You work and should get paid. It's always best to ask up front but still it's you're right. A job is a business deal, you provide work for money. Very simple, you worked, he owes you. You need to go talk to him about it, be polite, but also stand up for yourself.
Don't let yourself get down the road and take a chance on getting stiffed for your work. Also keep records for yourself of your hours too.