A few thoughts.
The issue of the measure of damages is not that simple. People readily assume that the measure of indemnity should be the costs of repairing the defects. This is not always so. There are strong arguments to say that the measure of indemnity is the value of the depreciation caused by the negligence of the defendants but incorporating a reflection of the repair costs. I would approach the issue on the basis of claiming the repair costs
AND the measure of depreciation suffered. I suggest this as these are both losses that flow
naturally and directly from the negligence of the defendants. You can proceed this way legitimately without being pinged for seeking a double indemnity.
The question of jurisdiction arises. The way this has gone it is definitely a High Court case. Presently, the jurisdiction of the Circuit Court is €75,000. By issuing Circuit Court proceedings you waive the excess of your claim over €75,000. I understand your anxiety to get this sorted asap. However, you might not have to prejudice your position so easily. I assume that proceedings have not yet issued. I would instruct my solicitor to ask the defendants to consent to trial in the Circuit Court with unlimited jurisdiction. Alternatively, if they will not agree, I would issue High Court proceedings and then remit the case to the Circuit Court. Conventionally, High Court cases remitted to the Circuit Court are supposed to be tried with unlimited jurisdiction.
I am not attracted to the argument that says that you do not intend to leave the house in the near future anyhow. Respectfully, I think that this is false comfort, a gamble and a bad idea. Although there is no intention to move, the fact is that life circumstances can change unpredictably and you might find yourself needing to sell for reasons that you never imagined. In that scenario the ghosts of the history of the house will return and may bite badly. Whether you stay or go you still need to be "made whole" again for the full extent of your losses as that is actually your legal entitlement.
In relation to quantum I would be inclined to get two valuations of the house as it stands on the basis of full disclosure of
ALL of the problems and deficiencies. I think that would be interesting to give you a sense of what you have actually suffered in terms of loss of value. You will probably be advised by counsel to get this evidence which will be required anyhow to stand up the measure of this aspect of your losses.
And finally, whatever the insurance position, proceedings should be issued against
ALL parties involved with this affair. i.e. they should all be named as co-defendants.
I hope that this war comes to an end soon and that you will have some peace....