On the work site

chaux aérienne pour une décoration créative

Creative decoration with air lime

Air lime has long been used for decorative purposes, trompe l’oeil architectural features, ersatz materials, etc. Here, Christine Biard-Feltre applies traditional techniques to deliver an original and high-impact contemporary creation. Be inspired (by materials)!

Interview with Christine Biard-Feltre on 8 May 2019: Weber Tradical®

Context: We met up with Christine in a two-storey 1930s house in the Haut-Doubs department in France. The interview took place in a cosy ground-floor room.


Weber: What was your source of inspiration?

Christine Biard-Feltre: The project owner wanted to base this creation on a painting by a local artist, which was to be adapted to the area to be decorated.


Weber: Could you explain the concept behind this air lime decoration?

CBF: It’s a decoration based on the idea of layers, using the wooden panelling as a visual starting point. The colour of the panelling is dark, and is also used on the window and door frames, making the openings part of the creation too.


Weber: Would it be right to say that each individual layer seems quite complex?

CBF: Yes, in the sense that each one is made up of several hues. But on another level, there’s also an interplay between transparency and opacity. This gives an additional opaque-to-transparent effect, running from the first stratum just above the wooden panelling to the lightest part of the decoration at the top.

At the bottom, the waxed stucco gives a bold colour, whereas towards the top, a lighter effect is produced using limewash, patina, glazes, etc.


‘This decoration showcases all the lime-based techniques’


Weber: What was your method for the actual decoration work?

CBF: I worked wall by wall. First I prepared all the colours, with enough of each for the whole surface area to be decorated. This was to ensure overall coherence for each phase.

There were at least ten different colours over the initial primer coat, not to mention the altering effects of materials and density.

And for the third and lightest surface area, from 1.5 metres high, I also created an arrangement of very blurred layers, ranging from brown to beige and textured using sands. I then covered the whole work with a patina, varying slightly in transparency, to allow alternating hues of colour to come through.

After that, I applied a polychrome separation between the three decorative areas to highlight the character of each one


Weber: How can you keep preparations simple for this type of creation?

CBF: All the colours were made using air lime (Tradical® H98) as a base product to which I then added sands, pigments, casein, etc. This provided me with a single medium to ensure consistency in terms of materials and in terms of drying time (overnight drying between each phase). In the end, despite the aesthetic scope and thus the need for several applications, the decor work only took five days. The whole job, including painting the woodwork, took ten days.

chaux aérienne pour enduit, badigeon et patine

air lime for rendering, limewash and patina

Weber: The final effect is that the walls take on the look of a painting!

CBF: Yes, it provides all the decor you need. We are in the lounge and very few additional furnishings are necessary, just a screen and two or three objets d’art. The overall composition is perfect for the project owner who, as an organ and harpsichord maker, embraces art and creation every day.


Note: Christine Biard-Feltre has a diploma from the Ecole d’Avignon and is officially qualified as a Peintre en Décor du Patrimoine (heritage painter-decorator). The nine-month course she took enabled her to gain the technical and artistic knowledge required for restoration work. The aim of the course is to familiarize students with traditional materials and their uses. Equipped with this knowledge, Christine Biard-Feltre carries out restoration and creative work on all types of substrate and adapts her skills to all pictorial styles.


Air lime project profile:


Air lime product solution

Limewash and lime patina: Tradical® H 98, which is a hydrated air lime in powder form graded as CL 90 S as per European building lime standard NF EN 459

Contact us for more information


chaux aérienne pour une décoration exclusive

exclusive decoration with air lime

Weber Tradical, your expert in hempcrete and air lime

préfabrication béton de chanvre pour une base logistique

Short prefabrication lead times with hempcrete

Two major challenges for building a local authority technical services building: a fast turnaround time and no cost overruns.

Tradical® Hempcrete is now being used for local authority technical services buildings too! The Taffeneaux logistics base, intended for servicing and repairing household waste collection vehicles, is proof of the progress this highly versatile material is making.

Weber’s Tradical® Hempcrete was chosen because it met the two requirements: an extremely fast turnaround time and a tight budget. Concerned to keep the impact of this work to a minimum and wanting an operational building in record time, the contracting authority, Sables d’Olonne district council, called on CAN-ia.

From study to delivery in twelve months

The whole project, from the initial study and project planning to choosing the architects and builders, finalising the building processes, constructing the building and handing over the keys, took twelve months. What a challenge, with an unusually tight building schedule to boot!

The key to success was prefabricating all the timber and Tradical® Hempcrete panels off-site.

