1) There are several reasons for transferring levels in construction, including establishing excavation depths, ensuring materials like concrete are laid accurately, and marking datum levels for bricklaying and formwork.
2) A datum peg set to a predetermined level like the damp proof course acts as a temporary benchmark from which levels are transferred around the foundation to control depths.
3) Levels can be transferred around the foundation manually using a spirit level and straightedge or via optical/laser levels, with the straightedge method requiring the level and straightedge to be reversed at each peg to cancel out errors.
3. Reasons for Transferring Levels
There are a number or reasons for the transfer of
levels in substructure work. These include:
To establish the level of the ground for
excavation (both oversite and trenches).
To ensure materials such as concrete and
hardcore are laid to an accurate level.
To establish datum for bricklaying, e.g. DPC
level.
To establish a level for concrete formwork, e.g.
when constructing a concrete raft foundation.
4. Transferring Levels from the
Datum to the Foundation (Strip)
During the process of setting out, a datum
peg is positioned to mark a predetermined
level, such as DPC or floor level, this is
called a Temporary Bench Mark (TBM)
This is the level from which the bricklayer or
ground worker will transfer levels helping to
control the depth of the foundations and brick
footings.
5. Datum Peg Spirit level and
straight edge
Gauge Rod or
tape measure
Concrete
thickness pegConcrete
thickness
Multiple of
brick courses
Transferring Levels from the
Datum to the Foundation (Strip)
6. Having set the first peg to gauge from the datum,
the level must be transferred all around the
buildings foundation to provide a guide for the top
of the concrete when poured.
Optical or laser levels are most commonly used to
do this. However, at times the, bricklayer will find it
more convenient to simply transfer the levels
around the trench by the use of a straightedge
and spirit level.
7. Using a Straight Edge and Spirit level
It is essential to REVERSE the level and straightedge
at each peg reading. This ensures that any
discrepancy in the straightedge or level is not
repeated at every peg, but cancelled out at every
other reading.
Datum peg
Depth to work brick courses
Spirit level and straight edge
8. Boning Rods
Another method of transferring levels
around a trench is by the use of boning
rods.
Boning rods are made from timber and are
usually painted so that they are easily seen.
Boning rods are typically used in threes, the
middle one being known as the traveller.
Boning Rods
Traveller
Levelling pegs