Properties, especially London period properties are built to a tried and tested standard design. Changes to design from Georgian to between the wars were modest and incremental.
First owner complaints
If the design or construction was faulty, then the fault would have been rectified within the first year.
If the land was prone to high water because of local drainage or aquifer, the builders and planners would not have built on the land. They would have made a park out of it.
London heritage or period properties were largely built as terraces of houses. The terrace would have been subjected to considerable rain before being completed. There is no way they would have physically been able to build on the land if there was a high-water table.
All damp by definition results from change in use. Change include damage, weathering, alterations and changes to life stiles.
Therefore, it follows whatever has caused the damp, has caused it since the period in which this style of property was built.
- Start by identifying the keys changes from the original design, splitting into flats, change use of rooms or ventilation,
- Extension, whether loft, rear or side pose challenges, in particular sub-floor ventilation and rain water drainage,
- The painting or blocking of sub-floor vents can significantly reduce airflow and can cause rot.
- Painting, rendering or chemical damp proof course can significantly reduce a property’s ability to absorb and evaporate moisture, as it was designed to.
- Changes include modern lifestyle changes, such as showering regularly, drying clothes indoors, cooking.
- Blocking chimneys reduces the beneficial passive ventilation up flues. Capping without ventilation can cause problems.
- Consider the effect of weathering, damage to tiles, chimneys, flashing, soffits, facias, gutters, hoppers, downpipes, gullies, drains.
- Consider the rise in the garden height, whether through settlement, paving, concrete etc. It’s often worth looking at neighbouring properties.
- Anything the neighbour might have done, for instance a neighbour changing normal, permeable plaster, to impermeable plaster will change the capacity of the wall to evaporate moisture evenly on both sides. (Note it is a party wall agreement is required for chemical damp proofing, it’s not actually the chemicals that will cause neighbour problem, but the impermeable plaster).
- Other than Chemical Damp Proofing, one of the most heinous crimes against a period property is replacing a suspended wooden floor with a solid concrete floor, to make matters worse:
- plaster is allowed to touch the solid floor (absorbing moisture up the walls – not rising damp),
- sub-floor air flows to remaining timber is disrupted,
- membraned are not used and
- copper pipes are embedded into concrete and so corrode.
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