An extremely tight schedule was drawn up, streamlining all the building stages and limiting their cost to save time. This led to innovative designs and building methods.

Two inverted sloping roofs for a black and white architectural project

Tradical® Hempcrete fitted right in, naturally. Today this material is increasingly popular for publicly contracted projects.

In the case at hand, it is most probably the first ever technical services building (where waste management is concerned at any rate) to have been built using this material.

The contracting authority wanted a speedy turnaround time, yet also a ‘quality building’, a double requirement met by Tradical® Hempcrete.

The project submitted by CAN-ia offered a beautiful, functional and cost-effective design, and chose a green approach, proposing to use the bio-based material Tradical® Hempcrete, which also meant the project could be finished even faster than a standard building project.

The hempcrete plan

The plan was to have a parking area equipped with a wash station, a fuel station and a workshop for servicing and repairing waste collection trucks, but also offices and changing rooms for employees.

This double requirement inspired CAN-ia to propose a design with two separate buildings, playing with the volumes and visual effects.

Two inverted sloping roofs would enable the office building to counterbalance the much bigger workshop building.

A bio-climatic approach

The office building faces south to make the most of the sun in winter (in summer, the regulating properties of hempcrete means there’s no need for air conditioning), and the workshop faces north. This was a conscious decision for the workshop, which requires non-dazzling natural light.

A large covered walkway links the two buildings, providing users with protection from the sun and rain. Its slanted posts are inspired by rows of trees in a forest.

Timber and hempcrete – the perfect match

The two materials work really well together here. The glue-laminated timber framework of the building was made by local company LCA, who also made the prefabricated panels for the frame structure.

The advantage of timber framing for the builder is its flexibility, which allows for all kinds of shapes. The walls of the envelope for the office building were made out of hempcrete (with a render finish).

The glue-laminated timber framework carries the loads and a standard assembly method was used (beams – sills).


→ View the building work project brief


PROJECT PROFILE – The Taffeneaux logistics base

Project actors

  • Project owner: Sables d’Olonne district council
  • Main contractor:   CAN-ia – Hangar 20, 20 Quai des Antilles, 44200 Nantes, France. can-ia.fr.
  • LCA – Les Charpentiers de l’Atlantique: Timber framework and Tradical® Hempcrete panels
  • Entreprise Fernandez: Tradical® Hempcrete casting in LCA’s workshop

Contact us for more information 


Case study produced by Sandrine Wiart, Weber Tradical® Press Officer. Tel: +33 (0)134 947 733

Weber Tradical, your expert in hempcrete for houses, air lime, hemp lime render and more

extension béton de chanvre st malo

Craft and design for a hempcrete extension

With hempcrete you can build and restore. Here, the project was an extension, a meeting of old and new. The idea was to create an additional room using state-of-the-art eco-friendly materials and an eco-friendly approach.

Entreprise Durand Bâtiment 1/3
Interview with Fabien Pautrel on 17 May 2018: Weber Tradical®


Weber: The timber framework is the first thing that strikes you!

Fabien Pautrel: Yes, on this project, the framework stands out with its unusual thick timber sections playfully arranged in a contrasting chevron and cross design between closely spaced load-bearing posts.


Weber: What’s the configuration for this extension?

FP: It covers a floor area of 30 to 40 m², with a gable wall on one side belonging to a house made of granite near St Malo. Hempcrete was used for the floor slab.

The plinth is made of local stone retrieved from a demolition. It was laid using Tradical® formulated lime and the interior was lined with pumice stone masonry. The whole plinth was topped with a levelling course on which the timber structure rests.


Weber: And what about the insulation?

FP: The owner assigned the design to a main contractor specialised in thermally insulating eco-friendly materials. So naturally, Tradical® hempcrete became a part of the project. We manually cast the hempcrete between shuttering panels, wall by wall. We cast in 50-cm-high layers, from the ground floor to under the eaves.

The framework design is visible from the inside. The hempcrete was flush to begin with, but a 10 mm layer was scraped off after removal of the shuttering formwork while the hempcrete was still fresh. A lime and sand finish was then applied, flush with the timber work.

Woodwool was placed over the wood and hempcrete wall on the outside, and was cladded with timber.


Weber: How did you handle the conduit and pipework?

FP: The conduits run through the draining layer and are embedded in the hempcrete.


Weber: Can this extension be rated as high-end?

FP: No, in terms of size, but yes when it comes to the technical choices made. One thing’s for sure, all the different materials used for this project made progress more complicated, with extensive phasing.

It was a project spearheaded by high-quality materials and expert knowledge. The timber sections were fastened together using traditional mortise and tenon joints, and the pegs were made of wood too.


