Local Law 31 changed the lead paint compliance regime in NYC in a way owners are still adapting to. The requirement to perform XRF testing on every unit in pre-1960 multifamily buildings was originally due August 2025, and HPD enforcement has been ramping up since. If you own pre-war multifamily and you don't have XRF certificates on file, you have an exposure problem.
The short version
LL31 amended Local Law 1 of 2004. The headline change: every dwelling unit in a multifamily building constructed before 1960 — and post-1960 buildings the owner has reason to believe contain lead paint — must be tested for the presence of lead-based paint using XRF technology. The owner is responsible for arranging the testing, paying for it, and maintaining the certificates.
The original deadline for the bulk of the housing stock was August 9, 2025. HPD's enforcement strategy has been graduated:
- 2025: outreach and education.
- 2026: active inspection sweeps and violations on identified non-compliant buildings.
- 2027 and beyond: full enforcement, including referrals to housing court for repeat violators.
If you got an HPD inspection in 2025 and the inspector asked for your XRF reports, you got a free pass. In 2026 the same inspection generates violations.
What XRF actually does
XRF stands for X-Ray Fluorescence. The technology bombards a painted surface with low-level X-rays, which excite the metals in the paint and generate a fluorescent signature. A detector reads the signature and reports the lead content in milligrams per square centimeter.
The threshold for "presence of lead paint" under HPD rules is 1.0 mg/cm². Anything at or above that is positive. Anything below is negative — but the inspector should report it as "below threshold," not "lead-free," because trace amounts may still be present.
The advantages of XRF over older test methods:
- Non-destructive. No paint chips removed. No damage to the surface.
- Fast. A typical reading takes a few seconds. A skilled inspector can test an entire two-bedroom apartment in 60 to 90 minutes.
- Comprehensive. Every painted component can be tested — walls, doors, windows, trim, radiators, ceilings.
- Reportable per component. Each test gets logged with location, surface, color, and result. The output is a defensible document.
What it doesn't do
XRF is a presence test, not a hazard assessment. It tells you whether lead paint exists; it does not tell you whether it is in a deteriorated condition that creates a hazard. That is why dust wipe tests still exist and are still required separately.
If your XRF report says "negative throughout the unit," your lead paint compliance just got dramatically simpler. If it says "positive on six surfaces," you now have an active hazard management obligation under HPD's existing rule, including dust wipes after any disturbance, lead-safe work practices, and tenant disclosures.
XRF versus dust wipes
These are different tests doing different jobs. Owners conflate them constantly.
XRF tests the paint itself. Performed once per unit (and again after major work that changes finishes). Tells you what is in the building.
Dust wipes test surface dust for lead loading. Required after any work that disturbs lead paint, after a tenant turnover in a unit with positive XRF, and at HPD's discretion. Tells you whether the management of lead in the building is keeping the dust below hazardous levels.
You need both. XRF is the foundation. Dust wipes are the ongoing operational test.
The testing process for a single unit
A compliant XRF test of a unit looks like this:
- Inspector arrives, certified as an EPA-accredited Lead-Based Paint Inspector. Verify the credential.
- Notice given to occupant in advance. HPD requires the owner to provide reasonable notice and offer accommodations if the unit is occupied.
- Component-by-component testing. Every painted component, every room. Inspector logs each reading.
- Calibration checks at the start, middle, and end of the day, against a known standard.
- Report generated: a per-component table with locations, results, and any positives flagged. Photos optional but recommended.
- Owner receives the report (the LL31 Inspection Report and Certificate). Stored permanently.
A typical NYC apartment costs $200 to $500 to test in 2026. A 50-unit building in a single visit can run $8,000 to $15,000 with a discount for volume.
Common mistakes
Testing a sample of units rather than every unit. LL31 is unit-by-unit. Sampling does not satisfy the rule.
Forgetting common areas. Hallways, lobbies, stairwells, mechanical rooms — anywhere children might be present needs testing too.
Letting the inspector skip components. Some inspectors race through and test obvious surfaces. The rule says every painted component. Closets, behind doors, window troughs, radiator covers — all required.
Storing the certificate badly. This is a permanent record. Cloud storage, organized by building and unit, with backups. A lost certificate after enforcement starts means re-testing, plus violation exposure for the gap.
Not updating after renovation. If you gut-renovate a unit, the original XRF is no longer valid for the surfaces you replaced. Re-test those components.
The cheapest way to do LL31 is to do it once, do it correctly, and store the records well. The expensive way is to do it cheaply with a marginal inspector, then redo it after HPD asks questions.
What HPD enforcement looks like in 2026
Inspectors are visiting buildings on the basis of:
- Pediatric lead poisoning case reports cross-referenced to building addresses.
- Tenant complaints to 311.
- Routine HPD inspections that escalate.
- Targeted sweeps of known high-risk inventory.
When the inspector arrives, they ask for the XRF reports for the unit being inspected and for any cited unit. If you can produce them, the inspection focuses on visual condition assessment. If you cannot, you get a violation for failure to test plus whatever conditions were observed.
Penalty escalation is sharp. The initial violation is moderate. Continued non-compliance triggers Class C "immediate hazard" violations, and HPD has authority to perform the testing themselves and bill the owner — at premium rates.
Workflow for owners
Practical sequence if you are behind:
- Inventory pre-1960 units. Pull DOB records or PLUTO. Confirm the year of construction.
- Pick a contractor. Verify accreditation and experience. Get prices for the full inventory in a single engagement; volume drops the per-unit cost.
- Schedule with tenant notice. Two-week notice is standard. Plan for some unit access challenges.
- Test, document, store. Every certificate filed with the building's records.
- Build a remediation plan for any positives. Lead-safe work practices, ongoing dust wipes, tenant disclosures, EPA RRP-certified contractors for any disturbance.
For owners with portfolio-wide pre-war multifamily, the LL31 trail — units tested, units pending, certificates on file, dust wipes scheduled — is exactly the kind of record LLDesk keeps coherent across hundreds of units.
Key takeaways
- LL31 requires XRF testing of every unit in pre-1960 multifamily buildings. The headline deadline was August 2025, and 2026 enforcement is active.
- XRF is a non-destructive presence test for lead paint. Dust wipes are a separate, ongoing test for lead in surface dust. You need both.
- A compliant test covers every painted component in every unit and common space. Sampling does not satisfy the rule.
- Store the certificates permanently. Lost certificates mean re-testing plus violation exposure.
- A positive result triggers an active hazard management obligation, not just a one-time disclosure.