12 issue 5
12.flue and builders opening requirements
Prior to creating the builders opening the flue must be checked.
No restrictor plate or flue damper is permitted.
The flue must be swept prior to installation.
The flue must be free of any obstructions.
The flue must be checked to ensure it
only
serves the fireplace opening to be used for the fire.
The flue must have a positive up-draught and checked as follows before the builders-opening is constructed:
Before installing the fire a simple smoke test should be carried out on the flue to check its condition. Light a smoke
generator, hold it at the top of the fireplace opening and observe that the smoke is being drawn up the flue, if so, proceed
with installation. If not, pre heat the
Flues for a few minutes and recheck, if smoke still fails to be drawn up the flue, further
Investigation is required and the appliance
MUST NOT BE FITTED
.
The effective height of the flue must be at least 3 metres
A
Purpose Made Builders Opening With a Conventional Stone Flue.
With a minimum cross sectional dimension of 175mm (7”) and a
minimum effective height of 3 metres.
Fig 12:1a
shows the minimum
and maximum sizes of the builders opening.
The base of the builders opening must be a non-combustible material
and at least 12mm thick. The Builders Opening must be at least
300mm off the floor for a wall mounted fire installation.
It is recommended that a qualified builder construct the builder’s
enclosure.
A lintel should be used to support the chimney breast above the
Builders opening.
Any gaps around the Builders Opening as may be the case
With a dry liner wall must be sealed.
12mm
min
300 mm min
flue
Fig 12:a
Opening sizes
See page 11
B
Additional Requirements for a Purpose Made
Builders Opening below a Flexible Flue Liner.
A 125mm (5”) diameter flexible gas flue liner
Conforming to B.S 715, and connected to a
Register Plate fitted and sealed above the Builders Opening.
See
Fig 12:1b
floor
Register plate
Fig 12:1b
Flexible flue liner
300mm min
340mm min single trim version
