Frequently asked questions
Prices, thicknesses, performance, lead times: the questions we are asked most often, with figures from our own sites. Every project remains different — the quotation always sets out your case.
Expect around €115 to €150 per m² excluding VAT for a 10 cm thickness, including framing, projection and installation. The price depends on thickness, substrate, accessibility and application rate: every project is different. CARTDESIGN issues a detailed quotation within 48 hours.
Thermal performance depends first on the in-place density, then on the binder/hurd ratio, the application method (projected, cast, prefabricated) and moisture: there is no single value.
| Thickness | Thermal resistance R (m²·K/W) | U (W/m²·K) |
|---|---|---|
| 6 cm | 0.60 | 1.67 |
| 10 cm | 1.00 | 1.00 |
| 11 cm | 1.10 | 0.91 |
| 20 cm | 2.00 | 0.50 |
| 30 cm | 3.00 | 0.33 |
| Thickness | Thermal resistance R (m²·K/W) | U (W/m²·K) |
|---|---|---|
| 6 cm | 0.55 | 1.83 |
| 10 cm | 0.91 | 1.10 |
| 20 cm | 1.82 | 0.55 |
| 30 cm | 2.73 | 0.37 |
In a roof or light insulation (250 to 300 kg/m³), λ drops to about 0.06-0.07 W/m·K: resistance is higher at the same thickness. At equal density, hemp-clay insulates slightly less than hemp-lime but offers more thermal inertia and better hygric regulation. At 6 cm, both act as a thermal corrector rather than insulation.
The projection rate is 3.5 to 10 m³ per day depending on the technicality and accessibility of the site. At a 10 cm thickness, 100 m² represents about 10 m³ — that is 1 to 4 days of projection with the mobile unit and two operators.
After projection, allow 6 to 10 weeks of drying before any finish, and longer for thick layers. Ventilation and heating of the room during drying are the client's responsibility.
Yes. Hire of the biobased projection unit is €1,800 per day excluding VAT. The unit projects up to 10 m³ per day, with 25 m of hose and a possible 5 m extension. At least two independent 16 A circuits are recommended.
The CINVA RAM press costs €3,200 excluding VAT and is made in Belgium. Working as a team, it produces about 50 compressed earth bricks per hour from earth, sand and lime sourced on site. Once you own the machine and use the earth from your own site, the brick costs nothing more: the €6.50 per unit applies to bricks produced and supplied by CARTDESIGN.
Yes: a one-day introduction to biobased building, €550 per day, individually or in a group of up to six people.
Around €195/m² without cork insulation. Every project is different: the price depends on surface area, thickness and substrate.
Travel is charged per kilometre, round trip from our workshop in Les Waleffes, depending on the vehicle used: €0.55/km in a van (category B licence), €0.85/km in a van with trailer (BE licence) and €1.20/km in a truck (C licence). The amount remains an estimate, confirmed in the quotation according to distance and number of journeys.
CARTDESIGN builds larch saunas from €9,500, excluding the wood-burning stove. Every sauna is unique: it is designed on request, according to the client's needs and the dimensions of the space.
These orders of magnitude come from our sites and quotations. Every project is different: the detailed quotation sets the final quantities and price.