In-Screed UFH in a Bromley Extension

The Brief

A Bromley homeowner was adding a kitchen-diner extension to the rear of the property and had committed to an air source heat pump as the primary heat source. That made in-screed underfloor heating the right choice for the extension. The builder had the slab down, PIR insulation specified at 100mm, and a screed schedule pencilled in for the following month. Our job was to design the UFH layout, co-ordinate with the heat pump installer, and hand over a pressure-tested system ready for the screeder.

What We Did

• Worked from the architect's drawings: Designed the pipe layout to suit the extension's heat-loss profile and the heat pump's design flow temperature (38°C at worst case), with pipe centres at 150mm under the glazing and 200mm elsewhere.
• Fitted perimeter edge insulation: 8mm foam strip tight to every wall before any pipe went down, allowing the screed to expand cleanly.
• Clipped 16mm PE-RT pipe to PIR: Clipped the pipe to the PIR insulation with UFH clips, laid to the designed layout, and tails brought back to the manifold location in the utility.
• Sized and fitted the manifold: 3-zone manifold with flow meters and actuators on each loop, sized for the extension plus a connection spare for a future conservatory.
• Pressure-tested the system: Leak-tested to 6 bar, held for 24 hours, documented and left under pressure for the screeder.
• Provided a commissioning schedule: 28-day wait after screed pour, then a graduated heat-up schedule in writing for the heating engineer to follow at first start.

The Result

A pressure-tested, properly designed in-screed UFH system ready for the screeder to pour, with no surprises for the heat pump installer and clear documentation for the homeowner. The extension now has even heat across the whole floor, pairs beautifully with the low flow temperatures the heat pump wants to run, and is covered by a 50-year pipe manufacturer warranty.

Duration: Two working days on site for the UFH install, plus design and survey beforehand.

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