Sound Insulation

Sound insulation value of brick walls

Average sound reduction



Half-brick wall, unplastered Half-brick wall


plastered both sides One brick wall


plastered both sides


Cavity wall of two half-brick skins with butterfly wall ties not more than one per yard. Wall plastered both sides


Aperforated 'through the wall, unit of 175mm width weighing 396-496 kg/m2; when plasteed both sides, such as is fairly widely used in party wall construction


one and half brick wall



    1) The values assume brickwork of about 1850
    kg/m3 weight.

    2) The cavity wall value would be less if rigid
    wall ties were used.

    3) The values given are average over a normal
    frequency  range  and  for  reasonable
    standards of construction. As explained in
    Part 2, in-use values may vary considerably.

Moisture Movement

The moisture movement for calcium silicate bricks ranges:

      Reversible                   Irreversible

      0.001-0.05                   0.001-0.05

Water Absorption

Geerco water absorption test results are based on total immersion of the test samples, in water, for a period of 24 hours.

Absorption of Geerco bricks (by weight)

                                             Minimum   Maximum     Average
Sandlime Bricks                          7%          13%            10%

Two important factors which affect the water absorption rate and therefore the resistance to water penetration are the size and distribution of the brick pores. The pores in the bricks are so numerous and consistent that the complete filling of each pore is unlikely. This limited porosity can be advantageous.

Thermal Expansion

The linear Coefficient of thermal expansion for calcium silicate bricks is about (0.000008 to 0.000014) per degree celcius for vertical direction, and 0.0000056 per degree celcius for horizontal direction.

Driving Shrinkage

Geerco bricks comply with the shrinkage requirments of BS 187 ranges between 0.01% to 0.035%

Virtually all building materials expand or contract and bricks of all types are no exception. Such minor movement is, if necessary, easily compensated for in the correctdesign, storage and use of the material, and is not considered synonymous with cracking in brickwork.

The drying shrinkage of bricks situated in permanently damp conditions, below d.p.c, for example, is of no significance

Fire Resistance

Test on calciumn silicate bricks set in cement mortar, carried out in accordance with BS 476, have proved that they provide adequate fire resistance.

Under actual fire conditions, calcium silicate brickwork has been found to have good fire resistant properties, preventing it spread, hence lessening the chances of collapse of the structure, often surviving well enough for continued use when a structure has been otherwise burnt out.


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