Glory Be

Earth Sheltered, Green Roofed, Cordwood Root Cellar

On this page, find out:

• all about the planning and design of the earth sheltered root cellar.

• the excavation of the site

• how to build the root cellar roof

• details for how to build the cordwood walls and the green roof.

Glory Be, the root cellar was conceived because I wanted a place to put homegrown organic vegetables for winter storage.

The most intensive and frustrating part of the project was finding information and specifications for root cellar construction.

The criteria are simple; dry, or at least not really damp, and above freezing in the winter (preferably without the use of electricity) and maintaining a fairly low summer temperature.

Using these few rules, I resorted to the 'seat of the pants' method of design for Glory Be.

I was also very interested to try out two alternative building methods; cordwood construction, and a green roof.

Luckily, there is more information out there on these techniques.

The Excavation of the Root Cellar Site

I determined that the ideal place to build a root cellar was right into the hillside, using the mass of the earth to shelter it and keep it at a relatively stable temperature.

A neighbor with an excavator was enlisted to dig out a hole.

After much deliberation, losing a track on the hoe and almost falling into it, a hole was dug.

Most of the soil was sandy, with a few large rocks at the bottom, so drainage isn't a problem here.

The hole was around 3 meters deep (10 feet), and 3 across to make a finished root cellar of around 2.4m square (8 feet)

The actual usable size was a little smaller, due to the way it was constructed, with the metal on the outside and the frame on the inside of the root cellar.

A small footing was built with concrete, and a frame of 2x4" lumber was constructed.

On the outside of this frame was screwed metal roofing which was carefully back-filled with the soil.

The floor is just earth, with a layer of gravel over top.

This ensures the higher humidity for vegetables such as carrots that keep longer when kept moist.

Building the Root Cellar Roof

A roof of two layers of oriented strand board topped with rigid blue foam insulation, and then a large piece of rubber roofing above that was constructed.

The epdm rubber roofing was purchased from a pond supply company. It comes in two widths so I adjusted the measurements of the root cellar to accommodate the narrower size of 16' - 5 meters approximately.

This allows for an overhang down the sides to prevent excess moisture from getting to the foundation and increasing the humidity inside.

Once the rubber was in place, a layer of old hay was put over the insulation of blue board Styrofoam.

(It was discovered later that the ants love to burrow in the blue board, and sprinkle it in little piles on the floor - in hindsight, it would be better to actually pour a thin layer of concrete, then put the insulation above that, then the rubber, then the backfilled soil.)

The roof was back-filled with between eight and ten inches of soil, and eventually planted with many different Sedum; I especially recommend these green roof Sedum.

For a different system of building your green roof, see how I built a modular green roof for a quick and economical option.

The front walls were built out of one foot (30cm) long larch cordwood, which was mortared with a mix of Portland cement, damp sawdust, lime and sand.

This was mixed in small batches in a wheelbarrow, as each layer of cordwood has to set up before building the next.

The book by Rob Roy Cordwood Building, The State of the Art, was an invaluable resource while building the root cellar.

This book contains the recipe used for the mortar, and was extremely useful for the many hints and tips it contains, too.

The middle of the wall was insulated with dry woodchips mixed with lime to prevent insect infestation.

So far, four years or so later, there appears to be no major cracking of the mortar, which was a concern.

I stacked the cordwood in place to dry before mortaring them together.

Building the homemade rustic painted door was fun; it’s made of two layers of plywood over a frame of two inch thick lumber filled with rigid blue insulation.

I painted the outside to look like old wood, and surprisingly, after four years of full sun, winter cold and lots of abuse, it’s still looking as though I only just painted it.

The paints were acrylic craft paint, coated with two layers of spray on urethane.

The Sedum Roof

Planting the Sedum roof was done over a couple of years, depending on if I had spare Sedum plugs or plants available. There are many kinds of Stonecrop that have been trialed for use on green roofs in Europe to choose from.

The soil is about two inches (5 cm) of Sunshine mix over top of the several inches (15 cm) of native soil, and then the planted plugs are mulched with lava rock.

Once the plants get big enough to run into each other and fill in, it’s going to look great and in full bloom it will be spectacular.

There are many other green roof plants that will thrive in these challenging conditions including Andropogon gerardii, the big bluestem, and Ratabida pinnata, the Mexican hat which reseeds itself every year.

Other xeric plants are suitable too; look for those that have a fine netting of roots rather than a tap root, as there isn't enough depth in the soil for tap rooted plants.

The temperature inside the earth sheltered root cellar on the hottest days of summer will get up to 17-20 degrees Celsius, and in the winter when outside temperatures can reach -25 degrees Celsius it’s kept about 4 degrees inside by the help of a 60 watt bulb.

As it turns out, it maintains the ideal temperature for keeping my worm farm for vermicomposting.

All things considered, Glory Be is a hit on all fronts. Visitors are fascinated by its hobbit house appearance.

I also get frogs and crickets and the occasional alligator lizard living in the cool damp inside, so I have to watch I don't crush them by accident.

The one in the picture has lived above the door for two years, and very casually moves a bit when I carefully open the door, and then settles down again in the same spot - he's not giving up the best seat in the house!

I'm very satisfied with the way Glory Be turned out, and I highly recommend it as a fun project to build in any xeric garden.

Green Roofs

Blue Fox Farm

My Sedum and Succulent Nursery

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