In most states, if your contract does not cover this subject, the risk of loss is on the seller. In other words, if the building is damaged by fire before the closing, the buyer can cancel the purchase unless the seller restores the building to its prior condition.
Since this is an important issue, it is best to cover it in the contract rather than to rely on the prevailing law. You and the seller can tailor this term to meet your own needs and wishes. In case of a legal dispute, a judge or arbitrator will make every effort to carry out the intentions of the parties as stated in the contract.