The person who comes to look at the damage is applying a document to a situation. They did not write the policy, they do not benefit personally from paying less, and they are working through a caseload that spiked the same week yours did if the cause was weather.
Approaching them as an opponent produces a worse outcome than approaching them as a professional who needs information. Approaching them as an ally produces a worse one still, because nobody in this process is representing your interests except you.
Who the adjuster actually works for
Three kinds, and the distinction matters. A staff adjuster is an employee of your insurer. An independent adjuster is a contractor the insurer hires, common after a widespread event when caseloads surge. Both work for the insurer.
A public adjuster is the third kind and works for you, for a percentage of the settlement. They are licensed, they are worth considering on large or complicated losses, and they are generally not worth the percentage on a modest claim. If you engage one, do it early rather than after a settlement you dislike, and read the fee agreement carefully.
What to do before they arrive
Document first, then mitigate, and do not wait for permission to stop further damage. Policies require you to take reasonable steps to prevent the loss getting worse, and the cost of doing so is usually recoverable. Water still running is not a reason to wait for an inspection.
Photograph everything, wide shots first, before anything is moved or torn out. Photograph the source of the problem and not only the damage. Keep every receipt for emergency work, tarps, fans, a hotel if the house is uninhabitable. And keep the removed materials, or at least a piece of them, since a section of soaked carpet pad or a length of failed supply line answers questions later that words cannot.
Then write the timeline. When it started, when it was found, what you did and when. One page, in order.
The walkthrough
Go with them. Not to supervise, but because you know the house and they do not. Point out the things that are easy to miss: the ceiling in the room below, the closet backing onto the wet wall, the cabinets that were already swelling.
Say what you know and say plainly when you do not know. Guessing about a cause is the most common way homeowners create a problem for themselves, because a speculative sentence about how long a leak may have been going gets written down and becomes part of the record. If you do not know how long, the answer is that you do not know.
Ask two questions before they leave. What is the process from here and when should you expect the estimate. And is there anything they need from you that they do not yet have.
Scope disputes and price disputes
When an insurer's estimate comes in below a contractor's, the difference is almost always one of two things, and they are handled differently.
A scope dispute is a disagreement about what work is necessary. The insurer's estimate replaces the drywall to four feet, the contractor says the wall has to come out entirely. This is the more common disagreement and the more resolvable one, because it is settled with evidence: moisture readings, photographs, a written explanation from the contractor of why the lesser scope will not work.
A price dispute is a disagreement about the cost of agreed work. These come down to local labor and material pricing, and they are usually narrower than they look. A contractor's itemized breakdown set against the insurer's line items generally shows the gap sitting in two or three specific items rather than across the whole estimate.
Sort which kind you have before arguing, because presenting a price argument to a scope problem gets nowhere.
When you disagree
Put it in writing, itemized, with the supporting documents attached. A supplement, which is a request to add to an existing claim, is an ordinary part of the process and adjusters handle them constantly. Damage discovered after demolition begins is the usual reason and it is expected.
If that does not resolve it, most policies contain an appraisal provision: each side names an appraiser, the two appraisers select an umpire, and the resulting decision settles the amount of the loss. It is faster and much cheaper than litigation and it is underused, largely because homeowners do not know it is in there.
Beyond that, every state has an insurance department that takes consumer complaints and has authority over licensed insurers operating there. That is a real channel and it is free.
The paperwork that shortens all of it
A claim file kept the way you would keep a job file. Every photograph dated. Every receipt. The timeline, updated. A log of every call with the date, the name, and what was said. Copies of every estimate from every direction.
Claims that go smoothly are overwhelmingly the ones where the homeowner could answer a question the same day it was asked. That is not luck and it is not charm. It is a folder, assembled in the first week, when everything is still fresh and nobody has started disagreeing about anything.