Underpinning to Walls ~ to prevent fracture, damage or settlement
of the wall(s) being underpinned the work should always be carried
out in short lengths called legs or bays. The length of these bays
will depend upon the following factors:-
- Total length of wall to be underpinned.
- Wall loading.
- General state of repair and stability of wall and foundation
to be underpinned. - Nature of subsoil beneath existing foundation.
- Estimated spanning ability of existing foundation.
Generally suitable bay lengths are:-
1„000 to 1„500 for mass concrete strip foundations supporting
walls of traditional construction.
1„500 to 3„000 for reinforced concrete strip foundations
supporting walls of moderate loading.
In all the cases the total sum of the unsupported lengths of wall
should not exceed 25% of the total wall length.
The sequence of bays should be arranged so that working in
adjoining bays is avoided until one leg of underpinning has been
completed, pinned and cured sufficiently to support the wall above.
Underpinning