Contractors by the hour or quote the job

[Chris C.]

I did a quick search but didn't find a discussion about this.

How do you guys pay your contractors?

Do you guys let them quote the job knowing they need to pad it a little in case they mis-estimate the job?

Do you allow them to work by the hour? Could be better price IF they do not fudge the hours.

What do you guys do? My wife gets mad because I trust them to work by the hour. She thinks they should quote the job. She makes a good point so I am asking the experts.

Also, which ever method you use, how do you control them. With the hourly pay do you put a limit on the number of hours a job should take. If they need to go over they should call you. Any other ideas like this?