Some home remodeling projects are very simple and may not need the services of an engineer, architect, contractor, and other such professional; if you're tearing down a wall that you know is not load-bearing or are putting up a wall to split one room into two, you may be able to do this on your own. However, some home remodel and renovation plans should involve consulting with an engineer, and not just an architect or contractor. Note when this is so you know your plans for your home are safe and will last for many years to come.
The home's foundation
If you're thinking of underpinning the foundation, pouring a new part of the foundation for an add-on, or otherwise doing anything that would affect the foundation itself, you want to call an engineer. It's important that your current foundation be examined for cracks and damage before you do any work to it, to ensure it can support the work you're planning, even underpinning. Adding a wing or new sunroom to your home means more weight on the foundation, even if you pour a new foundation for this addition. In all these cases, a structural engineer should be called to examine the foundation and note any repairs to be made and if your plans can be supported properly.
As with the home's foundation, you need to ensure you're making the right decisions when it comes to changes you might make to the home's framing. Tearing out an exterior wall, even if you expand your home, can mean putting added weight on other areas of the home and, in turn, having the framing crack and warp. Remember that exterior walls are built differently than interior walls and they are meant to carry more weight, so pulling down an exterior wall and then adding new walls inside may not be sufficient for supporting your home's weight overall.
You may not realize that the roof of your home actually helps to manage the weight of the home itself; the beams and rafters of a roof disperse this weight across the home's frame, so that no one side of the house is holding more weight than it should. If you're thinking of making any changes to the home's roof, such as going from a standard stick-built roof to exposed timber beams, you want to ensure an engineer has been consulted to know the safest way to do this, and ensure your new roof can hold up the home as it should.