Building with Earth: Design and Technology of a Sustainable Architecture

Application

Before applying the plaster, the loam sur-

face should be moistened and primed with

lime-casein milk. The plaster is then applied

in two layers, bringing the total thickness up

to a maximum of 20 mm. In the first layer,

some cement can be added for faster cur-

ing. The second layer should be applied

while the first is still slightly moist. When

shrinkage cracks occur, these should be

moistened with a brush dipped in lime milk

and then closed by rubbing with a trowel.

It should be noted that lime plasters cure

when in contact with carbon dioxide from

the air, and this process is only possible in

the presence of sufficient moisture. There-

fore, walls should be sheltered from direct

sun and wind, or kept moist with a damp

fabric.

Internal plasters can be applied in one layer.

Gypsum plaster or gypsum-lime plaster,

with or without casein, can also be used in

internal work. Cement plasters, however,

should not be used even for internal work.

Effect on vapour diffusion

The effect of adding double-boiled linseed

oil and casein on reducing the vapour diffu-

sion of lime plasters was tested at the BRL.

The values of the vapour diffusion resistance

coefficient μ obtained are listed in table

12. 6.

Shingles, planks and other covers

Besides plasters and coatings, shingles,

planks, larger covering panels or baked brick

walls separated by an air cavity can be used

to protect loam walls. These methods are

especially useful if additional thermal insula-

tion is to be applied from the outside.

A common method is shown in 12. 7. In

Mesopotamia (Iraq), layers of glazed baked

bricks have sheltered adobe walls for thou-

sands of years. It is always advisable to

separate such covering layers from the wall

with an air cavity, so that rain that pene-

trates can drain out and does not harm the

wall.

Structural methods

Protection from rain

One method of preventing rain from com-

ing into contact with a loam wall is to pro-

vide it with a roof overhang. A sufficiently

high plinth (30 to 50 cm) can protect from

splashing rain. The joint of the wall with the

plinth has to be carefully designed so that

the rainwater can flow down unhindered

without entering the joint between wall and

plinth. In 12. 8, solution A is unacceptable.

Solutions B and C may be acceptable in

areas with little rain. Solution D is common,

whereas E and F show perfect designs for

combating this problem.

Protection against rising damp

Exterior loam walls have to be protected

from rising damp in the same way as baked

brick or stone masonry walls. A damp-proof

course, usually bituminous felt, and some-

times plastic or metallic sheets are used.

As these means are fairly expensive in the

developing world, a 3 to 4-cm-thick rich

cement concrete layer is often used as an

alternative. This should be impregnated

with bitumen or waste mobil oil.

Protection against flooding

In kitchens and bathrooms, the plinth should

have a waterproof skirting of tiles, slates,

rich cement plaster etc. The skirting design

should prevent water from leaking or bro-

ken pipes, which could flood floors, from

reaching the loam wall.

103 Weather protection

12. 
    

    6

    
    


13. 
    

    8

    
    

Lime

1 – 1 1 1 1

1. 5

Trass-

lime

• 1 – – – – –

Sand

3

3

6

15

3

3

10

Fat-free

cheese

• 
  


• 
  

  0.5
  0.5

  
  


• 
  

  0.25

  
  


• 
  

Linseed

oil

• 
  


• 
  


• 
  


• 
  

  0.05
  0.05

  
  


• 
  

Clayey

loam

• – – 3 – – 2

Cow-

dung

• – – – – – 6

μ-value

11. 2
    10.8
    6.2
    9.7
    15.2
    28.5
    8.0