Canadian helping a friend in the States work on his house

https://de.usembassy.gov/unpaid-work-is-work-make-sure-you-have-the-correct-visa/

Informal arrangements to work in exchange for lodging or meals are also considered unauthorized employment and are not permitted for tourists.

Temporarily suspending these rules for hurricane repairs would be big, big news and I never heard of any such even after the biggest calamities. Compassion is not in the job description of any immigration officers. They are just enforcing the rules, not making up any on spot. And the current USA administration has a proven xenophobic track record.

I am really trying to find a loophole but even if you were a carpenter or such and your friend would employ you so you could try to enter on a TN status under NAFTA

Not admissible as ST/Ts are persons intending to do work that is normally done by the construction trades (welders, boiler makers, carpenters, electricians, etc.) even where these trades are specialized to a particular industry (e.g. aircraft, power distributions, etc.)

Source: Can't find the original bulletin from 2002 on a gov site but this text is widely available, for eg http://www.ucalgary.ca/biztechlaw/node/300

Bummer. No TN for you.

Normally, any work that you do that could displace an American who could be paid to do that labor would be forbidden. So in normal circumstances, you couldn't do any type of construction work.

However, if you tell the border agent that you're coming to do volunteer cleanup work and staying at your friend's home, given the circumstances I don't think you would have a problem. However, this is really only valid for the next few weeks.