Fire resistance

Fire resistance of masonry walls relates to fitness for use and is a property of the complete element of a structure. The period of fire resistance of a masonry wall is taken to be the time (from 30 minutes to 6 hours) from the start of the test to failure of stability and integrity.

All Hanson’s aggregate blocks have an A1 fire classification rating and have been tested to relevant British and European Standards. Notional periods of fire resistance for masonry walls to comply with Approved Document B (AD) are given in Table 14 of BS 5628: Part 3.

Criteria for fire resistance
This table takes cognisance of the relevant factors affecting the use of masonry units for fire resistance purposes. These are as follows: 

    a   The form of the units involved i.e. whether solid or otherwise 
    b   The thickness of the units involved 
    c   The aggregates used in the manufacture of the units, i.e Class 1 or Class 
    2 aggregates
    
Class 1 aggregates comprise limestone, pumice, sintered pulverised fuel ash, furnace bottom ash, foamed or expanded slag and various other types of aggregate. 
    
Class 2 aggregates, comprise all gravels and crushed natural stone, excluding limestone. 
    
In general tems, all lightweight blocks are made from Class 1 aggregates. 
    
The Evalast range of products may be produced from Class 1 or Class 2 aggregates depending on raw materials available in the manufacturing locality. It is advisable to check with Hanson’s Product Services department. 

    d   The function of the wall, i.e. whether loadbearing or otherwise 
    e   The construction of the wall, i.e. whether single leaf or cavity construction 
    f    Wall finish, i.e. whether plastered or otherwise and the type of plaster involved.

The fire resistance quoted on the individual product data sheets are based on:
 
    i Loadbearing or non-loadbearing 
    ii No finish 
    iii Made with Class 1 or Class 2 aggregate 
    iv Single leaf

For alternative forms of construction, please contact Hanson’s Product Services department.
 
In walls designed to resist fire, any movement control joints necessary should be  filled with a non-combustible material capable of accepting the anticipated movement and sealed with an appropriate material to give the same fire resistance as the blockwork.