Formula & constants
Premises liability turns on whether the owner exercised reasonable care and had notice of a defect. Vertical changes over ¼ inch are the threshold where a surface irregularity becomes both an ADA and a trip-hazard concern, most commercial lots need restriping every 18–24 months, and documented inspection and repair logs are the strongest available defence. All default values are editable — when your supplier's data sheet or local code says otherwise, use that number.
Where this fits in your project
This tool is one step in a bigger job. Once you have these numbers, ada parking compliance calculator (ADA Parking Compliance Calculator), then pavement maintenance budget calculator (Pavement Maintenance Budget Calculator). For the full sequence see the project workflows, compare approaches on the comparison pages, and check local factors in the state guides.
Frequently asked questions
What counts as a trip hazard on pavement?
A vertical change greater than about a quarter inch. Beyond that threshold a surface irregularity becomes an accessibility and liability concern, and it is the most commonly cited pavement defect in claims.
How often should a parking lot be restriped?
Every 18 to 24 months for most commercial lots. Faded striping is an inexpensive fix that is easy to overlook and commonly cited — including on accessible spaces and access aisles.
Does documentation actually reduce liability?
It is the strongest practical defence. Scheduled inspections, dated photographs and repair records demonstrate reasonable care and notice handling far better than any verbal account of routine maintenance.
What is the highest-risk winter gap?
An undocumented snow and ice protocol. Having no written procedure and no service log leaves an owner with little to show that reasonable care was exercised before an incident.
Is this calculator legal advice?
No. It is an informational risk-screening tool. Premises liability standards vary by state and by the injured party's status on the property — consult a licensed attorney in your jurisdiction for advice on a specific situation.
Last verified: — See our methodology.
Planning estimates only — confirm quantities with suppliers and local code before ordering.