Calculating the amount of loam for isolation
By calculating the volume (of hollow half dome) we can calculate the necessary number of litres (volume) of loam mortar. The volume of the loam layer is calculated by subtracting the volume from the half dome with the volume of the hollow part. This becomes clear when using the following formula: Volume = (D³ - d³) x (3,1416 / 12), with D = outer diameter and d = inner diameter.
If you have calculated the volume in cm³ then you have to divide the result by 1000 to get the volume in litres. Multiply the necessary volume by the number of litre components knowing that you need for approx. 1 m³ (1000 litres) loam mortar and a proportion 3 : 1/2 : 1 : 1 :
- loam soil: approx. 860 litres
- chaffed lime: approx. 140 litres
- Rhine sand: approx. 285 litres
- Chopped straw: approx. 285 litres
- (Horse urine: approx. 14 litres)
Example (by means of building plan):
- d = 140 cm (this is the length of the oven (100 cm) + 2 x the thickness of the vault)
- D = 160 cm (this is 140 cm + 2 x the thickness of the loam layer)
- Volume = (D³ - d³) x (3,1416 / 12) = (160³ - 140³) x 0,2618 = 353953,6 cm³
- 353953,6 cm³ = approx. 350 litres of mortar
- Loam soil: approx. 860 x 0,35 = approx. 300 litres
- Chaffed lime: approx. 140 x 0,35 = approx. 50 litres
- Rhine sand: approx. 285 x 0,35 = approx. 100 litres
- Chopped straw: approx. 285 x 0,35 = approx. 100 litres
- ( horse urine: approx. 14 x 0,35 = approx. 5 litres)
With 1 m³ (1000 litres) of loam mixture, you can cover up to 10 m² with a layer of 10 cm thick.