Project profile

  • Project owner: Private individual
  • Location: St Malo
  • General contractor: Durand Bâtiment – La Ville Joie, 35540 Le Tronchet, France | durand-batiment.frcontact@durand-batiment.fr
  • Products: Tradical® Hempcrete
  • Wall application: Tradical®PF 70 + Chanvribat®.
    Tradical® PF 70 is a building lime complying with standard NF EN 459


Contact us for more information

Build with hempcrete with Weber Tradical, your expert in hempcrete, hemp lime render and more

restauration d'un monument historique Luxembourg

Restoration of an iconic historic building in Luxembourg

Hempcrete was placed at the heart of major restoration work on an iconic chateau in Luxembourg. This bio-based material has proved its worth as an ideal solution to meet all the requirements for renovating a historic building.


Construction of one of the most important chateau of the Grand Duchy of Luxembourg.


Renovation and insulation of the chateau with Tradical® Hempcrete


In the period intervening these two dates, the Grand-Château d’Ansembourg left lasting impressions, with its extensions, its economic role, its ever-flourishing gardens and park, its different owners and its important place in Luxembourg’s heritage.

Surrounded by world-famous, picturesque botanical gardens, where the delicate and fragrant Jardins d’Ansembourg rose was recently unveiled, the Château d’Ansembourg is experiencing a rebirth thanks to the expert advice of the Service des Sites et Monuments Nationaux or SSMN (Luxembourg’s department for national heritage).

The renovation work made it crystal clear that using a natural, bio-based material, such as Tradical® Hempcrete, is the right and best solution for (insulating and) renovating historic buildings.

The work was also a perfect example of artisan builders working intelligently and communicatively together to organise and complete a large-scale project.

A whole range of tough constraints shaped this renovation and led to specific technical choices and ingenious solutions.


From quick renovation to large-scale project

To begin with, the project owner wanted a simple renovation of the first floor. However, preliminary surveys and inspections revealed that there were significant structural problems requiring a more general overhaul: cracks, sagging floors and stairs, etc.


A further issue – dry rot

Dry rot was identified in just a few places at first, but unfortunately, it soon became clear that it was more widespread (affecting 700 m²). The initial renovation project had to be completely revised to incorporate an approach closer to archaeology than renovation.

The renovation suddenly went from work on a just few dozen square metres to having to perform work on all the floors of the central building. Work was therefore undertaken on the structure and to treat the dry rot.


Finding the right solution

Now a large-scale project, the renovation of this part of the building brought several building specialists together to find a solution to meet all the constraints involved:

  • Ensuring that the layout and ornamental features of the interiors were kept – sculptures, beading, overhangs, intersecting ribs, etc.
  • Preventing the return of dry rot by creating the conditions for maintaining constant temperatures and moisture levels.
  • Ensuring walls can breathe to guarantee longevity.
  • Providing high-performance insulation.
  • Recreating the natural historic look and feel (while also integrating any necessary modern elements).


An on-site and decisive test

In 2016, the hempcrete underwent a full-scale test on site in the annex off the Salon Bleu (blue room) on the first floor, a room measuring about 4 by 4 metres.

44 m² of surface area were lined with hempcrete cast on an embedded metal framework. The results confirmed the vapour permeability and acoustic performance of this bio-based material, and proved that this insulating lining could be used without compromising the architecture and the different decorative or ornamental elements.


Hempcrete insulation – a compelling approach

The idea of using hempcrete was quickly adopted, as the material provided:

  • The right humidity control characteristics to enable the façade to breathe.
  • Consistent material characteristics to prevent dry rot from reappearing. Dry rot comes from the stonework and spreads if certain humidity and temperature conditions come together. The fact that hempcrete provides a constant surface temperature for interior walls avoids such conditions arising.
  • An indoor temperature of 20°C, as requested by the project owner.


Restoration choices governed by architecture and heritage

An inverted metal framework

With cellulose-hungry dry rot in mind, metal had to be used for the secondary framework. Profiles were positioned vertically at 40 cm intervals and a few centimetres away from the substrate.

For a perfect infill and an even coating of profiles, and to meet, for example, the specific thickness required for the correct distance between the flat surface featuring the decorative friezes of the vaults and the flat surface of finished insulated walls (recommended by the SSMN), Weber Tradical®’s Technical Manager, Yannic Santandreu, proposed the ingenious solution of using U-shaped profiles.

Tracks (48 mm) were positioned with the concave part of the profile facing outwards. This solution ensured that the profiles were coated with a sufficient thickness of hempcrete to support the expansion and contraction effects inherent to all materials, and avoid any deterioration through fissuring.

