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Rammed Earth Walls
We had originally thought to use rammed earth blocks for the walls but concerns about their timely supply convinced us to think again.
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We liked the earth but our earth building experience with the pump house (it was poured earth) convinced us that choice was not appealing.
Acquiring the forms and moving 80-some tonnes of earth, at times lifting some of it 3 metres in the air were both discouraging factors.
Getting Ready
We subcontracted locals John Oliver and Gabor Farkas, then owner-operators of Rammed Earth Constructions to build the walls who not only had all the gear, they had expertise as well.
The formwork is arriving and being piled up around the site. |
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| Work starts on the first section of the first wall |
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Moving up
With a team of 5, enthusiastically aided by Norman and I, the walls took a total of 13 days to complete.
We started at the northern corner and zigzagged our way around the walls - always working as far away from a freshly-done section as we could.
Some days we would finish 3 wall sections, other days fewer - it all depended on how much earth could we mix, move, form-up and ram before sundown.
The weather was very hot and dry so the walls started out drying rapidly and we had to keep gently spraying them to give the cement in them a chance to start forming crystals. |
Layer by layer
Because the earth is rammed together it is only possible to do a layer at a time, even so you can see layers where the bottom is not as compressed as the top.
The earth is all shoveled in by hand to get an even distribution and a depth amenable to ramming solid.
A compressor-driven pogo-stick rammer is worked around the bottom of the space formed by the steel shutters compressing the contained earth.
the shutters are held together by bolts and 300mm spacers make them keep their proper distance apart. |
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The first section stands
The walls had been heightened to 3 metres because the shutters were 600mm high and it just didn't make sense to try and finish a wall half way up a shutter if we wanted anything resembling a flat top to the wall.
By the time the top of the wall was being rammed we were 3 metres up in the air. |
Shoveling the earth into the forms became an adventure something akin to high-wire work in a circus.
Happily workplace health and safety did not ever choose to inspect us but scenarios like this were obviously begging to be improved.
A significant improvement
A pair of brickies trestles were summoned and a platform perched atop with a large shallow tray which served as an admirable raised reservoir for the earth.
This removed some of the adventure but speeded progress dramatically. |
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| starting the form work for another section |
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The cycle goes on
Each wall section started with getting the end shutters and corner forms in place and absolutely vertical.
These are made entirely from steel and were about as heavy as one person could lift - there was not much chance of fine-tuning the positioning alone.
Some sections would need 5 of these juggernauts precisely positioned before we could add the formwork to them. |
The large mixer
The mixture used was a combination of 3 different earths, 5% cement and 10% moisture content.
Each load was about 6 bobcat buckets of earth, 3 bags of cement add water to moisten, mix well with bobcat.
The earth was on the dry side and the weather was very hot and dry so we were very grateful for the unlimited supply of springwater delivered at high pressure right on site. |
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a load is mixed by the bobcat |
| The bobcat delivering |
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And so it went
While the walls were being built Norman and I had our hands full preparing and locating the forms for the alcoves and electrical conduits.
These had to be rammed into the walls at the correct location and there was no going back if we missed getting a single one ready and into place before the earth had been rammed past that location.
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and went
The RAC crew usually finished by 3pm but Norman and I would often be still at it after 9 at night - wire brushing the wall surfaces to eradicate the unsightly dents and lines left by the edges of the formwork.
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a distant view
of a work in progress |
The alcoves debate
I was keen to add some character to the walls as we built them and had decided on alcoves - it seemed a good idea, make up some wooden shapes, put them in the formwork, ram the earth around them, remove them and, hopefully, a space would be left.
John and Gabor were skeptical and insisted it was infeasible, wouldn't work and was not to be considered by any sane builder. |
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The first set of alcoves out the forms |
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The alcoves are sane
However, being the man with the money persuaded them to “at least have a go”.
Time and engineering facilities were limited so we used more of the 12" X 2" oregon and a 45° circular saw to cut pieces which, joined together - would create 100mm deep forms with angled edges for easy removal. |
Room for improvement
And this was the result - a set of alcoves in the first wall section.
