UK Building Regs Part L: Fassaden-Dämmung 2026 (GB)

Approved Document L — Conservation of Fuel and Power — forms part of the Building Regulations 2010 (England) and sets legally binding minimum energy performance standards for the fabric of buildings. The 2021 edition, which came into force on 15 June 2022 for new dwellings (Volume 1) and existing buildings (Volume 2), significantly tightened wall U-value requirements as part of the UK's pathway to the Future Homes Standard. For EIFS (WDVS), external render and painting contractors, compliance with Part L is a legal obligation whenever their work forms part of a notifiable building project.

For new dwellings, the maximum permitted U-value for external walls is 0.18 W/m²K, down from the previous 0.30 W/m²K. For existing buildings undergoing renovation where more than 50% of a thermal element's surface is being renovated, the threshold U-value is 0.30 W/m²K — meaning that if the existing wall is below this standard, it must be upgraded. All contractors carrying out or overseeing such work are responsible for ensuring the specification meets or exceeds these standards. Building owners and principal contractors bear primary legal responsibility, but sub-contractors can face liability if they knowingly install non-compliant systems.

In practical terms, achieving 0.18 W/m²K on a typical masonry wall generally requires between 100 mm and 150 mm of EPS or mineral wool insulation under the render finish, depending on the base wall construction. EIFS/WDVS systems must use components with third-party certification (e.g. British Board of Agrément (BBA) certificate or European Technical Assessment (ETA)), and the overall system — including fixings, insulation board, render and finish coat — must be assessed as a complete system. Painters and applicators must follow the system manufacturer's specification precisely to maintain certification validity.

Building work that is notifiable under the Building Regulations must be approved either by the Local Authority Building Control (LABC) or by an Approved Inspector (private sector). For new homes, NHBC acts as both warranty provider and approved inspector for the majority of UK housebuilders and checks compliance at key stages. Contractors should submit a building notice or full plans application before work begins, maintain site records of insulation product certificates and U-value calculations, and ensure a final completion certificate is issued. In Scotland and Wales, equivalent but separate regulations (Section 6 of Scottish Building Standards and Welsh Approved Document L respectively) apply with similar but not identical requirements.

Note: This article does not constitute legal or financial advice. Please consult a qualified professional for advice specific to your circumstances.

Umsetzungs-Checkliste

1. Check whether planned wall work is 'notifiable' under Building Regulations 2010
2. Confirm target U-value: ≤0.18 W/m²K (new build) or ≤0.30 W/m²K (existing renovation)
3. Select a BBA- or ETA-certified EIFS/WDVS system appropriate for the substrate
4. Commission a U-value calculation (BS EN ISO 6946) from a qualified assessor
5. Submit a Building Notice or Full Plans application to LABC or Approved Inspector (e.g. NHBC)
6. Install insulation and render strictly in accordance with the system manufacturer's specification
7. Retain all product certificates, delivery notes and installation records on site
8. Obtain a Completion Certificate from LABC/NHBC upon satisfactory inspection