The hempcrete was made in a concrete mixer and poured into the gap between the OSB shuttering panels and the walls, in compliance with the French professional rules for hempcrete. Thanks to this innovative solution, the framework was firmly coated with a thickness of between 7 and 10 cm.


Reversible insulation work – a must for renovating historic buildings 

One of the main concerns of the project owner and the SSMN was that the work undertaken should not damage the original building. The insulation had to be removable should the need arise in the future. Hempcrete supported by a metal framework that is separate from the substrate can be easily removed if necessary.


Maintaining breathability with air lime finishes

An air lime finish was applied to the hempcrete as a thin coat of render – Tradical® Décor –  whose vapour permeability is in perfect harmony with the moisture transfers inherent to this bio-based insulation. The thin lime render was also used on the mineral-based wall substrates adjacent to the insulated walls. The advantage of this render is that any work delivered is texturally and visually harmonious, regardless of the type of substrate to be finished.


A constructive meeting of artisan builders – or the small business’s guide to completing large-scale projects

Atelier Saint-Fiacre France (stone cutter), Entreprise Hennen, Société Millereaux and Atelier Montomble, all won over by hempcrete and trained by Weber in the use of Tradical® Hempcrete, took a methodical approach. They pooled their efforts, shared their experiences and knowledge, tightly scheduled the different work stages and optimised costs. A work and primary material delivery schedule was set out over period of about ten months, at a rate of one week of work per month.


Project profile for the restoration of a historic building

  • Work site: Grand-Château d’Ansembourg
  • Location: Ansembourg, Grand-Duchy of Luxembourg
  • Purpose of the building: Tourism, seminars
  • Characteristics of the building: Historic building (dating from 1640)
  • Project owner: Private project owner
  • Main contractor: Agence N. Madoki
  • Restoration supervised by: Service des Sites et Monuments Nationaux
  • Builders & artisans using hempcrete: Atelier Saint-Fiacre France (stone cutter) / Entreprise Hennen / Société Millereaux / Atelier Montomble
  • Expected delivery: 2019
  • Surface area concerned: 1,500 m²
  • Product volume: 130 m of hempcrete



  • Tradical® Hempcrete bio-based insulation: Tradical®PF 70 lime + Chanvribat® hurds
  • Thin air lime-based interior finishing render: Tradical®Décor


Tradical® Hempcrete quality hallmarks:

  • Certified aggregate
  • Made in France
  • Compliant with French Professional Rules


For further information:


Note 1: extract from the press kit produced by Sandrine Wiart, Weber press officer, in June 2018. Document title: AT THE HEART OF MAJOR RESTORATION WORK ON AN ICONIC CHATEAU IN LUXEMBOURG: HEMPCRETE. The kit was finalised after a press visit to the site on 27 June 2018.

Note 2: Photo credits – ©Weber Tradical®

Insulating attic spaces to keep your house inherently cool

Roofs are often the cause of reduced thermal efficiency in summer and winter. Insulating attic spaces is first thing to do when you renovate. Your energy bills plummet immediately when you remove the need for air conditioning in summer.

We discussed the subject with Dominique Burg, a specialist in eco-friendly materials for renovations working from an office in the Quercy area in south-west France. The environmentally preserved Quercy area has naturally led him to opt for hempcrete solutions, to stay in keeping with his clients’ preferences.

He also works on new builds. The house he is currently building is ideal for testing different casting methods to increase his efficiency on projects involving this material in the future.

  • 1/2 Entreprise SEE Burg
  • Interview with Dominique Burg on 14 May 2018: Weber Tradical®


Weber: Why is a well-insulated attic so important for you?

Dominique Burg: We get a lot of sunshine in our region, with average temperatures of around 30°C in summer. To keep indoor spaces cool, I’m a strong advocate of installing insulation that’s effective for that period of the year and can counter overheating.

Having an attic you can use as a pleasant living space is a real plus for house owners. My approach is therefore to offer an environmentally friendly solution that cuts back on energy costs.

Hempcrete has proved to be the ideal solution for insulating attic spaces under these conditions.


Weber: Have you ever tried other solutions? On earlier projects for example?

DB: Yes, I have actually tried using lightweight insulating materials such as cellulose, wool and so on, but they don’t work in summer. If you don’t have air conditioning, converted attic spaces just can’t be used. And let’s not forget that air conditioning is not only high-maintenance but also uses a lot of electricity.

It’s absurd to have an energy bill that’s larger in summer than in winter. The real issue is how to keep the temperature down indoors. What people want in a home is a good living atmosphere.

