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For medium duty applications
it is better to consider
metal cavity fixings as they
transfer the load behind the
plasterboard and the stresses
are put on to a wider area of
the board. The load capacity is
then determined not only by
the strength of the fixing but
the strength of the board itself.
There are generally two
common types of metal cavity
fixings available, either toggle
or umbrella types. Toggles come
in various designs, supplied with stud or hook end. The toggle itself
can be either gravity or spring type as illustrated by the examples
above.
Toggle fixings derive their strength from the exceptionally broad
splay of the toggle within the cavity, helping to spread the loading permanently expanded and therefore, while the screw is removable
on the plasterboard. The drawback with these types of fixings is that the anchor body is extremely difficult to dismantle at a later date. For
they require a relatively large drill hole to accommodate the size of this reason it should not be used for applications where fixing removal
the toggle. Also some toggles are supplied with a pan-headed bolt is required in the future.
instead of stud and nut, which means that they need to be assembled Umbrella type fixings can be expanded by either using a
to the fixture prior to installation and if the screw is withdrawn, the screwdriver or, for high volume jobs, installation pliers.
toggle falls down within the cavity. For heavier applications where There are on the market also very specialist adhesive plasterboard
large gravity toggles are specified, the required cavity depth must be fixings, which require a special element to be inserted and filled with
observed as 70mm - 75mm free space might be required for a large injection resin, to create a form-lock behind the plasterboard. These
toggle to be inserted behind the board. systems are more complex and cannot be loaded immediately as the
The steel expanding umbrella type of fixing is also very strong, curing time of the resin must be observed.
limited only by the fact that it doesn’t For heavy duty applications where the strength of the plasterboard
spread out as much as the toggle type. It is not sufficient, other methods of anchoring should be used. For
has the advantage that it can be placed partition walls it is possible to fix directly into vertical wooden or
in the drill hole before offering up the metal stud using self-drilling screws, providing the fixture can be
fixture, making installation that much positioned in an area where these studs are located.
easier. It also allows the fixture to be If it is a new build, it is also possible to install timber battens
demounted and refitted again very easily in the cavity where these heavy items will be fixed. For dry-lining
without losing the fixing in the cavity. The applications with block wall behind, the loads can be transferred to
disadvantage is that this type of fixing is the block by simply using long nylon plugs called “frame fixings”.
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