U-value of a beam and block floor with PIR

The new-build suspended concrete floor: beam & block, PIR, screed.

A beam-and-block floor with 100mm PIR under a 75mm screed typically achieves a U-value of about 0.13–0.15 W/m²K calculated to BS EN ISO 13370 for a typical dwelling footprint — comfortably meeting the 0.13 notional with the standard spec. It is the default suspended floor of volume housebuilding.

Open this build-up in U-Monkey — pre-filled, free

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The build-up (outside → inside)

The pre-filled link opens with U-Monkey’s default footprint (P/A 0.6) — edit to your floor.

Typical U-values for this construction

SpecificationU-value (W/m²K)Notes
100mm PIR + 75 screed, typical semi≈ 0.13–0.15Standard new-build spec
150mm PIR (larger or exposed floors)≈ 0.10–0.12FHS-comfortable

Figures computed with the BS EN ISO 6946 combined method (bridging included) using BR 443 conventional lambda values — indicative for the generic build-up shown. Your products, thicknesses and (for floors) footprint will move the number: that's what the calculator is for.

What changes the number

As with all ground floors, perimeter-to-area does the quiet work — check the same spec on your actual footprint. Edge insulation and the wall-floor junction detail (a ΨMonkey job) decide how much of the paper performance you keep.

Next: check the junctions

A U-value covers the flat area of an element — but heat also escapes where elements meet, and at modern U-values those junctions can be 20–30% of a dwelling's fabric heat loss. Now you know your U-values, model the junctions with the free ΨMonkey psi value calculator (no subscription; PDF reports £15 +VAT):

Or read thermal bridging explained to see how junction Ψ-values feed your SAP calculation.

Frequently asked questions

What is the U-value of a beam and block floor with PIR?

A beam-and-block floor with 100mm PIR under a 75mm screed typically achieves a U-value of about 0.13–0.15 W/m²K calculated to BS EN ISO 13370 for a typical dwelling footprint — comfortably meeting the 0.13 notional with the standard spec. It is the default suspended floor of volume housebuilding.

Does the insulation go above or below a beam and block deck?

Above, almost always — rigid boards over the deck, screed or chipboard over the boards. It keeps the insulation continuous and the calculation clean. Model it in U-Monkey with your real perimeter and area for the ISO 13370 figure.

Is this calculator free?

Yes — building the element, reading the U-value, the compliance targets (including the Future Homes Standard) and the condensation-risk screening check are all free in your browser, and the Building Control-ready PDF report is free too. No sign-up.

Does it follow the official calculation method?

Yes — the combined method of BS EN ISO 6946:2017 with BR 443 conventions, including timber bridging and air-gap corrections, ISO 13370 for ground and suspended floors, and ISO 13788 for the condensation screening check.

Other common build-ups

Need the wider compliance picture? U-values feed straight into SAP calculations — or let our New Build Compliance Pack handle the lot. Background reading: what U-values actually are.

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