Building season runs roughly from the last frost to the first, and the disputes it produces surface months later: a leak in November, a warranty question in February, a subcontractor's lien notice arriving after the holidays.
By then the evidence is behind drywall and inside people's memories. The following costs nothing to collect while the work is happening.
Photographs of what will be covered up
The most valuable thing you can do, and there is a window of a day or two for each part of it.
Before insulation and drywall go in, photograph every wall and ceiling that is open. Get the plumbing runs, the electrical, the framing, the vapor barrier and any blocking. Stand in the doorway and take a wide shot of each wall, then close shots of anything that looks like a connection.
Two reasons. If something leaks later, knowing what is behind the finished surface saves an exploratory demolition. And if there is ever a question about whether work was done as specified, a dated photograph of an open wall settles it in a way nothing else does.
Do the same outdoors before backfilling around a foundation or covering a drainage line.
Change orders, even by text
Summer work generates changes constantly, and on a busy site they get agreed verbally over the noise of a saw.
The version that survives is short and written: what is being added, what it costs, and how many days it adds. A text message counts. What matters is that it exists, that it is dated, and that both people have it.
Keep them in one thread rather than scattered across a phone. When the final invoice arrives with four extras on it, a single thread answers the question in a minute, and a disagreement about the fourth one does not put the other three in doubt.
Who pulled the permit, and what the inspections found
Ask at the start who is pulling the permit and get the number. Work done under a permit is inspected, and those inspection results are a record made by somebody with no stake in the argument.
A homeowner who pulls a permit in their own name to save a fee takes on the responsibility that goes with it, which is a decision worth making deliberately rather than at a counter.
Keep the permit card and the final sign-off with the house records. It is the first thing a buyer's inspector looks for on work of any size, and the absence of it is what turns a completed project into a question at a closing.
Lien waivers with every payment
This is the one that catches homeowners who did everything else right.
In most states a subcontractor or supplier who has not been paid can place a lien against the property, even where the homeowner has already paid the general contractor in full. The remedy is a waiver: a short document signed by whoever received the money, releasing their claim for the work covered by that payment.
Ask for one with each progress payment, and a final unconditional waiver from the contractor along with waivers from any major subcontractor or supplier at the end. Contractors handle these routinely and are not offended by the request. The paperwork takes a minute and it is the difference between a paid job and a paid job you can prove.
The walkthrough list, made while the truck is still outside
Walk the work with the contractor before the final payment, with a notepad, in daylight. Write the list together, agree a date for each item, and both keep a copy.
Anything left off that list gets harder every week. A crew that is still in town returns for a morning. A crew that has started a job forty miles away returns when they can, which in September means October.
Warranty terms in writing, and what they cover
Ask for the workmanship warranty in a sentence: how long, what it covers, and who to call. Then collect the manufacturer warranties for anything installed, along with the model and serial numbers.
Register the products in the week they go in. Roofing and mechanical equipment frequently require registration inside a short window, and the difference between a registered and unregistered warranty is discovered years later at the worst possible moment.
The folder, which is the whole point
One folder for the project: the signed proposal, the change orders, the permit, the inspection sign-offs, the waivers, the photographs, the walkthrough list, the warranties, and the invoices with proof of payment.
It takes an hour across a whole summer, assembled as you go. What it produces is a project that can answer a question in January, and a set of documents that a buyer's inspector reads as evidence of a job done properly rather than a stretch of the house nobody can account for.