact, it can be fired into a form of terra cotta.
The mounds in the Australian bush have a very rough time of it all year, every year. Bushfires often burn around the termite mounds and don’t seem to damage the clay at all. The fires appear to harden the clay.
The fires may even help season the external face and make it more weather resistant.
How long will a cob oven last with termite mound in it?
When a cob oven is made with termite nest material and if the oven is undercover, it should last decades.
The actual lifespan of a cob oven built with this material is unknown, but our data suggests that it should last a very long time with good maintenance.
If the cob oven is treated with a render made from crushing termite nests into fine dust and mixing this with linseed oil, it will become quite weather resistant.
Is clay better than termite mound in cob?
Clay and termite mound are equal because the termite nests are made with fine clay particles.
One could argue that the termite mound clay might even be superior to local clay sources dug up for mud oven construction.
The attributes we all look for in clay used in cob recipes are present in termite mound clays. The great thing about the termite clay is the little insects have done all the hard work for us and filtered all the larger stones and pebbles from the soil.
Is termite mound easy to work with?
Yes, it is very easy to work with.
The nest is broken up with hammers or similar and eventually broken down into fine particles that can then be mixed with water, some sand, and the straw stalks you selected.
The cob mix behaves the same as any other good clay-based cob blend. It can be smoothed as a render without difficulty and will hold a shape if the moisture level is correct.
It will not slump if stacked like the fire pit in our rocket stove cob oven. That fire pit was shaped in one stage without any issues at all.
The termite mound clay can also be mixed to form bricks. We formed long cob bricks using the termite mound and scoria as we noted above and then used a similar mix with less scoria as the final 2-inch coat over the entire oven.
Would we recommend using clay from termite nests?
Absolutely yes, we strongly recommend using this material when you can.
The nests or mounds we used had been abandoned by the critters, so no harm was done in their collection. The day trip to get them was enjoyable.
The nests break apart easily with a bit of effort, and the cob mix works wonderfully, both while you build the oven, but also as a functioning cooking item. We do rate the material very high.
If you are looking at building a cob oven of any sort, we recommend starting with an article titled “How do you design a cob oven?“. We also have another article on the different types of ovens titled “Cob oven or rocket stove oven, what best suits you?“
If you are after more, then we suggest you go to the top of the page and click the search icon and enter “cob oven”. It will get all the articles we have all in one place for you. There are many separate posts on oven design, construction, and use here on site.
Article by Tim Blanch for TheTropicalHomestead.com. He is a qualified Permaculture designer.