Technical Library
Before You Build
Drawing checklist — what every build's drawing needs to show
The chapters above ran on assumed numbers wherever a real dimension wasn't available. Once a drawing carries the items below, a chapter can be rerun with real inputs.
- Overall dimensions: footprint and height (interior and exterior for anything that holds water)
- Member sizes: wall thickness, board sizes, post sizes, rebar sizes
- Spacing: rebar channels, bolts, posts, joists
- What it sits on: pad size, thickness, rebar, and the soil or slab beneath
- Materials: block weight, lumber species and grade, mortar or grout type
- Maximum load it will ever see: water depth, people, snow, whatever the heaviest day looks like
- Grout/dowel quality (Callister ch. 4): an ungrouted rebar channel or a loose bar isn't a composite — it's two materials near each other, and fails like unreinforced ceramic. Worth confirming on the drawing, not just assuming.
Materials data sheet — your materials, your table entries
The textbook's tables cover standard materials like lumber, block, and steel. Geopolymer, mortar, and papercrete aren't in any table, so their numbers have to come from testing. Each entry below is the equivalent of a handbook table value for your own material.
Geopolymer bricks and mortar
- Mix formula and cure process (time, temperature, moisture)
- Cured density: weigh a known-size piece, in lb per cubic foot
- Compressive strength: crush-test cubes at 7 and 28 days
- Bending strength: a small beam test, since water walls load the brick in tension
- Water absorption: matters for the cistern and Ogua
- Heat tolerance: for anything near a firebox or flue
Papercrete
- Mix, layering, and curing process
- Dry density and, if it will carry any load, a compression test
- Where it's used, and whether it carries load or only fills or insulates
Steel and lumber
- Rebar grade and source; if it's recycled or unmarked, treat it as lower-strength until identified
- Lumber species, grade, and treatment
- Fastener sizes and lag length
Sites
- Soil type where heavy things sit (the chapters assumed a default allowable bearing of 1,500 psf)
- Thickness and condition of any existing slab
Per build
- Intended use and the worst day it will ever see
- What happens if it fails, which sets how conservative to be
Geopolymer — published literature ranges (placeholders, not your tested numbers)
Lab-grade fly-ash/metakaolin geopolymer concrete, not Zach's specific mix — Callister ch. 2 quarters the low end of this range (~27 MPa) into a ~900 psi working stand-in for the Snawfus/Uktena/Ogua checks. Useful only for sanity-checking a real test result against ("is my number in the right neighborhood"), never a substitute for casting and crushing real cubes.
- Compressive strength: ~27–56 MPa (~3,900–8,100 psi), up to ~70 MPa (~10,150 psi) for well-designed mixes
- Flexural strength: ~6.2–6.6 MPa (~900–960 psi) at the 32–40 MPa compressive grades
- Splitting tensile strength: ~4.5–6.0 MPa (~650–870 psi), slightly higher than equivalent Portland concrete
- Density: Not well-reported in the sources checked; normal-aggregate geopolymer concrete generally tracks close to conventional concrete (~140–150 lb/ft³) unless a lightweight aggregate is used