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Hempcrete building regulations and planning permission

6 min read

A practical guide to getting hempcrete approved — building regulations in the UK and US, planning permission, and how to work with building control.

Hempcrete is not an experimental material; it's been used in construction for decades, and approved pathways exist in both the UK and US. That said, it sits outside the mainstream of conventional building materials, which means navigating building regulations requires some preparation. This guide covers what you need to know before you start.

The regulatory landscape

Building regulations exist to ensure that structures are safe, energy-efficient, and fit for purpose. They don't, in most jurisdictions, mandate which specific materials you must use, only that the finished building meets defined performance standards. This is important for hempcrete: the question building control will ask is not "is this hempcrete?" but "does this wall meet the required thermal, structural, and fire performance?"

This distinction matters. A well-specified hempcrete wall can meet or exceed the performance requirements of conventional construction. The challenge is demonstrating that it does so, and that requires documentation, specification, and in some cases, third-party testing data.

UK building regulations

In the UK, building regulations are administered by Local Authority Building Control (LABC) or approved inspectors. Hempcrete falls under Part L (energy efficiency), Part A (structural safety), and Part B (fire safety) of the Building Regulations for England and Wales, with equivalent provisions in Scotland and Northern Ireland.

Approved pathways

Hempcrete doesn't appear in the standard Approved Documents, which means it can't be specified by simply referencing a document number. Instead, approval is typically sought through one of two routes:

The Tradical® Hemcrete® system, manufactured by Lhoist UK: this is currently the only hempcrete walling system with LABC pre-approval and an available LABC warranty. Specifying this system gives the most straightforward route through building control, particularly for projects where the contractor or client wants certainty of approval before work begins.

Individual project approval: projects using other binders or non-standard specifications can seek building control approval on a project-by-project basis. This requires submitting technical documentation including thermal performance calculations, structural details, and fire test data. Many projects have been approved through this route, but it requires more preparation and early engagement with building control.

Practical advice for UK projects

  • Engage building control early. Do not wait until you have planning permission to speak to your building control officer. An early conversation lets you understand what documentation they'll require and avoids surprises late in the project.
  • Use a specialist consultant. Companies specialising in hempcrete construction can provide the technical documentation and calculations that building control requires. The cost of this is modest relative to the overall build cost.
  • Prepare a material specification. A clear document setting out the binder type, mix design, wall thickness, and expected thermal performance (U-value) is the foundation of any building control submission for hempcrete.
  • Heritage and retrofit projects often have an easier path through building control, as hempcrete is well suited to use in older buildings and its breathable properties align with conservation objectives.

US building regulations

In the United States, building codes vary significantly by state and municipality. The model code used by most states is the International Residential Code (IRC), published by the International Code Council (ICC).

The 2024 IRC update

A significant milestone for hempcrete in the US came when the ICC added hemp-lime construction to the 2024 edition of the International Residential Code. This introduced Appendix BL, Hemp-Lime Construction, which provides standardised guidance for how hempcrete can be used in residential buildings. Under this appendix, hemp-lime is formally recognised as a non-structural insulating infill material used alongside a structural frame.

This is a major step forward. Previously, every hempcrete project in the US required approval as an alternative material under Section R104.11 of the IRC, a process that depended heavily on the individual building official's familiarity with the material.

State and local adoption

The 2024 IRC doesn't automatically apply everywhere. Individual states, counties, and cities must formally adopt each new code edition before it becomes locally enforceable, and that process can take several years. Many jurisdictions are currently using IRC 2018 or IRC 2021, which don't include the hemp-lime appendix.

However, even where the 2024 IRC hasn't yet been adopted, approval is still possible. Most building codes include provisions for alternative materials that can be approved when they demonstrate equivalent safety and performance. The existence of the 2024 IRC appendix provides useful supporting documentation for such applications, since it demonstrates that the material has been reviewed and approved at a national level.

Practical advice for US projects

  • Check your local code edition. Find out which IRC edition your jurisdiction uses and whether Appendix BL has been locally adopted.
  • Contact your building department early. As with the UK, early engagement is essential. Bring documentation including the 2024 IRC appendix, resources from the US Hemp Building Association, and your wall specification.
  • Work with an experienced contractor. Building officials are more likely to approve a hempcrete project when the contractor can demonstrate experience with the material and provide references from completed projects.
  • Allow extra time. In jurisdictions where hempcrete is new to the building department, the approval process may take longer than for conventional construction. Factor this into your project timeline.

Planning permission

Planning permission (or planning approval in the US) is a separate process from building regulations and is concerned with the visual appearance, use, and impact of a building on its surroundings, not its structural or thermal performance.

Hempcrete is unlikely to raise specific planning issues in most cases. A hempcrete building finished with lime render looks like a lime-rendered building. The planning authority is generally not concerned with what's inside the wall.

Exceptions may arise in:

  • Conservation areas and listed buildings, where the appearance and materials of the building are subject to additional scrutiny. Hempcrete is generally well received in heritage contexts, but any external finish must be approved.
  • New build in open countryside, where planning permission may be more difficult to obtain regardless of the materials used.

Summary

Getting hempcrete through building regulations is straightforward when approached correctly. The key points:

  • Performance standards apply, not material standards: hempcrete needs to meet U-value, fire, and structural requirements, not match a specific approved product list.
  • In the UK, the Tradical® Hemcrete® system offers a pre-approved route; other specifications require project-by-project approval.
  • In the US, the 2024 IRC now formally recognises hemp-lime construction under Appendix BL, a significant step forward even where it hasn't yet been locally adopted.
  • Early engagement with building control is the single most effective thing you can do to smooth the approval process.
  • Planning permission is generally unaffected by the choice of hempcrete.

Hempcrete has been approved for construction on hundreds of projects across the UK, Europe, and North America. The regulatory pathway exists; it simply requires preparation.

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