How to Build Open Fireplaces

Updated February 21, 2017

Open fireplaces are simple to build both indoors and out. Earth-based fireplaces are common in Europe and work best in smaller homes. Heat efficiency is greater when using earth as a sculpting base for your fireplace because thick earth holds heat, radiating it out into the home gradually over time. For an open fireplace, using earth as the base for this art piece can enhance the look of any home, while adding more energy efficiency than an ordinary, masonry based fireplace.

Plan your open fireplace so the earth or stone and clay-formed chimney goes outside through the roof. The strongest chimney is made round and goes straight up. Load two buckets of clay-heavy dirt onto your tarp. Dance on this pile to your favourite music, stomping, twisting and squishing the mud mix while slowly adding straw and water. Pull the corners together regularly into the middle while continuing the stomping and twisting with your feet to mix. Keep going until it feels and looks like bread dough.

Move the dough-like mass of earth/clay onto the pre-made rock, tile or firebrick base and shape the clay into a fireplace box. Some prefer to stack or mortar fire bricks or stones into back and/or side walls. Load the damp earth between them while firmly pressing them into each other. Keep all visible surfaces clean and clear of mortar. Install or shape any shelves, cooking racks or grills.

Weave copper tubing into this soft earth structure, so the opening ends of the coil are inside the firebox pulling or pushing heat. The copper coil climbs around inside the fire-hearth walls. Open up the stone or firebrick area in front of the fireplace, where the log-grill will be. Designs you follow should showcase the stone and hearth designs in front of your open fire box area in front of where the interior log grill will be.

All hearth and shell walls need to be as thick as possible while maintaining an attractive shape. Use the copper tubing to distribute heat into the earth hearth where you want it to radiate out into the house, or into sculpted benches, bun warmers and other around-the-fireplace shapes. Determine how to size the stovepipe by measuring the front of the stove/fireplace face span. The stove pipe should be 5 to 6 inches smaller than the span across the front of the fireplace opening. Refer to a building guide book for best results.

Send the rounded, coiled, smoothly-shaped chimney you created using the earth/clay adobe mix up and out of the upper back of the fire box. Install the damper where it best serves draft control for the size of your box. Seal any area around the chimney with wet clay, coating or sealing it later with oil melted with wax. Use melted wax to seal other potential cracks. Put a stovepipe metal cap on the top after embedding the mesh screen into the earth over the topmost hole.


Any local hardware store has a £3 bag of white gypsum plaster. This is usually enough to coat the inside earth walls of a whole house. European design adobe fire hearths are appropriate for smaller homes. Locate your fireplace in a central area on a firebrick, tile or stone base. It will radiate the most heat into the biggest areas of your home from here. Clay/earth mixes can also be used with stone as mortar with small amendments to the mix.


If your clay/cob isn't sticking or holding enough, add more clay. If it is drying too much and is too full of cracks, add more sand and plaster. Prepare for several days of mixing and shaping adobe for your fire box, stove and chimney. Practice coiling clay for the fireplace chimney with your earth-clay ahead of time to become familiar with the process.

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About the Author

Johanna Parry Cougar began writing for local newspapers in 1975. She became a columnist, poet, grant writer and nonprofit director. She is published in newspapers and bioregional journals such as "Access" and "Raising Power." She holds certifications in art from the Art Institute of Seattle, and has taught sustainability, earth sculpting and green home construction in five nations.