What is the Uniclass code for a roof leak detection system?

In Uniclass 2015 the system is Ss_75_50_50_96 Water leak detection and alarm systems, under Ss_75_50_50 Liquid detection and alarm systems (Systems table v1.43, July 2026). The sensing products sit under Pr_75_50_48 Liquid-sensing devices, including Pr_75_50_48_60 Pad leak sensors, Pr_75_50_48_47 Leak-sensing tapes and Pr_75_50_48_96 Water-sensing cables.

Where does roof leak detection go in an NBS specification?

Two places. The permanent leak detection system is its own system clause, classified Ss_75_50_50_96, with its extent shown on the roof drawings. The independent quality assurance of the waterproofing (inspection and integrity testing by someone who is not the installer) belongs in the roof waterproofing system clause itself, under execution and completion, because it is a check on that system. Keeping them separate stops the common error of specifying one and assuming you have the other.

Which roofs should have a permanent leak detection clause?

Any roof where the waterproofing will be covered: green, biodiverse and blue roofs, inverted roofs under ballast or paving, podiums, buried decks and landscaped roofs. Once the membrane is covered nobody can inspect it, so permanent detection is the only way to know it is leaking before the space below does. Also include it on exposed roofs over spaces that cannot tolerate water, on timber decks, and on refurbishments with a leak history. Every roof, covered or not, gets the independent quality assurance clause.

Is there a British Standard to cite in a roof leak detection clause?

There is no British Standard for permanent roof leak monitoring. Cite the standards that govern the surrounding work: BS 6229:2025 clause 6.2 for integrity testing before temporary protection and after its removal, NHBC Standards 2026 Chapter 7.1 for integrity testing on warranted homes, BS 8102:2022 section 6.5 Note 2 for buried decks, CIRIA C817 for blue roofs, LRWA Guidance Note 18 for electronic testing of liquid-applied membranes, and ASTM D7877 and D8231 for electronic leak detection methods.

Should a leak detection clause name a product?

Usually not. A performance clause that fixes position in the build-up, power and penetrations, zone resolution, service life, commissioning and alarm ownership lets several systems compete and protects what matters. Name a product only where the client has a reason to standardise, and then include an or-equivalent route with the same performance tests.

What should the integrity testing clause say?

Write it as independent quality assurance of the waterproofing. State the method or methods (low-voltage or high-voltage electronic testing, or visual inspection with seam probing where the membrane is not electronically testable, agreed with the designer at Stage 3), require inspection and testing by a tester independent of the installer who reports to the Employer, require it before temporary protection is installed and again after it is removed in line with BS 6229:2025 clause 6.2 and before any overburden is placed, require all defects repaired and retested, and require a report with photographs. On NHBC-warranted homes the report must be available to NHBC and the method must appear in the design information. Do not accept a conductive underlay as a substitute for a build-up that can be tested.

NBS Specification for Roof Leak Detection: Uniclass Codes and Model Clause Text

In an NBS specification, a roof leak detection system is classified under Uniclass 2015 as Ss_75_50_50_96 Water leak detection and alarm systems, and is best written as its own performance-based system clause, separate from the independent quality assurance of the waterproofing, which belongs in the roof waterproofing clause. This page gives the codes, says where each piece goes, and provides model clause text in the NBS system-clause shape you can adapt.

The rule for when to include each: every roof gets the quality assurance clause; any roof where the waterproofing will be covered (green, blue, inverted under ballast or paving, podium, buried, landscaped) also gets the permanent leak detection clause, because a covered membrane cannot be inspected. The decision in full is in should you specify leak detection in this roof?.

The reasoning behind each requirement — position, power, zoning, service life, commissioning and alarm ownership — is set out in how to specify a smart, integrated leak detection system in a roof build-up. This page is the drop-in version.

The Uniclass codes

Table	Code	Title
Systems	Ss_75_50_50_96	Water leak detection and alarm systems
Systems (parent)	Ss_75_50_50	Liquid detection and alarm systems
Products (parent)	Pr_75_50_48	Liquid-sensing devices
Products	Pr_75_50_48_60	Pad leak sensors
Products	Pr_75_50_48_47	Leak-sensing tapes
Products	Pr_75_50_48_96	Water-sensing cables

Source: NBS Uniclass 2015, Systems table v1.43 (July 2026). Ss_75_50_50_96 replaced the older Ss_75_50_28_96 and Ss_75_50_33_96, which are no longer in use — worth checking if you are working from an older specification. Uniclass maps it to NRM1 5.12.1 (Communication systems); agree with your cost consultant where it is carried.

A battery-powered sensor array is closest to Pr_75_50_48_60 (pad sensors). A conductive grid or tape system is closest to Pr_75_50_48_47 (leak-sensing tapes).

Two clauses, not one

What you are specifying	Where it goes	Why
Permanent leak detection system — sensors or grid, monitoring, alarms	Its own system clause, Ss_75_50_50_96, with extent on the roof drawings	It is a separate system with its own products, power, commissioning and owner
Independent quality assurance of the waterproofing — inspection and integrity testing by someone who is not the installer, before cover and at completion	The roof waterproofing system clause, under execution and completion	It is a check on the waterproofing, done by a tester who reports to the Employer, at defined points in the programme

The common failure is a single line — “integrated leak detection to the roof” — that leaves the tenderer to decide whether you meant a test, a system, or both. A well-specified roof that will be covered has both: the independent QA proves the membrane was sound when it was covered; the system reports what happens afterwards. See permanent monitoring vs electronic integrity testing.

Model clause 1 — permanent leak detection system (Ss_75_50_50_96)

Adapt bracketed values. Written as performance requirements so that more than one system can compete.

Ss_75_50_50_96 Roof leak detection and alarm system

Description: Permanent leak detection system integrated within the roof build-up, to the monitored extent shown on drawing [ref].

