Hempcrete in the UK: Benefits, Limits and Suppliers

What hempcrete is

Hempcrete is hemp shiv, the woody core of the hemp stalk, mixed with a lime-based binder and water. It is also called hemp-lime. It is cast between shuttering on site, sprayed, or supplied as pre-cast blocks and panels.

It does not replace concrete. It is a low-density wall infill and insulation, also used in floors, that adds some thermal mass. The shiv is a co-product of hemp fibre processing.

Benefits of hempcrete, with the numbers

Hempcrete’s measured benefits are insulation, vapour permeability, moisture buffering, fire performance and stored carbon. Every figure below is tied to a named source and a specific mix or product. Treat them as ranges, because density drives most of the properties.

Insulation and thermal mass

Hempcrete insulates moderately well and stores heat. Abdellatef and colleagues measured 0.087 to 0.10 W/m·K on mixes averaging 323 kg/m³, and cite earlier studies at 0.06 to 0.11 W/m·K for densities of 200 to 400 kg/m³.

Denser mixes conduct more heat. Collet and Prétot found that raising density by about two-thirds raised thermal conductivity by about 54%. Moisture mattered less: going from dry to 90% relative humidity raised it by less than 15-20%.

For a whole wall, IsoHemp gives a thermal resistance of up to 5.37 m²·K/W for its 36 cm block. East Yorkshire Hemp states a U-value of 0.2 W/m²·K for a 300 mm hempcrete wall. Both are suppliers’ own figures.

Vapour permeability and moisture

Hempcrete lets water vapour pass and evens out indoor humidity. Manufacturer data puts the vapour diffusion resistance factor at 4.84 for Tradical Hemcrete and 2.8 for IsoHemp blocks. A lower number means more vapour-open.

Abdellatef et al. measured an average moisture buffer value of 2.78 g/m²·%RH, which the authors describe as excellent moisture buffering.

Fire

Tested hempcrete assemblies resist fire for an hour or more. The Limecrete Company’s factsheet reproduces Lime Technology data giving Tradical Hemcrete a 1 hour rating to BS EN 1365-1:1999. IsoHemp states class B-s1,d0 for reaction to fire, and fire resistance from 45 minutes for a 7.5 cm block to 240 minutes for 30 cm and above.

A fire rating belongs to the tested build-up, including its thickness and finishes. It does not transfer to a different wall.

Carbon

Hempcrete can store more carbon than it takes to make, within the limits of each study. Ip and Miller (2012) modelled a UK hemp-lime wall, 1 m² in area and 300 mm thick with a timber frame. They found it could sequester 82.7 kg of CO2, with a net life cycle reduction of 36.08 kg CO2e over 100 years.

Suppliers quote per-volume figures: 130 kg CO2 per m³ in the Tradical Hemcrete data, and 60-165 kg per m³ from UK Hempcrete, depending on materials and application. The result depends heavily on the binder and on what is counted.

Limits of hempcrete

Hempcrete’s main limits are strength, drying time and cost.

• It is not structural. UK Hempcrete says hempcrete is not load-bearing and is self-supporting once set. Measured compressive strength in Abdellatef et al. was 0.09 to 0.57 MPa. Pochwała and colleagues note its very poor load-bearing strength and say it needs a separate load-bearing structure, most often softwood timber.
• Cast walls need time to dry. UK Hempcrete says drying time for cast-in-situ hempcrete varies with the weather and can affect the programme. The Limecrete Company’s factsheet says shuttering can be struck the next day, lime render follows after 4 weeks in fair weather, and the top coat 2 weeks after that.
• Walls are thick. The supplier U-values above are for walls of 300 mm and more.
• Cost. The Hemp Block Company publishes block prices, dated 14 February 2025 and excluding VAT and delivery: £43.13 per m² for 120 mm blocks, £94.17 per m² for 300 mm and £125.56 per m² for 400 mm. These are materials only. No sourced figure for installed cost was found for this page.
• Results vary by mix. The published ranges above are wide. Use the data sheet for the exact product you buy.

UK Building Regulations

Hempcrete has no special status in the Building Regulations. It has to meet the same functional requirements as any other wall.

• Materials and workmanship. Approved Document 7 covers regulation 7 in England: building work must use proper materials and be carried out in a workmanlike manner.
• Energy. Approved Document L, Volume 1 (2021 edition with 2023 amendments, for use in England) sets a limiting U-value of 0.26 W/(m²·K) for walls in new dwellings. The document adds that some elements will need to be significantly better than the limiting standards for the dwelling to hit its overall targets.
• Newer edition. The GOV.UK page for Approved Document L also links 2026 editions for buildings subject to the 2026 standards. Confirm with building control which edition applies to your project.

These documents apply to England. This is general information as of October 2026, not regulatory advice.

UK hempcrete suppliers and builders

The nine companies below had live websites on 9 October 2026. Descriptions use only what each company states on its own site. The order is not a ranking.

For US firms, see US hempcrete companies.

Next step

Ask two or three of the suppliers above for the technical data sheet of the exact product, then take the wall build-up to your designer and building control before you order.