Market value is not an accounting entry, cost is what matters.
Create an Other Expense account called fire loss, and an Other Income account called Fire loss income
When the building is complete and ready for occupancy ...
Journal the accum depreciation to the fixed asset account, then journal the fixed asset account to the fire loss expense account
Then journal the capex fixed asset account to the fire loss expense account, and if there is accum depreciation associated with the capex account first journal that to the capex account
Journal the insurance payment to the fire loss income account and a new fixed asset account for the property.
Journal the old land fixed asset account to the new land fixed asset account
Property should be set up this way as fixed asset accounts IMO
address of property
>> >> accum depreciation building