This certainly looked good to me and a very welcome counterpoint to the bland featurelessness of some rammed earth walls.
The bottoms of the alcoves were quite uneven (from the ramming) and difficult to see what we could do about it other than pour cement in or lay a tile to fit.
We had, at the time, a heap of granite and sandstone pieces we had “rescued” from a landfill and thought they could be rammed in with the earth and form a nice flat bottom for the alcoves.
And so another task was added - cutting the bottoms of the alcoves with a grinder. |
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| The alcoves mk II - with granite shelving |
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And the result
A set of alcoves with granite bottoms.
By this stage I had discovered that a semi-circular router bit made a lovely channel in the oregon formwork and........
it seemed obvious to me to use the faces of the formwork to make more “decorations” and so the alcoves mk II came into being - to add symbols to the surfaces.
Once again I was regaled with professional advice that it was infeasible, wouldn't work and was not to be considered by any sane builder.
Once again the financial argument won out and these were the result - I did treat the relief work to lashings of bondcrete as soon as I could get at them.
After 11 years they are showing no signs of deterioration. |
Smothering the dust forever
The final step in completing the walls is a coat of earth-bonding emulsion which soaks into the surface down to about 3mm.
As its name suggests this glues the surface of the wall together and prevent it from forming dust.
It is a PVA compound - heavily diluted with water for spraying and simply sprayed on with a pump. |
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the coat of earth bonding emulsion |
| rain water covers the kitchen floor |
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The wet arrives
The first storm of summer arrived and brought heavy rain - presaging a wet summer, little did we realize how wet.
This was the first rain since we had finished the dwarf walls and we soon discovered that we had made no allowance for drainage in the rooms with no plumbing.
and most of the main room |
Visual termite barrier
We had spent a lot of time chasing non-toxic termite solutions and eventually decided on a stainless steel mesh to lay on top of the dwarf walls (beneath the earth).
While talking with the lass at termimesh about what widths to order etc I described the application to her and she said that we wouldn't need it because the 75mm exposed concrete would constitute a "visual termite barrier".
The theory being if the concrete is properly compacted, the termites won't be able to burrow through it and will have to build a track across the surface which can be seen and destroyed. |
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the visual termite barrier - simple, toxin-free, elegant and effective
apparently unknown to building inspectors |
Come the final inspection the inspector wanted termite treatment certificates A and B. We had none and he said he'd let us get away with just the "B" certificate (I think the A one deals with pre-construction spraying which was clearly impossible at that stage). My explanation of the nature and function of the visual termite barrier seemed to mean nothing to him.
Fortunately Trijntje had been doing massages in one of the rooms and her massage table was still in there. When the inspector saw it he exclaimed with delight that his girlfriend did sports massage too and he instantly decided to mark us down as "termite treatment not applicable".
Strange but true and a classic demonstration of the fickle nature of building inspections.
Best advice I received re inspections is to book it for Friday afternoon when the inspector won't want to waste any time finishing the inspection and getting off to the pub.
| Gabor grinding a housing for a lintel beam |
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The lintel beams
Each of the openings needed a header or lintel beam made from stable, strong material.
We had acquired some seasoned hardwood timbers which we felt would look in keeping with the massive thick earthen walls.
These had to be set into the corners of the walls and over the cyclone rods either side of each opening.
First the housings had to be ground and chiseled out of the walls. |
Another “good” idea
It seemed sub optimal to let the lintel beam slop around in the housings so I had the bright idea of filling the housings with sand after the beam was in place.
A good seal could be made be rolling up some malthoid (the bituminised felt) and squeezing it into the gaps on either side.
No - seriously it was a good stable solution for about 5 years. |
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View from above ~ It seemed a good idea at the time |
And then we noticed small piles of sand on some window sills - the seal had stopped working 100% - possibly with the help of some rats, but we have had to revisit these “seals”.
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The finished picture
One by one we went around the building measuring and gingerly inserting the lintel beams.
The earth walls - for all their solidity, were quite fragile enough to crack if we were to try to force a beam into the space against the wall's will.
Eventually all the beams were in place.
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| Another look at the finished product |
And now, a word or two about those pillars
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