Hempcrete is as effective in summer as in winter.


Weber: How are you organised in terms of casting?

DB: We made the most of this building project to try out the different ways of casting hempcrete, the main aim being to gain in efficiency on projects in general. We compared the times for casting hempcrete using a mechanical projection solution and a solution involving a mobile concrete mixing station with a telescopic chute.


Weber: What were the main differences between these two processes?

DB: We had to install the equipment for mechanical projection quite high up to reduce the length of the pipe and ensure it was level as much as possible. This was to obtain the maximum possible output of 3 m3 per hour.

As for the mobile concrete mixing station, the procedure was completely different as we were mixing large quantities of hempcrete – up to 40 m3 per hour. The Tradical® lime + Chanvribat ® hemp + water mix was very high quality. The real output was actually dictated by the speed at which the hempcrete could be cast for the roof.


Weber: What did you do in terms of lost formwork?

DB: Here again I made the most of it to try out two very different solutions. In the first case, the lost formwork consisted of storey-height panels. The advantage is that you can apply the finish directly on these substrates. In the second case, I used battens made of poplar. This is a stronger substrate and also has the benefit that you can dissociate the finish from the lost formwork and thus the hempcrete.


Weber: What else is on the programme for the rest of the house?

DB: We’re going to compare the same two casting methods for creating 120 m² of insulated walls and insulating Tradical® hempcrete screeds. We’re also going to apply a lime and sand render to finish the exterior of the house. The interior is going to be decorated using a mix of moisture and heat-regulating hemp renders and lime plus mud renders. Heating will be provided by a masonry stove.

The house will soon be ready to show off its energy efficiency over the summer and throughout the following seasons!


Project profile 

  • Project owner and main contractor: Dominique Burg
  • Town: Saillagol, France
  • Surface area: 160 m2
  • Altitude: 300 m
  • Climate zone: H2c
  • Insulation: The roof, wall and screed are cast with Tradical®Hempcrete
    • Using Tradical®Thermo + Chanvribat®
      • An approved material blend that complies with the performance requirements laid down by French professional rules.
      • Certified fire-resistance rating
      • Certified lambda value of 0.056 W/m.k for attic insulation and 0.076 W/m.k for wall insulation.


For further information

Case study 06 – An energy-efficient house in the Doubs

Only 1,500 kg of wood pellets required for heating

In our ‘Feedback on heating costs’ series for hempcrete houses, this is the sixth conclusive case study.

In Roche-Les-Blamonts, where temperature and weather can fluctuate considerably within the same day, there is nothing better than Tradical® Hempcrete to counterbalance these variations and ensure that indoor temperatures remain stable, leading to greatly reduced energy consumption whatever the season:

The profile of this low-energy house

  • Surface area: 100 m²
  • Altitude: 420 m
  • Climate zone: H1c


Construction system

  • The building rests on a 40/60 granular fill which contains all the networks. A drained hardcore layer was placed on top of this.
  • The main house, adjoining garage and extension are all built using Tradical® Hempcrete.
  • This eco-friendly building has benefited from an innovative timber framework made of vertical wall panels, making it easier to coat the structure with the lime-hemp composite.
  • This composite material was projected on the exterior, over lost formwork. Timber cladding was then added to finish the façades.
  • A hot water tank was installed for DHW
  • The house is heated by a wood pellet stove


Bio-based hempcrete insulation in five areas


  • Tradical® Hempcrete insulating walls, where R = 4.7 m²K/W for a thickness of 40 cm
  • A Tradical® Hempcrete insulating roof, where R = 5 m²K/W for a thickness of 30 cm
  • A Tradical® Hempcrete insulating screed, where R = 2.1 m²K/W for a thickness of 20 cm


  • Tradical® Hempcrete insulating layer in the unused attic space, where R = 2.1 m²K/W for a thickness of 20 cm


  • Tradical® Hempcrete insulating walls, where R = 2.4 m²K/W for a thickness of 20 cm


A very low environmental impact

Bilan CO2Label Bâtiment BiosourcéVolume Béton Chanvre Tradical®
19 t de CO2 captéEligible niveau 368 m3


Summer comfort with no air conditioning required

Example for July 2016

  • Outdoors: an average temperature of 15°C at night and 30°C in the day
  • Indoors: a daytime average temperature of 25-26°C with high outdoor temperatures


Thermal comfort in winter

  • Outdoors: an average temperature of 0°C at night and 9°C in the day
  • Indoors: a daytime average temperature of 22-23°C


Contact us!


In addition to this article, why not also read the five other case studies published in early 2017