Depending on the nature of the work, there will be a high or low chance of the contractor needing to make good adjacent walls/roofs/plaster/fences/paving etc. There is always a risk. And under any contract, it’s always best for the party most able to deal with risk, to manage that risk.
Now, if you don't include a clause to deal with this, that creates two main issues for a client - the first is that the costs are unknown and there is an element of ransom for the client should damage occur, secondly the contractor is under no incentive to prevent or minimise damage - in fact it’s the opposite and to his advantage to cause damage for which he will be paid to rectify, at a price of his choosing.
So the normal thing is to instruct the contractor to allow for any damages within his pricing. He knows about the work, what may get damaged and how things will be done and the associated costs, so should manage this risk by building in a factor if he feels it necessary
What the contractor then does, is include an allowance to pay for any damages that he thinks he may cause or may be necessary. Under a competitive tender the contractor is incentivised to keep these potential costs down and not inflate his price, else he could lose the work.
One way or another the client will be paying for the damages – either directly or as a factor within the tendered price. But having the contractor manage this risk is the most efficient and cost effect way for both parties. If the contractor then causes no damage, he is quids in.
