Cobitat-Maui

An attempt to structure my daily log into usable notes.

Prep

Have piles of clay, rocks, sand, gravel, and road base surrounding the site. Hopefully many of these are locally sourced.
Acquire necessary tools and estimated materials.
Have shady/rain-protected spots for storing tools, bales, etc. Tarps tarps tarps.

We'll likely use a rubble trench foundation, which will support the massive weight of the walls and also protect them from water on and under the earth.
Width is determined by the stem wall, about 1"-2" wider than stem wall. E.g. 18"-19" for a 17" wide earth bag.
Depth should traditionally go beneath frost line, but both Conrad and Kyle have stuck to 2' max depth for rubble trenches.
- The logic here is that the water when freezing can expand into gaps of the rubble.
- However, depth might have to go farther to create 2% drainage grade.

Use pick ax and shovel to dig, and hoes to straighten edges and level trench bottom.
Dig a square bottom, not a rounded U shape.
Tape a level to an unwarped 2'x4' to measure slope of the drain
- Remember that bubble touching level line equals 2% grade.
Take the lowest part and extend it away from house, about 10', then "daylight" it.
- IIRC, when ground isn't sloped, instead of daylight you can send it to a bigger digout with drainage gravel - verify this.
Line the trench with a landscape cloth (water permeable but keeps soil out of trench so as not to clog). Leave enough cloth on either side to fold over the trench surface once it is filled in.
Fill in bottom with big rocks (or french drain perforated PVC w/ the landscape cloth around it) to allow large water flow.
Fill in the rest with 3/4" drainage gravel.

You'll need to trench a water inlet under or through the rubble trench.
- This water inlet should be beneath frost depth.

Stem wall goes directly on top of the trench (on top of the folded landscape cloth).
If flat ground, 12" stem wall (~ 3 earth bags high) is sufficient.
When sloped, can compensate for a level floor by making stem wall higher on the lower ground. Conversely, an interior step can create a lower part of the interior floor
For determining when to stop, start at the highest point of the slope, determine the floor level + 6 inches as the top of the stem well, and use a line level to mark this height along the rest of the walls. The rest of the walls should exceed this height.
Build in/outlet pipe(s) into stem wall in strategic locations for waste water, electric, etc. 4" PVC likely convenient for fitting stuff.

Flip bags inside out for softer corners
We filled ours with:
- Roadbase: 3/4 bucket
  - Tip: shovel road base from different areas of the pile to ensure variation
- Sand: 1/2 bucket
- Soil: 1/3 bucket
- Portland Cement: 1.5 - 2L
- Some water to mix
Mix in a wheel barrow with two hoes.
- Clean tools after using cement!
Always "marry" the first two bags of a layer (seam to seam). Subsequent bags can be placed with seam against existing bags.
Tamp the bag down until you hear the WAP (not to be confused with Wet Ass Pussy).
Dimple the seam with a mallet, like legos. Dimple before the cement sets!
Round corners with mallet. This is only relevant for the outer side, and the last layer or so of the inner side (the bottom layers will be filled with gravel on the inside).
If the structure has any square corners, make sure those corners have full size bags for stability (half bags etc. should only go on straight wall sections).
For round buildings, you can shape the bags by tilting more material on one side of the bag, creating a diagonal top.
Can just stick in/out pipes between earth bags.
Keep earthbags plumb as you go up! Plumb every bag before/after tamping and shift it around to make plumb.

If making a threshold for entrance, just have 1-2 layers of earthbags there to start.
Height should be close to finished floor height.
Make a level & plumb plywood form, and use metal landscape stakes with holes for screwing into plywood.
Fill form with rocks, suspended rebar, some hardware cloth kept a few inches away from the form.
Pour cement mix into form.
- Should be made with a similar mix to the earthbags, but add extra cement and 2L lime as well.
- Mash it into crevices with sticks and 2x4s.
- Scree the surface with a 2x4 in arcing and sawing motions.
- Final trowel it to ensure smooth (but don't overwork!)
Hard trowel after it sets to smooth it.
Periodically mist it as it dries to prevent cracking.
After removing form, fill the space between the form and the rest of the stem wall with appropriately sized earth bags.

You can find second hand windows, but make sure they're double pane and that the seal has not broken otherwise they will have condensation issues.
During build, leave windows off to the side away from construction, covered from weather so they don't warp.

To create rough frames, create 2x4 rectangles for the window to sit in, with +1/4" of wiggle room on each side.
- That is, given 47.5" x 71.5" windows, create a 48" x 72" rough frame.
Ensure rectangle by measuring diagonals.
Then brace into shape with 45deg beveled pieces on the interior.
- Or plywood triangles if those are available instead.
Stick nails/screws/2x2 wings into the sides to grab the cob.
- Do not stick nails on the top side, which will not sit in cob.
- Nails in the bottom are optional?

Once the wall has reached the desired height, place the frame on the wall and brace it with e.g. 2x4s connected to the frame and then staked into the ground with landscape/cement stakes.
It's desirable to position the window closer to the outer edge of the wall, but make sure there's at least 2-3 inches of the wall on the outer side of the frame to support the frame.
Continue building wall up around the frames.
- The 2x4 on the interior side should be covered with cob.
- Curve the inside wall towards the frame for a nice light reveal. TODO pic
- The 2x4 on the outer side should not be covered with cob; the window flange will screw into this part.
Leave a 2" gap of cob above the window frame, then install a lintel.
Wait as long as possible to actually install the windows, so they're less likely to break.

Needed above doors, windows, and any niches that are not arch shaped.
Lintel should be $x$ inches in height for $x$ foot span.
Use 2x4 blocking to span lintel across the width of the wall
Optional: use pretty non-dimensional lumber for the exposed interior/exterior pieces of wood.
Use nails etc. on the lintel sides to grab the cob (I think?).
After placing lintel, use hardware cloth to connect the lintel to e.g. the rough frame.
- Void can be filled with straw, maybe some fixall.
- Then fix-all the exposed hardware cloth, so that plaster can stick to it.