12
Wall preparation for flue tube.
The flue must be installed so that it is at right angles to the back panel of the fire all
round the flue circumference. The fire itself should be fitted vertically against a flat
wall. Where this is difficult to achieve due to building inaccuracies care should be taken
to ensure that the back of the fire is not stressed in any way due to distortion of the
assembly when tightening the fixing screws. Where necessary, non-combustible packing
pieces should be used to provide a satisfactory fixing surface.
Before cutting the hole in the wall make sure that the height to the top surface of the
finished floor is known. The height from this surface to the flue hole centre is shown
in figure 13.
If a loose hearth or plinth is to be used, the height from its top surface must be used
when determining the flue height.
Place dust sheets on the floor and over any furnishings etc.
Make sure that the centre of the flue hole is as shown in figure
13.
Now cut the hole for the flue unit.
Core drilling
Drill a pilot hole through the wall. Inspect the hole to ensure that it is in the brickwork
and not in mortar. If it is in mortar, it is advisable to reposition the hole approximately
25mm away (Ensuring that all other clearances to firebox are complied with.).
Remember to reposition the screw fixing holes.
Drill the flue hole with a 5in. (127mm) core drill.
Remove any combustible wall cladding material from the area behind the firebox as
described previously.
Hammer and chisel cutting
Mark a 127mm (5in) diameter circle for the flue hole. Chisel out the area marked.
It may be necessary to make good both the internal and external wall faces. To achieve
a neat finish and to make any future removal of the flue unit easier, it is recommended
that a cardboard cylinder is formed around the flue unit and inserted in the hole whilst
making good. Remove the cardboard cylinder after making good.
Combustible walls (wood, fibreboard,
plasterboard etc.)
Building regulations require that the outer surface of the
flue tube and terminal must not be closer than 25mm to
combustible material and must be lined with steel sleeve not
less than 0.5mm thick. (see figure 12). The sleeve can be
made by coiling a piece of sheet steel to between 125mm &
127mm outside dia.and fitting it to the combustible parts of
the construction.
Mark out and cut a hole 177mm diameter through the
plasterboard. Cut a hole of about 165mm in the vapour
barrier. Clear the insulation quilt from the hole area and cut
a 177mm dia. hole in the timber sheathing and breather
paper. Drill a 127mm diameter hole through a non-
combustible (brick etc.) outer wall.
Fit the steel sleeve. The sleeve should not protrude more
than 10mm into the cavity. The sleeve should be sealed to
the inner leaf of the wall at both ends with a non-setting
thermal mastic sealant.
If the outer wall is combustible drill a 177mm hole and fit
the liner sleeve through to this wall.
Cover the hole with a steel plate size 500mm x 235mm, not
less than 1.5mm thick with a 127mm diameter hole in the
middle. Fix with suitable screws and plugs.
Where the whole wall is of combustible material a non-corrosive plate 455mm square
with a 127mm diameter hole in the centre must be fitted to the outer face of the wall.
Fig. 12