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- Knocking walls through is very hard and dirty
work. Make no mistake, this is one of my least favourite jobs.
- Before starting work of this nature, the size
of the opening must be determined as the finished size will be
below the RSJ (reinforced steel joist) which is sometimes called
an I Beam owing to the sectional shape of the steel resembling a
capital letter I. If you have a cavity wall to remove then
you'll need 2 RSJ's (one for each skin of brickwork). The size
of the RSJ must be determined by a complex calculation based on
the span, the load above, etc, A structural engineer will be
able to help with this but charges can vary so shop around.
- A hole will need to be made right through the
wall in order to accommodate the steel pins, which should be at
least 3 inches square in section and of adequate gauge. The hire
shop will supply these along with the Acro props which are
placed vertically under the pins to support. You'll find this
step easier with 2 people winding the Acro props at the same
time to take the strain. The props should be placed on baulks of
timber or thick planks which should span the timber floor joists
to spread the weight, unless of course you've got a concrete
floor.
- Once the pins are secure, you may remove the
brickwork underneath using a hammer and chisel or electric Kango
if the brickwork is stubborn. You may need a skip for the bricks
and rubble.
- 2 RSJ's side by side should be bolted
together. Normally the steel stockist will offer a hole drilling
service and provide the nuts and bolts along with spacers so
that the correct cavity can be set. When ordering, you'll need
to know the overall width of the wall. Bricks are 112.5mm and
the cavity is a variable. Knocking a test hole through will
assist with this question.
- The width of the opening will determine the
number of pins required. As a rough guide a 2 metre opening will
need 2 pins, a 3 metre opening will require 3 pins etc etc. The
pins nearest the ends of the aperture should be placed about
500mm from the end with any other pins placed equally spaced
apart.
- Once the pins are secured the RSJ's have to
be put in position and secured with 2 Acro props and wound up
tightly. The RSJ's must have at least a 150 mm column (better if
they have 200mm) to support each end. The ends of the RSJ must
have concrete pad stones cemented into position underneath for
support. Resting RSJ's on brickwork should be avoided as old
bricks may crumble.
- Any gaps between the top surface of the RSJ
and the brickwork above can be filled with slivers of roofing
slate tapped in with a hammer until solidly packed.
- Fill in any gaps with a mortar mix of 3 parts
sand to 1 part cement.
- After 24 hours, remove the props and pins
(again with 2 people otherwise one prop will fall when the other
one is loosened off).
- Lastly - call the plasterer.
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