Underfloor Heating (Wet Systems) RAMS: A Practical Guide for Plumbing & Heating Contractors

Table of Contents

• Why UFH RAMS Matter
• Key Hazards in Wet UFH Installation
• Manifold Installation and Pipework Connections
• Pipe Laying and Screed Preparation
• Pressure Testing Requirements
• What Your UFH RAMS Must Cover
• Frequently Asked Questions
• Next Steps

Why UFH RAMS Matter

Wet underfloor heating is installed across a wide range of project types — from new residential developments to commercial refurbishments and leisure facilities. Despite its relatively low-profile nature compared to high-risk trades like steelwork or roofing, UFH installation involves pressure systems, chemical exposure from screed and adhesives, manual handling of heavy manifolds, and coordination with other trades that must be documented in a compliant RAMS.

Under CDM 2015, UFH contractors are duty holders who must produce a project-specific RAMS before installation begins. On new-build residential projects, the principal contractor will typically require UFH RAMS to be submitted alongside plumbing and mechanical RAMS as part of the pre-commencement package.

This guide explains what a compliant underfloor heating RAMS must include, including the specific hazards that are most frequently missing from submitted documents.

Browse all trade RAMS templates on the RAMS AI trade hub — covering 22 specialist construction trades.

Key Hazards in Wet UFH Installation

• Manual handling of manifolds and controls — UFH manifolds, particularly multi-port commercial manifolds with actuators and controls, can be heavy and awkward to install at low levels. Manual handling risk assessments must address lifting from floor level, overhead fixing of manifold enclosures, and carrying manifold components through the building.
• Pressure testing hazards — UFH pipework must be pressure tested before screed is laid. Incorrect pressure testing procedure, use of compressed air in a water system, or testing above the pipe's rated pressure can cause sudden pipe failure and injury from water or air ejection.
• Chemical exposure from screed and adhesive products — Portland cement-based screed contains calcium hydroxide (alkaline), causing chemical burns on skin contact. Some UFH adhesive tapes use solvent-based adhesives. COSHH assessment is required for all chemical products.
• Trip and fall hazards from pipe layouts — UFH pipe laid in a serpentine or spiral pattern on the structural floor creates a significant trip hazard before screed is laid. The work area must be clearly signed and other trades prevented from walking on the pipe layout during installation.
• Working in incomplete structures — UFH is typically installed in new-build projects where the building structure is incomplete. Falls from incomplete floor openings, staircase voids, or unprotected edges must be addressed in the RAMS.
• Interface with screed contractor — UFH pipe must remain pressurised during screed laying to maintain pipe shape and detect damage. Coordination with the screed contractor is a safety-critical interface that must be specified in the RAMS.

Manifold Installation and Pipework Connections

Your method statement for manifold installation must specify:

• Manifold fixing — How the manifold will be fixed to the wall (bracket type, fixing centres, required fixing substrate) and at what height (typically 300-500 mm above finished floor level to allow pipe connections)
• Supply and return connections — How the manifold will be connected to the boiler flow and return pipework, including the compression or press-fit fittings to be used and the torque or tool requirements
• Actuator installation — Where zone actuators are installed, confirm that they are compatible with the manifold specification and that the wiring will be carried out by a suitably qualified person
• Commissioning valves and balancing — Specify that flow meters and commissioning valves will be set to achieve the specified flow rates for each zone

Pipe Laying and Screed Preparation

Pipe laying on the structural floor is labour-intensive and involves the following hazards:

• Trip hazard management — Specify that the pipe-laying area will be signed as a restricted zone and that other trades will be excluded during laying. After laying is complete and before screed, specify how the pipe layout will be protected from foot traffic (e.g., temporary walkway boards).
• Screed COSHH — Portland cement-based screed contains calcium hydroxide and is strongly alkaline when wet. Controls: waterproof gloves, safety boots (cement in boots is a serious chemical burn risk), eye protection, and washing facilities on site.
• Thermal break insulation — UFH insulation boards are laid under the pipe layer on the structural floor. Some products use polyisocyanurate (PIR) foam with slight respiratory sensitisation risk during cutting. Specify cutting controls (dust mask, ventilation).

Pressure Testing Requirements

UFH pipework must be pressure tested before screed is laid (as the screed encases and makes the pipework inaccessible after laying). The standard pressure test procedure for UFH systems:

• Fill the system with clean water
• Pressurise to 6 bar (or 1.5× the maximum working pressure, whichever is greater, subject to pipe manufacturer's maximum test pressure)
• Hold for 1 hour — record the pressure drop
• Reduce to working pressure and hold for 24 hours — record the pressure drop

Your RAMS must specify:

• No pneumatic (air) pressure testing — UFH pipework must be hydraulically tested with water. Air pressure testing of water pipework is prohibited because sudden pipe failure under air pressure releases far more energy than the same failure under water pressure, and can cause serious injury. This prohibition must be explicitly stated in your RAMS.
• Pump and gauge specification — The test pump must have a calibrated pressure gauge with an accuracy of at least ±5% of test pressure. The gauge must have a valid calibration certificate.
• Test attendance — The pressure test must be attended throughout. The test must be stopped and the cause investigated if unexpected pressure loss is detected.

What Your UFH RAMS Must Cover

• Scope: system type, pipe specification, zones, manifold locations
• Manual handling: manifold weights, lifting postures, mechanical aids
• Pressure testing: procedure, water-only requirement, pump specification, gauge calibration
• COSHH: screed (alkaline burns), insulation board cutting (dust), adhesive tapes (solvents)
• Trip hazard management during pipe laying and before screeding
• Screed contractor interface: pipe pressurisation during screed, coordination protocol
• Working in incomplete structures: floor openings, unprotected edges
• Emergency procedures and first aid location
• CDM pre-start briefing record

Frequently Asked Questions

What is the maximum test pressure for UFH pipework?

The test pressure is typically 6 bar or 1.5 times the maximum working pressure, whichever is greater. However, this must not exceed the pipe manufacturer's maximum rated test pressure — check the pipe specification before conducting the test. For most polybutylene or cross-linked polyethylene (PEX) UFH pipe, the maximum test pressure is typically 6 to 10 bar at ambient temperature.

How long should the UFH pipework remain pressurised after screed is laid?

UFH pipework should remain at working pressure throughout the screed-laying operation and until the screed has reached sufficient strength to protect the pipe from damage (typically 24 to 48 hours after laying). The screed contractor must be made aware that the system is pressurised, and any significant pressure loss during this period must be investigated before screeding continues.

Do we need a separate RAMS for the manifold commissioning once the screed is cured?

Commissioning of UFH manifolds — setting flow rates, purging the system, and commissioning zone controls — is typically carried out after the screed has cured (usually 28 days minimum for anhydrite screed). If the commissioning is carried out by the same contractor under the same RAMS, ensure the RAMS includes the commissioning phase. If commissioning is deferred to a different visit or a different contractor, a separate method statement for commissioning should be produced at that stage.

Next Steps

Your UFH RAMS should be reviewed for every project and updated to reflect the specific pipe specification, system pressure rating, and building environment. RAMS AI generates comprehensive UFH risk assessments pre-populated with the hazards and controls described in this guide.