Hiring Your Contractor - get it in writing!
It’s important to make sure that you get everything that you agree to with your contractor in writing. Really! Every little detail, every change, even the details of the types (and sometimes colour) of materials. This can be done with appendices to your main contract.
There are a lot of shady people who seem to gravitate towards fields where people aren’t educated about the issues involved, and one of these areas is construction. I won’t talk about mechanics and law. You have to protect yourself, and the best way to do this is to make sure that you have everything in a contract. Cover the basics in your main contract (available here), and use addendums or appendices to cover anything unusual or any specific details, such as material lists, unusual timelines, change orders, and so forth. (I’ll be posting a copy of a change order form you can use later).
When you’re doing the contract, it’s best to have an impartial witness available, at least for your part. If any of your contractors are incorporated (they are, aren’t they?) then a corporate seal holds up in courts to the same effect that a witness does. So, they can use that in lieu of a witness. Don’t really stress about that, since in most jurisdictions (even in the USA) the contract is still binding, whether there are witnesses or not. This just makes it easier to prove, should you have to. And I hope you never will have to!
Remember, if it isn’t written down, it wasn’t agreed to!