Building a round timber framed structure, approx 3m x 3m into a steep slope using Earthbags

Hi,

I've been doing some Earthbag retaining...

It's a very steep slope, made of a mixture of silty / clay / organic matter and 75% granite rocks in the hills of the Welsh border lands. My first retaining wall is around 1m high, this is 3m wide and is where my floor begins, I have built it one layer underground with a 200mm deep drainage coarse of rocks underneath. From here I want it to go back into the hill by 3m, this will require an earthbag retaining wall of 1.5m high. What should I be thinking about, its 75% rocks of varying sizes, so do i need a layer rocks behind it? i guess i should run a drainage pipe underneath the wall, maybe one half way up?

Love to hear from you,

Many Thanks
Erol

Hey Erol,

Can you share some pictures to help visualize? My main concern would be getting the earth bags covered in some sort of plaster, because they will degrade in the sun.

Nathanael Szobody wrote:Hey Erol,

Can you share some pictures to help visualize? My main concern would be getting the earth bags covered in some sort of plaster, because they will degrade in the sun.

Yeah, i'll cover that front sun facing part with rocks and lime etc. and the back wall will be rendered in lime by the time im done.
/
My main concern is this 1.5m high wall and what i should do since i'd like the space to stay as dry as possible, would a plastic sheet help i wonder?

My first choice for that site would be a pole house.
With large poles set into the ground, then timber beams and floor joists to create the flat floor.
It would not be suitable for a soil building with the pole designs.
Some questions;
- IF the 1.5M wall you mention going to be at back, up the slope, the downhill wall will need to be about 2.5M high? is that correct?
- Have you thought of building a stone wall?

I'm planning a somewhat similar earth sheltered structure here. I'm hoping that a rubble/gravel filled trench behind my wall will be enough to keep it dry. But my structure will be stone, so a bit of damp won't cause too much trouble. Have you looked a paul's wofati concept? The idea there is for the roof/walls to always go downwards so that the water pressure never builds up. He also lives in a somewhat dry cold climate, unlike Wales (or Skye)

wofati concept from'build a better world book'

more information about wofati here

I may even turn my building around to open up behind it on the uphill side, although my thoughts are that driving rain is just as likely to casue damp issues as soil moisture wicking.

I've built a lot of structures on my steep property, and I won't build any structure unless it is on a flat, level surface, then build up from that so that all of the stresses are equal on all sides, and so the structure won't start leaning downhill.  Gravity is not your friend.

There needs to be almost overkill in the foundation, including a very deep concrete retaining wall down into the soil at depths of 3 feet/1 meter to 4 feet/1.3 meterrs on all sides of a steep slope with rebar extending upwards that the bags are on.

Be aware of all the forces on a structure:  wind, soil density, rodents digging under it, erosion, and roof drainage around the foundation, tree root intrusion, the weight of the building.  Over the years, even a few years, all of these things will come into play.   You'll end up struggling to keep something like that in its original condition if even one of the above things starts to change or is effected by heavy storms or earth movement.   Just like any retaining wall, it needs to be leaning back into the hillside.  Check out retaining wall construction on YouTube.

You might want to look into a mini earthship that uses tires for a back wall, then you could use earth bags and a wood frame along the front.  Or check out a mini hobbit-type house.   There is one guy who did a hobbit house where the back wall is backed into the hillside, and he dug out an extra deep excavation behind the back wall, filled it with concrete that was attached to the back wall as an anchor of his hobbit house because of the weight of the soil pressing against it.

That will tell you how serious it is to build on a slope, even if it's on flat ground.

Check out YouTube for either of the above.

You won't want to have this structure on the list for needing to be fixed in the future.  You'll have plenty of other things to do.

:-)

I put another message here, but I don't know where it went.  That picture of the house with the rounded roof is a hobbit house, but it's on flat ground.  There is a hillside behind it.   Be careful not to destablize the hillside and what's above it if you decide to dig it out.   Retaining walls need to lean back into the hillside, not be straight up and down.  All drainage should take water away from the foundation, including downspout water.

Christo, do you have links to the Videos you speak of.
Also, retaining walls need to have a heal and toe, if made of concrete so that the soil assists in keeping it stable and harder to "roll" over.

The front wall will mainly be window frames, the 1.5m back wall is from how much earth needs to be retained in order to go that far back and achieve a flat floor to the front. The earthbags are for the primary reason of getting rid of the dug out soil. Its a long way up this hill from the road with poor access and carrying materials up there is an exhaustive process, which makes concrete or any such thing not ideal. This is why I thought retain those walls using earth bags and any excess soil can be used to build up the walls, then timber frame the rest, as i do have a fair bit of timber laying around.

So, as far as dealing with the gravity of a 1.5m wall perhaps i should start it a little further forward to allow it to properly lean into the hill behind, Perhaps I could run a perforated plastic pipe along the edge of each coarse of earth bag for drainage? I cant really bring a load of concrete up here... but on the plus side the soil is predominantly granite rocks as the geography here is upon an ancient granite outcrop.

Hi !

One practical option would be to slope the roof clearly to one side, or even better, make it shed water forward in a controlled way, so it ends up away from the back wall. Then you could guide that runoff with a shallow stone-lined drain or rock-filled swale in front, so water does not linger around the structure. On this kind of site, keeping water moving is half the battle. Earthbags can be a good idea, but I would be careful about assuming all bags will age well. Some do not handle UV exposure or long-term weathering very well, so if any part will see sunlight for a while, I would protect it as soon as possible. In a project like this, drainage and durability matter more than optimism, gravity always works.