Traditional buildings don't fail because they're old — they fail when modern materials and methods get used on them without accounting for how they're built. Most of the maintenance decisions that matter for a pre-1919 home come down to one question: does this let the building keep breathing, or does it seal it up?
Repointing
Lime mortar is softer and more porous than modern cement mortar. On a solid-wall building, lime pointing allows moisture to evaporate through the joints rather than being forced through the brick or stone itself. Cement pointing is harder than the masonry around it — it can trap moisture and, over time, cause the masonry itself to spall and decay.
Render & plaster
The same logic applies internally and externally: lime render and lime plaster breathe, cement render and gypsum plaster largely don't. Replacing lime with cement is one of the most common causes of damp appearing in a period home that never had a problem before.
Timber
Timber built into a solid wall — joist ends, lintels, structural beams — relies on the wall around it staying able to dry out. Sealing a wall with impermeable materials raises the risk of trapped moisture reaching timber and causing rot, even where the timber itself was never the problem.
Ventilation
Traditional buildings were often designed with more incidental ventilation than modern airtight construction — open chimneys, suspended timber floors with underfloor airflow, ill-fitting original windows. Draught-proofing and floor insulation done without care can remove ventilation the building was relying on, shifting moisture problems elsewhere.
The general rule
Before any repair or upgrade — repointing, render, insulation, floor works — the question worth asking is whether the material or method lets the building continue to manage moisture the way it was built to. If it doesn't, it's worth understanding the trade-off before committing.