Instead of spending money to have a gutter company install, uninstall, and then reinstall your system, hire the roofing and siding company first. The simple answer is that if you are replacing both, you should start with the coating. This is because the two are attached to each other, and if you first replaced the gutter, you'll need to remove the new gutter and then replace the liner. Ultimately, if you can replace both at about the same time, this is the easiest solution.
The reality is that both are potentially hazardous jobs involving work at height, and it would be typical to use a contractor who can carry out a meticulously planned gutter installation. In addition, removing the gutters will help ensure that the roof edges are properly sealed and properly installed. When replacing or repairing the roof, it's a good time to remove the gutter system and inspect it thoroughly. Whether we like it or not, the gutter system is being abused quite brutally and some repairs are likely to be needed.
Now that we have established that, in almost all cases, the gutter system must be removed during a roofing change process, the next logical question is whether or not the gutters should be replaced. When a valley stops in the middle of a roof, it will have a gutter that flows into it so that water can continue to flow downward. Rainwater flows through the channel created by the gutter and eventually to the ground, avoiding your home. With that in mind, your roofing contractor should not remove the gutters during roof replacement.
Both products are usually made of vinyl or PVC these days and will eventually need to be replaced. Roofing and gutters are two completely different art forms that require different skills and tools. It is important to perform at least annual maintenance on the gutters to clean and check them. When that gutter in the valley is filled with leaves and other debris, one of the most common roof leaks occurs.
The gutter is the system by which rainwater is allowed to flow out of your home safely, without damaging the property.