critical is that the bottom timbers be placed so they
rest evenly and firmly on the ground.
Cribbing is desirable when lifting loads by jacking
stages. This procedure requires blocking to be placed
under the jacks, lifting the load to the maximum height
the jacks can safely accommodate, placing the
cribbing under the load in alternating tiers, with no
personnel under the load, and then lowering the load
onto the cribbing.
When cribbing is not high enough or at the correct
height, build up the blocking under the jacks until the
jacks can bear against the load while in their lowered
position. Raise the jacks again to their maximum safe
height and lower onto the added cribbing. This
procedure can be repeated as many times as necessary
to build up the cribbing to the desired height.
The term scaffold refers to a temporary elevated
platform used to support personnel and materials, for
immediate usage, throughout the course of
construction work. You will use scaffolds in
performing various jobs which cannot be done safely
from securely placed ladders. We will take a brief look
at a few of the different types of scaffolds which you
will need from time to time on the job.
Planking and Runway Scaffold
A planking and runway scaffold shown in
figure 6-38 consists of single scaffold planks laid
across beams of upper floors or roofs. It is frequently
used to provide working areas or runways. Each plank
should extend from beam to beam, and not more than
a few inches of the planks should extend beyond the
end supporting beam. A short overhang is essential to
safe practice to prevent personnel from stepping on an
unsupported plank and falling from the scaffold.
Planks should be thick enough to support the load
safely and applied without excessive sagging. When
the planking is laid continuously, as in a runway, make
sure the planks are laid so that their ends overlap.
Single plank runs may be staggered with each plank
being offset with reference to the next plank in the run.
Swinging Platform Scaffold
The most commonly used type of swinging
scaffolding is the platform scaffold shown in figure
6-39. The swinging platform scaffold consists of a
frame with a deck of wood slats. The platform is
Figure 6-38.A planking and runway scaffold.
supported near each end by iron rods, called stirrups,
which have the lower blocks of fiber line fall attached
to them. This tackle arrangement permits the platform
to be raised or lowered as required. The tackle and
platform are supported by hooks and anchors on the
roof of the structure. The fall line of the tackle must
be secured to a part of the platform
position to prevent it from falling.
when in final
Figure 6-39.A platform scaffold.