Completely free — choose Wales under the verdict and the tables switch.
Opens on a wall with the Welsh dwelling tables selected. Change the nation or building type at any time.
Dwellings — Approved Document L Volume 1 (Wales, 2022)
| Element | Table 4.1 — new and existing dwellings | Table E1 notional dwelling | Table 11.1 retained — threshold → improved |
|---|---|---|---|
| Wall (houses) | 0.18 | 0.13 | 0.70 → 0.55 cavity fill / 0.30 internal or external insulation |
| Wall (flats) | 0.21 | 0.13 | as above |
| Floor | 0.15 | 0.11 | 0.70 → 0.25 |
| Roof (all types) | 0.13 | 0.11 | 0.35 → 0.16 |
| Party wall | 0.20 | 0.0 | — |
| Windows, roof windows | 1.4 (or WER band B, existing) | 1.3 | 3.3 retained (Table 10.1) |
| Rooflights | 2.2 | 1.6 | 3.8 retained |
| Doors | 1.4 | 1.0 opaque / 1.3 glazed | 3.3 retained |
All values W/m²K. Sources: Approved Document L Volume 1: Dwellings, 2022 edition for use in Wales (in force 23 November 2022; May 2024 PDF incorporating the 31 May 2024 amendment slip) — Table 4.1 p.31, Appendix E Table E1 p.107, Table 10.1 p.70, Table 11.1 p.77. The 2026 edition takes effect 4 March 2027.
Buildings other than dwellings — Volume 2 (Wales, 2022)
| Element | New buildings | Existing buildings — new element (all other) | Essentially domestic in character | Table 4.2 retained — threshold → improved |
|---|---|---|---|---|
| Flat roof | 0.2 | 0.18 | 0.15 | 0.35 → 0.18 |
| Pitched roof, insulation at rafter | 0.2 | 0.18 | 0.15 | 0.35 → 0.18 |
| Pitched roof, insulation at ceiling | 0.2 | 0.15 | 0.15 | 0.35 → 0.16 |
| Wall | 0.26 | 0.26 | 0.21 | 0.70 → 0.55 cavity / 0.30 solid |
| Floor | 0.22 | 0.22 | 0.18 | 0.70 → 0.25 |
| Windows | 1.6 | 1.8 | 1.4 or WER B | — |
| Roof windows, curtain walling | 1.8 | 1.8 | 1.8 | — |
| Rooflights | 2.2 | 2.2 | 2.2 | — |
| Pedestrian doors | 1.8 | 1.8 | 1.8 | — |
| Vehicle access doors / high-usage entrance doors | 1.3 / 3.0 | 1.5 / 3.5 | 1.5 / 3.5 | — |
Source: Approved Document L Volume 2: Buildings other than dwellings, 2022 edition for use in Wales (takes effect 29 March 2023) — Table 4.1 pp.36–37, Table 4.2 p.40. Table 4.1 is the backstop; compliance for a new building is BER ≤ TER against the NCM notional building.
Why the nation matters
A partial-fill cavity wall of 102.5 mm brick, 50 mm cavity, 100 mm PIR, 100 mm dense block and plasterboard calculates to 0.20 W/m²K. It passes England's 0.26 dwelling backstop but fails Wales's 0.18. Take it to 150 mm of full-fill mineral wool on aircrete and it reaches 0.18 — a pass in Wales, though still above the 0.13 notional the TER assumes. The calculator will not tell you a Welsh wall passes on English numbers: choose Wales and the verdict, the hint and the PDF all switch.
How U-Monkey applies it
New build is judged against Table 4.1 with the Table E1 notional alongside; a new element in an extension or conversion against the existing-dwellings column; an existing element as built against the Table 11.1 threshold; a retained element being renovated against the Table 11.1 improved value — cavity or solid wall, floor or roof. Non-domestic work uses Volume 2's Tables 4.1 and 4.2. Windows and doors entered as specified elements use the same tables, and the free PDF states which document and table produced the verdict.
Frequently asked questions
What U-values does Part L require for a new house in Wales?
Table 4.1 of Approved Document L Volume 1 (Wales, 2022) sets the worst acceptable values: roofs 0.13, walls 0.18 for houses (0.21 for flats), floors 0.15, party walls 0.20, windows, roof windows and doors 1.4, rooflights 2.2 W/m²K. The notional dwelling used for the TER/TPER (Appendix E, Table E1) is tighter still: external walls 0.13, roofs 0.11, floors 0.11, windows 1.3.
How is Wales different from England?
Every opaque limit is tighter — roofs 0.13 against England’s 0.16, floors 0.15 against 0.18, and walls 0.18 against England’s 0.26 backstop. Wales also has one combined Table 4.1 with a new-dwellings column and an existing-dwellings column (the opaque values are the same in both), a separate wall row for flats, an explicit party-wall limit, a minimum SAP rating of 81, and no Future Homes Standard row — Wales runs its own programme.
What about extensions and renovations in Wales?
A new element in an extension or conversion meets the existing-dwellings column of Table 4.1 — the same 0.13 / 0.18 / 0.15 figures. A retained element being renovated is judged by Table 11.1: threshold values of 0.70 for walls and floors and 0.35 for roofs, improved to 0.55 (cavity wall), 0.30 (solid wall with internal or external insulation), 0.25 (floor) or 0.16 (roof). Those improved figures match England’s Table 4.3; the table number does not.
And non-domestic buildings in Wales?
Approved Document L Volume 2 (Wales, 2022) Table 4.1: new buildings roofs 0.2, walls 0.26, floors 0.22, windows 1.6, roof windows and curtain walling 1.8, rooflights 2.2, pedestrian doors 1.8. New elements in existing buildings use 0.18 / 0.26 / 0.22 (or the tighter 0.15 / 0.21 / 0.18 where the building is essentially domestic in character). Retained elements follow Table 4.2, the same thresholds and improved values as the dwellings table.
Does U-Monkey use the Welsh tables?
Yes. Choose Wales and Dwelling or Non-domestic under the verdict and the pass/fail, the hints and the PDF footer switch to the Welsh documents and name the table. The U-value calculation itself (BS EN ISO 6946, BR 443) is identical across the UK.
Elsewhere in the UK: Scotland (Section 6) · non-domestic buildings · England dwellings. Full tutorial: how to use U-Monkey.