The problem is the customer is not happy so called the builder, he is now portraying himself as the 'helpful, friendly builder' against the 'big, bad powerwasher' who has damaged her patio.
He is telling her everything she wants to hear, she does'nt realise what he is saying is not unbiased, the only other option about who is to blame for the problem is him and no way has he even hinted at that.
His only get out is,..... i did it