Reply To: Moisture and concrete slabs

[Scott Willis]

Hi Sarah,
I don’t have knowledge of practice in your area of historic builds, but I suspect that like in many areas there was a wide variety of practice. A house over a patch of earth can effectively provide a dry cover, that, depending on ground water, can dry out the soil under the house for many metres deep – so even an uninsulated pad has the potential to provide passive thermal insulation, radiating down and up. This depends of course on how well drained the land is.
From what you describe, this is unlikely to happen. A house that suffers winter flooding and has a high water table sounds suspiciously like a house in an ‘at risk’ zone or hazard zone. Is it coastal, or near an estuary or beside a river?
If any of these things I would put it in the ‘problem’ basket. We don’t have any protocols for how to advise on these types of properties, but I suspect that this type of problem will pop up more and more and protocols will be necessary. Because if this is the situation there are issues around:
– Whether the house is in a zone that my be required to undergo ‘managed retreat as climate change becomes more pronounced;
– and,if this is the case, what sort of investment should be encouraged to maintain livability for the short/medium term?

Of course, I’m making some assumptions here. If I’m off track, you could simply advise digging drains all around the property to ensure water is drained away from the pad – this should be done if at all possible anyway.
Hope things are going well up your way?
Cheers,
Scott

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