Lowtech Graph lists low-tech options for every need of a home. Here you can compare them, find tutorials to build them, and link them together into a circular system. Why low-tech?
Elevated finished floor level
Passive · New build only
One of 3 ways to meet this need. Cost, carbon, footprint and rankings are relative to other solutions for the same need, not absolute.
What your site needs
Site with a known or projected flood/high-water-table risk
The ground floor built higher than the level floodwater or groundwater is expected to reach. The house sits on a raised base, so water can pass or rise around it without entering the rooms. It keeps floors, walls and belongings dry in a flood.
Matches structure lifespan (a design choice, not a wearing component)
Embodied carbon
Low
Space / material use
Low
Output timing
None
Skill to repair
None
Regulation (FR example)
Part of the structure or footprint: covered by the building permit (permis de construire) for a new dwelling. Rural sites are additionally constrained by the commune's PLU zoning, outside a constructible zone, a new dwelling is generally refused.
Levels are relative to the other options for this need, not absolute. Fewer dots is lighter.
Elevated finished floor level (This page) Can I use it? Not in a flat · New build only What does it cost me? Upfront cost: Low · Skill to build: Specialist · Upkeep: None · Change to daily life: None · Works without the grid: Yes Choose it if you are building new where water can rise, and want rooms that stay dry whatever the level.
Diversion swale / intercept ditch Can I use it? Not in a flat · No rebuilding needed What does it cost me? Upfront cost: Low · Skill to build: Basic · Upkeep: Light · Change to daily life: None · Works without the grid: Yes Choose it if you want the runoff from the slope above led around the house by a simple ditch.
Deflection berm (splitter wedge) Can I use it? Works in a flat · No rebuilding needed What does it cost me? Upfront cost: Medium · Skill to build: Intermediate · Upkeep: Light · Change to daily life: None · Works without the grid: Yes Choose it if you want a surge of water, mud or debris from uphill split before it reaches the wall.
We don’t list sizing or quantities, as the yield of each technique depends on the quality of its build. The catalogue compares options but doesn’t dimension them. Regulatory notes are indicative, with a French example, and need to be confirmed locally.