Timber frame infill is the surface that defines Cosgrove — historic stone cottages along the Grand Union Canal mixed with high-value waterside conversions — and here it carries canal-side mildew and dark fungal staining on humid brickwork, driven by canal-side humidity saturation, stagnant water bio-aerosols, and towpath silt abrasion. Canal and river confluence generates a zone of maximum atmospheric saturation. Canal and river convergence creates 100% humidity zones, saturating porous limestone instantly. Together they hold moisture and contamination against the fabric, which is why an unmanaged surface deteriorates rather than simply weathering. We answer that with deionised water at zero dissolved solids, applied from the ground through reach poles. The contamination is broken from the surface by ionic action and drawn out — no detergent, no pressure, no equipment touching the building. Canal-side humidity requires a consistent 8-weekly approach to prevent greening, with the freedom to book bi-annual resets for patios. Every visit is one fixed price, quoted before we arrive and fully insured — windows, gutters, fascias and solar panels included.