Much of the work of a surface remodelling can be done by homeowners with little or no experience, but there are areas where they should consider expert help. Electrical work is often dangerous, and it should be left to those who have been properly trained. They are well aware of the risks they are taking, and their expertise will keep the home safe and able to pass the building codes.
Plumbing has long been an area many people have chosen to contract expert help, but it depends upon the work that needs to be done. Many homeowners would rather hire a licensed plumber for the most complicated jobs, but few of them realize how quickly even a simple job can become difficult. Hiring an expert to help them assess their needs in the first place could help them know whether or not they will find it above their head if they do it on their own.
It's popular to DIY a security system using modern WIFI enabled CCTV and 3G connected intruder alarms but many prefer security to be professionally installed and maintained by experts of have decades or experience.