Doesn't an act of god fall within the criteria of Force majuer as with war and plague?
My point is that this spread of the virus and the disruption it would cause could be seen a mile off given what was happening in many other places and the reliance upon Force Majeure for breach of contract is a bit shaky, hence the reluctance for builders and construction companies to shut sites of their own accord.
Acts of God are unpredictable natural events such as storm, earthquake, flood etc. whereas Force Majeure is, human-initiated action that cannot be predicted or
controlled by the party to the contract. I think the word "controlled" is significant
At the moment, given government Rules, there is no reason or requirement for Builders to stop working. If the government went for a full hard lockdown, then I don't consider there would be any room for manoeuvring by any party to the contract to seek reparation from the other party.
However, if one party thought they had a legitimate case, there is no precedent, that I am aware of that covers the current set of circumstances, so if court proceedings were initiated the judge(s) would have to adjudicate, thus setting precedent for future similar actions.