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Chimneys
Re-pointing the mortar joints on the stack
If you notice that the mortar between the bricks on the chimney stack has perished
it should be replaced. Failure to do so could result in rain penetrating the brickwork,
and damaging the mortar further. Remove any cracked or crumbling mortar. The stack
is now ready for pointing.
Resetting Chimney Pots
It is important to support the chimney pot before removing the flaunching, especially
if you are resetting rather than replacing the pot. Flaunching is the mortar base
holding the chimney pot in position on top of the chimney stack. Tie a length of
rope around the top of the pot (A) and a second rope around the chimney stack (B).
Then secure by attaching a rope from A to B on both sides of the stack. This should
hold the pot in position before removing the flaunching.
Use a cold chisel and club hammer to remove the mortar. If the base of the pot is
square, it is designed to fit over the flue exactly. If the pot does not fit exactly
or has a different shaped base, then the pot will need supporting before replacing
the mortar base. Use strips of slate strategically placed around the base of the
pot to support it in the correct position. Brush away any unwanted material and
dampen the surface of the stack. This is necessary, especially in warmer weather,
to stop the mortar from losing moisture too quickly, which would result in cracking.
Use mortar consisting of approximately a 1:4 cement:sand mix to replace the flaunching
around the base of the pot.
Replacing Chimney Pots
It is important to support the chimney pot before removing the flaunching. Flaunching
is the mortar base holding the chimney pot in position on top of the chimney stack.
Even though the pot will be discarded once removed, it can damage other areas of
the roof if it is not taken down carefully. Tie a length of rope around the top
of the pot (A) and a second rope around the chimney stack (B). Then secure by attaching
a rope from A to B on both sides of the stack. This should hold the pot in position
before removing the flaunching.
Use a cold chisel and club hammer to remove the damaged mortar. Untie the ropes
and remove the pot. The new pot needs to be placed in a central position to fit
the flue. If the base of the new pot is square, it is designed to fit over the flue
exactly. If the new pot does not fit exactly or has a different shaped base, then
the pot will need supporting before replacing the mortar base.
Use strips of slate strategically placed around the base of the pot to support it
in the correct position. Brush away the unwanted material and dampen the surface
of the stack. This is necessary, especially in warmer weather, to stop the mortar
from losing moisture too quickly, which would result in cracking. Use mortar consisting
of approximately a 1 : 4, cement : sand mix to replace the flaunching around the
base of the new pot.
Sealing the Flue
An unused flue can be draughty and allow rain to enter the stack. If you have no
intention of using the fire place and chimney facility, it is possible to seal the
flue. However care must be taken to allow ventilation inside the stack to keep it
dry and avoid a build up of dampness due to possible condensation.
There are two main methods to seal the flue correctly:
- Ventilator caps
There are two types of ventilator caps available. There is a metal cap, which clips
into the chimney top. This is a very simple ventilator to fit. The second type is
made of clay. This type needs mortar to set it in position in the chimney pot.
- Use of airbricks
Alternatively, remove the pots and remove a brick from both sides of the stack.
They should be removed on opposite sides, as they will then be replaced with airbricks,
which will allow the air to pass through freely.
Replacing the chimney flashing
Check for evidence inside the home around the chimney breast walls or on the upper
floor ceiling below the chimney stack for signs of dampness. Dampness in these locations
could mean the flashing is worn and needs attention.
Chimney flashing is quite difficult to repair/replace as it is fitted in four sections.
The slanted sides need stepped flashing, while the top needs a back gutter and the
bottom requires an apron.
- Apron flashing
The apron lies at the foot of the stack and should be the first section to be replaced.
It is made in one piece and secured with lead tacks to the top of the tiles.
- Stepped flashing
The stepped flashing is used on both sides of the stack. The sections are tucked
into the mortar horizontally between the brickwork at the base of the stack, where
they cover the soakers. Soakers are separate small pieces of lead or zinc that are
used to weather between the wall and the roof covering. The size of the soakers
will vary according to the type of tile or slate used on the roof.
If the old flashing sections have been removed, then the tiles on both sides have
been removed first to allow access to the stepped flashing. To replace this section,
lay it underneath the tiles on the side of the stack but over the front apron. Mark
its position against the brickwork and mark on the mortar joints. Fitting new lead
stepped flashing will give long-lasting waterproofing as well as the most attractive
finish to the roof. Point all flashing with a sealant. Repeat the procedure on the
opposite side of the stack.
- Gutter flashing
The final section to be fitted is the gutter flashing at the top end. This is normally
one piece that sits over the end of the step flashing.
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