Hall of Water · Catalogue 15

🧪 The Moisture Lab

Watch water migrate through building materials via capillary action — the same force that makes a sponge soak up water and makes your walls draw moisture from the ground. See why rising damp happens, how high water can climb in different materials, and why a damp-proof course is the single most important thing in your wall.

Exhibit A · The rising wall

Capillary rise in building materials

Water table depth 0.5 m

Air humidity 65%

Wall thickness 225 mm

Time speed 1×

What you're seeing. A cross-section of a wall sitting on the ground. Water from the water table (blue zone at the bottom) is drawn upward through the material's pores by capillary action — surface tension pulling water into tiny gaps. The height water reaches depends on pore size: brick has fine pores (climbs 1.0–1.5m), stone has coarser pores (0.3–0.8m), and render can act as a wick pulling moisture even higher. The damp-proof course (DPC) is an impermeable barrier that breaks the capillary path.

Exhibit B · Material comparison

How high does water climb?

Capillary rise follows the Washburn equation: h = 2γcos(θ) / ρgr. Smaller pores (finer material) = higher rise. This is why lime mortar (large pores) is better for old buildings than cement mortar (fine pores) — lime lets moisture escape instead of trapping it. Modern buildings use a DPC (plastic or slate) at 150mm above ground level to block the path entirely.