Weighing up raised earth foundation + earthen floor against decking for a yurt we hope to be living in.
The raised earth foundations I'm considering will benefit from being insulated, having thermal mass and will certainly last longer. May prove to be more expensive initially - there'll be landscaping and excavating needing done.
Excavate area, build a dry stone retaining wall:
Lay fabric membrane, fill up to ground level with foam glass:
Lay membrane, pack in earthen floor using earth from excavation. I'm thinking of screening the earth and stabilizing with lime ala Tataki floors.
View from below:
The only similar foundation I could find:
Any thoughts or ideas welcomed! Can this be pulled off? Will a dry stone retaining wall suffice? Have no experience in the matters of Yurt living or foundation building.
Level the area, lay perimeter of foam glass filled sacks:
Pack the inside with more foam glass:
Stake in some ply formwork:
Install some kind of lime-stabilized/soilcrete/rammed earth floor:
This way the yurt cover will drape over the raised earthen floor.
Earth can be bermed up against the side of the exposed poly sacks to protect them from the elements.
I have to determine what kind of earthen floor will be best to use - given that I'm unsure of the soil type on site and the climate is predominantly damp - we'd be able to stick a tarp over it but that's about it.
Had a reply from Mike Wye, natural builder and foam glass supplier in the UK - here are his thoughts:
Foamed glass would be an ideal insulating base - 100% recycled waste glass, low capillary, great insulation etc etc. I can see that you might need some lateral restraint to keep the foamed glass in place whilst compacting. For load bearing its usually 30% compaction but unlikley to need that in the case of a yurt where there aren't loadbearing walls. Perimeter dry stone walls would be quite time consuming and need a lot of stone but would finish off the yurt aesthetically
Making use of materials on site is good, it depends on your soil characteristics as to how effective lime will be as a binder. Ideally the floro would be based on the sub-soil. Some of the pictures on your link look like there's more lime and aggregate than earth in the earthen floor. In the UK ash was often added to the floor mix both as a cheap bulking agent and as a pozzolan - a material that reacts with lime to create water setting chemicals that harden the floor mix.
I'm never convinced about the boiled/double boiled linseed oil approach as
a. you need vast quantities of linseed oil to seal a porous earth floor
b. you can have an allergic reaction to the amount of oil vapourising into the room
c. these coatings take a long time to harden and dry.
A traditional UK finish was to have a more lime rich surface coat and trowel a source of the protein albumin into the surface. This was often egg white or blood, but there are many everday sources of albumin. Olive soap is another source thats readily available, its often called Marseilles soap.
The action of troweling in a material containing albumin produces a smoother, harder-wearing surface which is water repellant.
...and my reply:
The yurt living hinges on us getting a croft outside of Tighnabruaich in Argyll, Scotland. We've sent off an application and are waiting to hear back...
Glad to hear you're with me on the foam glass, makes a lot of sense. Regarding the lateral restraint, I'm now thinking of sticking the stakes in the ground before the foam glass sacks. This should give them some support - will have to make sure there's plenty.
I will get in touch with the folk on site and see what they can tell me about the sub soil, else I'll do some digging and take samples next time I'm up. Good to know about the ash - I'd seen the word pozzolan being banded about a few places...
Very interesting to hear your thoughts on the linseed oil and the alternative protein albumins. I remember seeing Kevin McCloud playing about with blood on an earthen floor. Always a good idea to christen a place with an animal sacrifice!