Damp Survey and Damp Proofing in Olney

Much of Olney's older housing is solid-walled: local limestone rubble, brick, or render over stone, bedded in lime mortar and built without a damp-proof course. These walls were designed to absorb and release moisture. The recurring causes of persistent damp in the town are therefore the things that stop them doing so, along with ground levels that have risen over the centuries so that pavement and yard surfaces now sit above internal floor level. Hard cement pointing, cement render on stone, modern impermeable internal finishes and rainwater goods discharging against a wall base account for the majority of what we find.

The Great Ouse and its flood plain define the lower part of the town, and properties near the river, the mill and the water meadows can be affected by a high water table, by surface water and, in the more serious events, by flood water entering ground floors and cellars. After a flood the important question is not whether a wall is wet but how wet, how deep the moisture has penetrated and how the structure is drying, because premature reinstatement traps moisture behind new plaster and finishes. We record moisture profiles at depth, advise on drying, and set out when reinstatement can safely begin.

Away from the historic core, the estates built from the mid-twentieth century onwards and the more recent development on the town's edges are cavity-walled and modern. Their problems follow the familiar modern pattern: cavities bridged by mortar debris or slumped retrofitted insulation, cold bridges at lintels and reveals, and condensation and mould where airtightness and insulation have been improved without matching moisture removal. Distinguishing that from a fabric defect takes half an hour of measurement and observation, and it decides whether the remedy is building work or a change in how moisture leaves the building.

Timber assessment carries particular weight in flood-affected and older buildings. Joist ends bearing into wet stone or brick, ground-floor timbers over damp sub-floor voids, and staircases and skirtings that have been submerged are all at risk of wet rot, and dry rot becomes a genuine possibility where timber stays damp in an unventilated space. Older roof structures frequently carry historic beetle flight holes that no longer represent live activity. We measure moisture content, identify the decay type where present, and state clearly whether structural members are affected.