Contracts

[Daniel H.]

I recently signed a contract to have some work done on my buildings. I paid 50% upon signing the contract. Before even starting the job, the contractor is saying he talked to his engineer and the job is going to cost 25% more. What can I do here? The reason I signed the contract is because I liked the price quoted. I just can't go and say I don't like the price we agreed on, I have to pay you 25% less.

Advice on how to handle this situation? Also, how to prevent it from happening in the future?