As the demand for healthier, more sustainable building materials continues to grow, hemp lime plasters are an increasingly attractive alternative to traditional sand–lime mixes. TopLime™ Hemp and BaseLime™ Hemp Plasters offer a combination of performance, durability and environmental benefit that sets them apart backed up not only by practical site experience but by technical performance data.
In this post, we explore the key reasons why these hemp plasters are gaining ground across renovation and new‑build projects alike.
Strength Through Fibre: Improved Flexural and Compressive Behaviour
One of the most significant advantages of TopLime™ Hemp and BaseLime™ Hemp Plasters is their fibrous structure. The hemp fibres provide excellent flexural strength compared with typical sand–lime plasters. According to the technical data:
· Flexural strength
- TopLime Fine Hemp: 2.2 N/mm²
- BaseLime Medium Hemp: 1.28 N/mm²
· Compressive strength
- TopLime: 2.8 N/mm²
- BaseLime: 2.5 N/mm²
For reference a typical non hydraulic sand lime plaster has flexural and compressive strength less than 1 N/mm²
This enhanced flexural performance gives the finished surface far greater resistance to cracking and movement, delivering a tougher, longer‑lasting result. As well as impact resistance in the day to day usage of a room.
Lightweight with Added Insulation Value
Hemp plasters are noticeably lighter than sand–lime mixes and provide slight thermal benefits. The thermal conductivity values highlight this:
· Thermal Conductivity (λ):
- TopLime: 0.3365 W/mK
- BaseLime: 0.2658 W/mK
For comparison again a typical value for standard mineral based plaster is 0.43 W/mK.
This makes the materials easier to work with, reduces load on substrates, and adds modest insulation—particularly useful on retrofit projects where every gain counts.
Thick Coat Application for Efficient Build‑Up
BaseLime™ Hemp can be applied in coats up to 25 mm, and TopLime™ Hemp up to 15 mm, making them ideal for dubbing out uneven walls, levelling substrates, and speeding up the overall build‑up process. This thickness capability gives installers far more flexibility compared with sand–lime plasters that require thinner, more carefully managed coats.
Reduced Tending and Lower Shrinkage Risk
A common challenge with traditional lime plasters is shrinkage cracking, especially in warm or dry conditions where moisture is lost too quickly. Hemp fibres naturally retain moisture for longer, reducing shrinkage and typically removing the need for spraying between coats. This makes the system both robust and straightforward to manage on site.
A More Sustainable, Low‑Carbon Plaster
Hemp‑lime plasters have clear environmental advantages:
- They replace quarried sand with plant‑based fibre.
- The product is entirely British‑made, keeping transport footprint low.
- Hemp cultivation sequesters carbon during growth.
For builders and clients prioritising sustainability, this makes TopLime™ Hemp and BaseLime™ Hemp strong alternatives to standard mineral plasters.
Vapour Permeability and Acoustic Improvement
Vapour permeability is one of the major strengths of lime‑based materials, and hemp enhances this even further.
· Vapour Permeability:
- TopLime: 8.75×10⁻¹¹ kg/(m·s·Pa)
- BaseLime: 9.1×10⁻¹¹ kg/(m·s·Pa)
As a comparison non hydraulic sand lime plaster falls in the range of (4–7) × 10⁻¹¹ kg/(m·s·Pa)
These values indicate excellent moisture movement, allowing walls to regulate humidity and remain dry, healthy and mould‑resistant. The fibrous texture also provides worthwhile acoustic damping, improving interior comfort.
High‑Quality Finishes in Just Two Coats
TopLime™ Hemp can be finished in two different ways:
- Used alone for a natural, slightly textured hemp finish.
- Mixed 50:50 with a topcoat plaster for a smooth, refined surface.
- Alternatively, it can accept a traditional fine topcoat.
Because the system requires only two coats, it significantly cuts both time and cost.
TopLime Hemp left. TopLime Hemp Blend (50/50 with Toplime Internal) right.
Real Material Savings
Based on a 100 m² application, the two‑coat hemp system can reduce material consumption by up to 40%, with further savings in delivery charges and labour time. For contractors looking for efficiency without compromising quality, this is a clear advantage.
Suitable for a Range of Substrates
TopLime™ Hemp adheres excellently to a variety of internal surfaces, including:
- Woodfibre insulation boards
- Wood Wool boards
- Traditional masonry
This makes it suitable for retrofits, heritage work and natural‑build projects as well as modern construction. Adhesion to boards of TopLime™ Hemp has a tested value of 0.04 MPa – this is typical for non-hydraulic lime plaster.
Conclusion
TopLime™ Hemp and BaseLime™ Hemp Plasters combine performance, sustainability and cost‑efficiency in a way that traditional sand–lime plasters cannot match. Their strength, breathability, reduced shrinkage, ease of application and environmental credentials make them a compelling choice for builders, designers and homeowners aiming for high‑quality, low‑impact construction.
