Arrifana Pines Cob Oven

25 Aug

Arrifana pines 20/8/2016

Cob oven building workshop.

I was invited to Algarve to help building a cob oven. My friend Paddy finally found his place in Europe after traveling along the Atlantic coast in his camper van. I am happy that his dream final came true and he is a proud owner of a beautiful house near some famous surfing spots in Algarve.

Before arrival we were consulting location of the oven and I gave a shopping list to Paddy. There was an existing BBQ shelter already and the logical position was to include the oven into the structure.

Ahead of our visit I was forwarding loads of different designs which I have found, so the final design can be finished once we arrive.

building with cob

Building with Cob book is a must have for any cob building project

Intention was to have the platform for the oven ready for the workshop.

Paddy wanted to have a wood storage beneath the oven. Initially we wanted to make a cordwood wall to support the oven but as the oven building workshop day quickly approaching we ended up in local builder store and went for the easy way with concrete blocks.

masters builders

Masters builders gettin the platform up

Cordwood wall would be ideal as there islots of timber from the land available. Another reason why we build with blocks was insufficient time for the cordwood and clay wall to dry out.

not so much natural building

not so much natural building or finding shortcuts

The oven has some serious weight especially with the wet sand used to shape the dome

after building the walls we used pine logs to create the platform.

pine logs base

pine logs base and layer of cob

We placed the logs on the blocks and used pieces of marble to level the tops. The gaps were then filled with cob mix and leveled.


monster from the logs (we hope thet it’s friend wont eat the base…)

We found some interesting creatures living under the bark of the logs. The logs were quite fresh so we didn’t remove the bark and hoping that the fire from the oven will eventually drive them off.

upcycling bottles

upcycling bottles for the insulating layer

The air trapped in the glass will insulate the fire bricks layer and aids to faster heating up of the bricks. it also protects the logs from the heat. We used bigger and smaller bottles to create a flat surface as the logs were not the same size.

insulating layer leveled

insulating layer finished and leveled with dry sieved soil mix

After leveling the bottles we used the dry soil to fill the gaps between the bottles.

laying fire bricks

looking for ideal layout for the fire bricks

Fine silica sand is used to create a bed for our fire bricks, which have to be level so the melted cheese doesn’t escape from the pizza.

laying fire bricks

laying fire bricks on the fine silica sand.

Couple of firebricks harvested from old storage heater were used to provide space for continuous fire for those big pizza parties planned in Arrifana Pines. We used pieces of marble to separate the part for the continuous fire and area for cooking..

Once we were happy with all the fire bricks being in place we started to build the sand form to support the fire clay dome.

sand form building

sand form being shaped while fire cob mix is getting mixed

The wall need to start at right angle from the bricks to leave space inside the dome for a bread to rise. keep the sand moist so it is holding its shape.

sand form

sand form being shaped into perfection

We shaped the dome and the door entrance. The door needs to be approx 63% of height of the dome to have a good burn of the fire.

chimney up

chimney up and insulating cob layer following

For our cob oven project we included a chimney as well as there is plan to include a cob bench and a roof eventually. the chimney is not necessary but if you build a roof you don’t want to have smoke inside  the shelter. position the chimney just where the top of the door joins the chimney.

While the final shape of the dome  was being sculpted we started to mix the fire clay mix.

clay samples

clay samples shower ideal clay content for building

Test of the local soil shoved roughly 70% of sand and 25% of clay which is the perfect mix for this. You don’t want your mix too wet so it doesn’t slide off. The the fire clay mix creates inside of the oven and needs to be 5 to 8 cm thick.

sand form

sand form covered with wet newspaper to separate the layers

We started from the bottom laying the desired thickness around our sand form. By adding the mix in layers we were keeping an even thickness of the fire clay mix.

first coat of fire clay

first coat of fire clay coming up

Following a spiral around the sand form we finished the inside layer which will be burned by the fire. While one group was finishing the first layer, others were digging out and sieving some more soil for the insulation cob layer.

perfect soil

perfect soil just behind the wall

Other helpers were jumping and dancing on the tarp to mix the soil water and straw to create this ancient building material.

mixing dance on the cob

mixing dance on the cob is good for you!

We were aiming for 12 to 15 cm layer of cob as the second layer of the oven. As this is an insulation layer we were trying to mix in as much straw as we could into the mix. A good fast method of building this layer is to shape pieces of the cob as bricks and laying them in spiral fashion.
Important thing is to pres your thumb into each few times to make the straw bond with the layer beneath.

Around the chimney we only used the clay mix to avoid burning straw. As the oven will be drying small fires can be used to speed up the process. Crack might appear and will need to be filled with some clay mix

Of course the sand needs to be taken out first. This can be done next day, but it was our last day in Arrifana pines so we were just chilling. Now it is Paddy’s turn to finish the masterpiece…

well deserved dinner

well deserved dinner – Giulia’s famous foccacia and Dublin veggies

Looking forward to taste some sourdough pizza and sourdough bread from the wood fired oven!

traditional way of building - rammed earth ruin algarve

traditional way of building – rammed earth ruin algarve

Martin Obst

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