In the interests of health and safety a number of trades are controlled by law, most particularly plumbing and electricity. The degree to which plumbing and electrical work are actually regulated varies from jurisdiction to jurisdiction. For instance almost all work performed in new construction must be undertaken by licensed plumbers and licensed electricians, and that right across the country. There are some exceptions to this general rule in different regions allowing for some work done in owner built homes to be done by the owner as long as it is inspected by the municipality.
THE OWNER-OCCUPANT EXCEPTION
In renovation, most jurisdictions require any work hired out to be done by licensed professionals but when the work is done by the occupant/owner (both occupant and owner, not the owners or occupants of rental properties) there are many exceptions. This exception is often restricted only to maintenance, changing same for same. Any additions or relocations in both electrical and plumbing still require licensed professionals or at least muncipal permits. In addition most general renovators will do minor electrical or plumbing work themselves, although they should technically be hiring a licensed tradesperson for that work. Some larger renovation companies actually have licensed staff on their in-house team.
Vancouver sits on one extreme where owner/occupants can take a course on such things as minor electrical work, get their permits and do it themselves. Ontario allows minor work like changing outlets and switches without any training as long as the owner/occupant obtains a permit. Quebec has decreed that changing a light bulb is as close as an occupant is allowed to get to any electrical wires. That is the technical side of the law and each jurisdiction seems to have arrived at their particular type of regulation via very different reflections.
Vancouver recognizes that people will do DIY electrical work anyway so they believe that a pro-active approach will have the end result of better work being done in real houses. However, a lot fewer people take the courses than purchase electrical fixtures and wiring at the renovation centres so just how effective is this approach is unknown.
Ontario believes that the permit requirement will allow the possibility of DIY electrical maintenance without opening the door too wide. But when the permits are more expensive than the light switches and there are no inspections, the general attitude is that this is just a government money grab and very few people get permits while there are a lot of switches sold in Ontario.
Apparently the Quebec absolute interdiction to touching electrical wires was pushed into place by the insurance industry trying to reduce house fires caused by electrical installations. At one point they tried to forbid the selling of all electrical wire and fixtures in retail outlets, restricting access to licensed professionals, but the courts judged that freedom of commerce prevailed and the retail stores could legally sell everything you need to build a house -- of course assuming you were purchasing it to give to your electrician to install it. Given the volume of electrical sales in the retail outlets, this policy has been a dismal failure with the consequence that an owner/occupant cannot even get his DIY installation inspected and rendered safe because he wasn't supposed to do it in the first place. Just to add total incoherence to the Quebec situation, Hydro Quebec advertises and subsidizes the retail sale of 240v setback thermostats directly to homeowners -- all of which are dangerous to work with without knowledge and none of which are legal for the homeowner to install themselves. It is fairly easy to get these 240v thermostats to work, but do you know if you have too many or too long wires jammed into that electrical box violating the electrical code fire safety provisions? This well functioning box could overheat and cause a fire! There is more to safe wiring than just making something go on and off.
DIY BOOKS AND THE LAW
DIY books abound on how to do all plumbing and all electricity. The books are legal, the activities they explain are illegal for non-licensed to do in some jurisdictions under some circumstances -- and that is usually noted in small print someplace in the book. As a DIY communicator should I follow the Quebec example of sticking my head in the sand, refusing to give any safety advice to people who are going to engage in this activity anyway? Or do I teach good practices but tell people in certain jurisdictions to not listen?
INSURANCE COMPANIES MAKE THEIR OWN LAWS
Sure you should follow the law where you live, primarily because you could potentially have an insurance problem if the house burns or floods and it is proven that you did illegal DIY work. But even where it is legal to do your own maintenance plumbing, insurance companies often attempt to lean on the NEW construction laws to refuse any payment. Where the work you have done was legal, the insurance companies cannot refuse payment unless they have written such restrictions into your policy. An insurance policy is a two party contract, and anything at all can be put into the contract, whether it is backed up by laws or not. For instance, most insurance companies today will not insure a hot water tank that is more than 10 years old. There is no law anywhere that requires you to change your hot water tank every 10 years. So the insurance companies are making unsupervised defacto laws since few of us want to live without insurance. Actually the manufacturers of hot water tanks are giving up on making quality tanks that could last much longer -- why bother if your insurance company won't listen -- so tanks today have half the steel thickness they had 20 years ago.
Did you really read the fine print of your insurance policy before going to the hardware store? You should. If your insurance policy says nothing about DIY work, then you need to check with your municipality as to just what is legal for you to do as an owner-occupant. If what you did was in fact legal in your jurisdiction, don't let the insurance company bully you. They often claim legal rights that they do not have to scare off payments.
My best advice is to study what you want to do. If you do not feel totally confident about what you are doing, either in plumbing or electricity (or the structure of the house for that matter) then call in a professional -- even if the laws in your area permit you to go ahead on your own. The laws are inconsistent, mostly ignored even by those who should be supporting or enforcing them, and the reality is that you or someone before you has probably already done a lot of DIY plumbing and electricity in your house. Learn to know if it is safe and healthy -- or ask a professional to inspect and correct it for you.