System outcomes

Detects water entering the roof build-up through the waterproofing, and reports the affected zone, for the design life of the waterproofing without intervention.

Raises an alarm to the nominated recipient(s) within [24] hours of a detection event.

Provides a dated record of readings from commissioning onwards, owned by the Employer and exportable in an open format.

System performance

Monitored extent: [all roof areas over internal occupied and plant spaces], as hatched on drawing [ref]. Areas over external space: [excluded].

Localisation: [state either] detected water localised to a zone of not more than [ ] m² / breach located to a cell of not more than [ ] m².

Service life without intervention: not less than [25] years or the warranted life of the waterproofing, whichever is greater. Submit evidence of service life [from an accredited test laboratory where available].

Penetrations: no penetration of the vapour control layer or the waterproofing by sensors, cables or fixings, unless detailed and approved by the waterproofing manufacturer in writing.

Compatibility: confirm suitability for the specified build-up, including membrane type, deck and overburden. Where the system relies on electrical conductivity across the membrane, confirm the build-up provides a conductive path (note limitations on black EPDM, foil-faced layers, isolated decks and timber decks); a conductive underlay added for this purpose is not accepted as a substitute for a compatible system.

Data: Employer owns all data; export as [CSV / API] available for the life of the system; state the arrangements if the monitoring service ends.

Products

Sensors / sensing layer: [Pr_75_50_48_60 pad leak sensors / Pr_75_50_48_47 leak-sensing tapes], manufacturer’s standard, or equivalent meeting the performance above.

Gateways / control equipment: located and powered as shown on drawing [ref].

Execution

Install in sequence with the roof waterproofing, to the manufacturer’s instructions and the approved layout.

Record each sensor or zone on the roof plan as installed.

Commission before the waterproofing is concealed, and only after the waterproofing has passed independent quality assurance (see roof waterproofing clause).

Record baseline readings for every zone at commissioning.

System completion

Submit: zone map; as-installed sensor positions; baseline readings; alarm route and named recipient(s); response period; written confirmation from the waterproofing manufacturer that the system does not affect the waterproofing guarantee.

Include in the building owner’s manual, with the party responsible for monitoring and response after handover.

Model clause 2 — independent quality assurance of the waterproofing (in the roof waterproofing clause)

Insert under execution and completion of the roof waterproofing system clause. The standards call this integrity testing; the clause makes the independence explicit.

Independent quality assurance of waterproofing

Inspect and test the waterproofing for integrity by [low-voltage electronic leak detection / high-voltage electronic leak detection / both], carried out by a tester independent of the waterproofing installer and the membrane manufacturer, appointed by or reporting to the Employer [and a member of RAWTA or demonstrably equivalent].

Where the membrane cannot be tested electronically (for example black EPDM or foil-faced bitumen, or where the deck is electrically isolated), carry out the alternative method agreed with the designer [visual inspection with seam probing / flood test / other]. A conductive underlay is not accepted as a means of making an otherwise untestable build-up compliant with this clause.

Timing: before temporary protection is installed, and again after it is removed, in accordance with BS 6229:2025 clause 6.2; and before any overburden, paving, green roof or blue roof components are placed.

Repair all defects and retest. Do not conceal the waterproofing until it has passed.

Report: test method, extent, defects found and repaired, retest results, photographs, and the tester’s competence. [On NHBC-warranted homes: make the report available to NHBC, and state the test method in the design information, per NHBC Standards 2026 Chapter 7.1.]

Liquid-applied systems: test in accordance with LRWA Guidance Note 18.

What to cite, and what not to

Cite with confidence

BS 6229:2025 clause 6.1 (electronic leak integrity testing among the compliance tests to agree) and clause 6.2 (test before temporary protection and after removal). Neither names independence; the independence requirement is yours to write.
NHBC Standards 2026, Chapter 7.1 — integrity testing on roofs over 50 m² or hard to access, report to NHBC; green roofs tested before covering; test method in the design information.
BS 8102:2022 §6.5 Note 2 — accepts warm roof build-ups and loose-laid waterproofing on buried decks where permanent leak detection is employed such that leak locations can be identified and repairability is achieved.
CIRIA C817 §3.2.3 — on warm blue roofs, a permanent leak detection system should be considered.
LRWA GN18 — electronic integrity testing of liquid-applied membranes.
ASTM D7877 and ASTM D8231 — electronic leak detection methods (D8231-24a supersedes D8231-19).

Treat with care

“Compliant with ASTM D8551.” D8551 covers permanent monitoring of geomembranes in containment — ponds, landfills, tanks — not building roofs, and it expressly declines to cover moisture-detection systems. Ask what the claim means before accepting it.
Any claim that a standard requires permanent monitoring on your roof. No UK standard or warranty body that we know of does. What NHBC requires, and BS 6229:2025 recommends, is integrity testing. The case for permanent detection on a covered roof is a design argument, not a compliance one, and it is a strong one.
A conductive underlay offered to make a build-up testable. Our view is that it adds little, and on an inverted roof, where the membrane already sits on concrete, nothing. If the build-up cannot be tested, change the build-up or agree a different QA method.
Service-life claims of 20–30 years. These are calculations. Ask what reporting interval and signal conditions they assume.

Start here if you are deciding whether this roof needs leak detection: Should you specify leak detection in this roof?
Start here if the roof feels high-risk: High-risk flat roof? How to reduce the risk
How to specify a smart, integrated leak detection system in a roof build-up — the reasoning behind each clause
What are the best smart roof leak detection systems? — the systems on the market
Electronic leak detection — the complete UK guide
How many leak sensors does a roof need?

Vector will mark up your roof waterproofing and leak detection clauses as part of a waterproofing design review. Send us the specification.