Project Details
Date: 2019
Entreprise: AC Déco
Category: eco-renovation-houses

Project Description

Hempcrete – a perfect match

When you renovate, it is particularly important to use insulating materials that work in harmony with the materials used in the original building and that can match the longevity of old buildings. AC Déco uses all the potential of Tradical® Hempcretes to deliver renovations based on quality and comfort.

We went on a guided visit of a site in the Charente-Maritime department.
BCB Tradical® interviewed Sébastien Tinchant from AC Déco on 25 October 2019.


BCB: How did you meet your client?

Sébastien Tinchant: The building was bought by some English people who wanted to live in an eco-friendly house. They were already interested in this type of approach because of their professional work. They knew about lime and wanted to use local companies. That’s how they discovered my business and my green building experience.

I did what I always do and showed them and the main contractor round my previous work sites. That enabled me to explain the potential of hempcrete properly, in terms of thermal performance and moisture transfer, and how this material and stone work perfectly together. The heating engineer noted the characteristics provided in the Tradical® brochure to adjust the heating power of the wood chip boiler to be installed. The aim was that the client would produce his own wood chips for the boiler.


BCB: What was the configuration of the house?

ST: It was a house in Charente-Maritime with a large footprint and comprising a ground floor and two upper floors. The first floor walls were made of rubble stone and on the second floor they were made of ashlar. There were several entrances to the house via four staircases. This was very important given that part of this house was to be rented out as a gîte. The future visitors were to have their own private entrance.


BCB: What did the works programme look like?

ST: As the house was to have two uses, it had to have several bathrooms (eight in all). The project owner wanted to use hempcrete for insulating the walls and the ground floor screed. The house was completely emptied, but the floors were kept on the upper floors along with all the beams.


BCB: How did you programme the different stages of the renovation work given the time required for hempcrete to dry?

ST: The main work stages were straightforward. We started by laying the hardcore layer and the hempcrete screed. The builder then stepped in before we sprayed the insulating lining.

The insulating screed

More specifically, the earthwork contractor laid the pozzolana hardcore layer over part of the ground floor area following my instructions. The other part of the ground floor area covered in cement floor tiles was left as it was to avoid unnecessary demolition work.

Several drains were installed to ensure the hardcore layer would be well ventilated, with a system that ran right up to the rooftop to create a natural flow of air from the bottom to the top of the building.

The 17 cm thick hempcrete screed was left to dry. Once dry, we tiled it with traditional Pauzat terracotta tiles.


While the screed was drying, we got on with other work at the site:

  • The roof was insulated.
  • The mason created new openings and stripped the internal walls.
  • The house was entirely rewired.
  • Conduits and pipes were installed at the same time, with piping for the cast iron radiators on the upper floors and for the underfloor heating on the ground floor.
  • Preparations were made for the insulating lining by installing a secondary framework, along with framework for the openings.


The indoor insulating lining

We sprayed an 8 cm thick layer of Tradical® Thermo plus Chanvribat® Hempcrete on ground floor walls and on the inside of external walls on the upper floors. The output for this type of work is 2 m3 per hour, i.e., 10 m3 per day. To make sure we had the right settings for everything to work properly, I added a flow meter at the start of the pipe which carried the milk of lime.

Hempcrete is cast from the bottom upwards. You wet the substrate using milk of lime and then spray a first layer of hempcrete to obtain a surface that’s uniform. You then spray another layer up to the pre-defined thickness. The final touches are made using a 1.4 m long serrated darby and with the help of the pre-installed guides.


BCB: When did you start work on the finishes?

ST: After a month of drying, part of the lining was ready to be coated with a traditional lime render – consisting of a base coat and a lime plus sand dubbing out coat (sprayed on using the same machine) – made with Tradical® Bâtir and local Cadeuil sand, whose colour ranges from ochre to red depending on where it was extracted. It’s a well-graded sand with a particle size of 0/3.

We then chose finishes depending on the look to be created in each room. In most rooms we applied a thin lime-based Tradical® Décor finishing render for a fine-grained, floated finish. In the hall, we finished the walls with a super-thin lime render, Tradical® Finilys, applied al fresco as a single coat (smooth finish) or in two coats (burnished finish).


Lime and hempcrete project profile

  • Project owner: Private individual
  • Location: Charente-Maritime
  • Builder: AC Déco, 16 rue du Bosquet, 17250 Sainte Radegonde, France ||


Lime and hempcrete technical solutions

1- Hempcrete insulation

  • Hempcrete insulating lining: Tradical®Thermo + Chanvribat® | Density = 280 kg/m3
  • Hempcrete insulating screed: Tradical®Thermo + Chanvribat® | Density = 325 kg/m3
  • Tradical®Thermo and Chanvribat® is an approved lime and hemp blend that complies with the performance requirements of French professional rules for the construction of hempcrete structures.
  • Chanvribat®is a Granulat Chanvre Bâtiment certified hemp product.


2 – Traditional lime preliminary render


3 – Lime finish

  • Tradical®Décor, a ready-to-mix thin air lime render for creating a thin finishing render. For this project it was applied on a perfectly smooth Tradical® Bâtir plus sand brown coat.


4 – Decorative finish

  • Tradical®Finilys: a super-thin ready-to-mix lime render applied as a single coat for a smooth finish
  • Tradical®Finilys: a super-thin ready-to-mix lime render applied in two coats for a burnished finish


Interested in learning more about Tradical?

BCB Tradical®:

More examples about hempcrete homes and buildings

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