Troglodium             Living underground

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Cordwood / Stackwall

          Basically it consist in bedding  desired length logs in 2 stripes of masonry cement, leaving the center empty  to avoid thermal bridges . You stack-up this way for about 60cm to a meter high per day, depending on your cement  consistency. Stacking up too high at a time might affect the chemical bond that is in process on lower freshly made layer. Cement and concrete don't like to cure fast so some protection is needed against the sun and dry winds. Wetting the cement while curing is recommended. Once it is sufficiently dry, brush out the surplus of cement for a nice finish. Some people will put in insulation in open spaces while going up, a technique which is relevant in above ground situations but not here because we will have a vaporproof barrier on the outside surface of the wall  and we want to avoid a dew-point  formation in the wall.

            All the steps seen on this page were done without any electricity only a chainsaw, a gaz-powered drill and cement mixer, shovel, buckets, wheelbarrow, rubber gloves... basic tools...but if you have electricity; cut your logs with a sliding miter-saw which will give you clean cuts and exact lengths. It can all be done by only one person but a team of three is best; one cement maker, one on log preparation and another as log installer.

           While building up install electrical wires, related boxes....my stair steps are integrated in the wall....wires, plumbing vent, water heater tank, pipes, chimney goes thru the 2 meters wide central pillar.  When you get to the first floor make sure to put under the butt of beams a transversal plank or concrete  to spread  the load on a wider base.  For roof beams I made a small reinforced 'footing' on top of the wall to spread equally the load and added anchors in it to attach the roof with the wall. The roof deck is made of used studs nailed together making a full 6.5 cm ( 2.5 inches) thick, primed and covered afterward with elastomeric membrane to seal it. A below ground grading insulation board will cover and protect it from the 10 cm of sand + at least 30cm of earth rich in organic matter. A double layer of criss-crossed plywood would make a strong roof too, thickness determined by total (actual plus lively or seasonal) load and structural support.

          The same elastomeric membrane is used to seal your wall from the earth humidity and water. More available than ever, it is relatively cheap, easy to install and safe. Having worked with 3 brands I can advise you with Bituthene3000 which is still excellent, Blue Skin WP200 is very good with a neat peel-out plastic strip which protects from sand, dirt and insects for the postponed or unfinished job. Resisto (residential line product) seems to have a problem of adherence on the overlapping part, resistance to the traction forces between stripes might suffer a lot.

            Basic mortar recipe is in volume; 1 part Portland cement, 1 part lime, 3 parts of granular sand (the more varied in size  the better, don't use sand that is homogenously too fine or with any organic matter) and water which will vary depending on the humidity already contained in your sand... If you go with pre-mixed mortar (more expensive and less trouble) make sure you will be able to get the same brand for the whole project because the greyness may vary from one another.

           Don't seal your roof apertures (chimney, vents...) until the expected earth load on your roof had time to settle the building, at least overnight.

            Depending on your extracted earth, chances are that you might need to get some gravel near the outside wall to drain the water as fast as possible. In my case the extracted earth was too clayish and many truck loads of adequate aggregate were needed. While burying the operator will put the gravel near the wall and use the excavated earth as filler, make sure to add first some earth on the top to compress the vertical wall.

           The Canadian Mortgage and Housing Corporation recognise the cordwood/stackwall as an efficient wall system, see their section 7 .

           Now get the rake out. Help nature by sowing or let it go wild like I did and manually extract the undesirable or overwhelming plants in the following 2-3 springs, then once every 2-3-4 years depending on your climate. Indigenous plants are highly resistant and maintenance free.

           All in all it is lot of work, yes, but not as hard as it might seem and even kids could help. Dried logs are very light, two buckets of cement is ok and remember that big arms & pick-ups are just for the show !  You certainly can do it too.

After all this work it is time to hook up the hamac and....................................

..............................................................................................enjoy.

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.............................................Dig it ?

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End of march 1983,  ready



Second floor



Load spreader



Months later



Simple curved wall



Ready for membrane




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