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Preparation and
repairing surrounding brickwork
Regardless of the type of cast iron air brick
being installed, the first step is to remove the
old or damaged air brick, clean off the old
mortar and clean out the hole. Once clear,
examine the adjoining bricks and decide if they
need replacing or if loose, if they need to be
mortared back in place.
The brick in the example arrowed below is "spalled"
and the surface is severely eroded and needs
replacing.
If the mortar is lime based it will be easy to
remove.
Use a 10-15mm masonry drill bit and drill out
corners and then run drill along length of
mortar till the brick is loose and can be pulled
out by hand.
Sweep loose mortar away and check replacement
"reclaimed" brick fits.
Use a brush to wash away dust prior to fitting
new brick and mixing mortar
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Mortar for
Period Properties for
installing cast iron air bricks
Below is a mix suitable for installing cast iron
air bricks and repairing adjacent bricks in most
pre Edwardian lime/cement mortared brick
properties including grade 2 listed properties.
This mix is strong enough to adhere the
iron of the air brick to the bricks themselves
without damaging them - Mixes with too much
cement and not enough lime could cause early
failure of surrounding brickwork and keep
moisture from evaporating out of the mortar
leading to damp problems or early brick failure in the future. A
mix without cement and just hydraulic lime and
sand may be suitable for brickwork but it is
unlikely to be suitable for installing the cast
iron air brick as it could take months or even
years to set.
Please consult with your local authority
conservation officer especially if your property
is grade 2* or grade 1 listed.
mix here was in the proportion 1:1:5
which is 1 part cement, 1 part hydraulic lime
and 5 parts sharp sand
Please note. This mix is for the installation of
cast iron air bricks and is not recommended for
general pointing.
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Preparation and
repairing surrounding brickwork
With the surrounding area cleaned, dusted and
wetted, lay mortar and point in the replacement
brick and point.
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Of the many
sizes and designs of cast iron air bricks available, there
are only two different types on the market
- those with depth and those without. Those with
depth (either with wings or with a boxed section
reverse) are the easiest to install as
replacements while those without depth (with a
cutaway reverse) require a little more care but
are cheaper and have a larger range of designs.
Below we take a look at installing the two
different types and feature actual cast iron air
brick replacements for single brick size 9" x 3"
and the double air brick size 9" x 6", the two
most common sizes installed in houses across the
UK.
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Cast Iron Air Bricks shown are
supplied from
"The Cast Iron Air Brick Company"
tel. 01507 602004 or see
online
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| Installing Cast Iron Air
Bricks with Boxed Section Reverse |
Installing Cast Iron Air
Bricks with Cutaway Reverse |
| These examples
of installation apply to any size of cast iron
air brick. The example below is a 9" x 3". |
Boxed section reverse has depth and a boxed
frame which helps provide a framework to adhere
mortar onto it and the adjoining brick work.
Heavy duty cast iron air bricks and also
those with wings also have surfaces on the
reverse to help key the cast iron to the
adjacent brick work they are especially secure
once the mortar has set. |
The cutaway reverse requires more careful
installation and is not as secure as the boxed
section reverse or cast iron air bricks with
wings or the Heavy duty type. It is not ideally
suited for areas which are close to the pavement
as it is likely to become dislodged if it is
kicked by pedestrians. |
1. lay a bed of mortar along the base and on the
edges.
2. Place air brick
3. Point in
4. Use mortar board, lay a length of mortar on
trowel and feed into gaps
5. Finish off
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1. lay a bed of mortar along the base and on the
edges.
2.
Secure the cutaway reverse in the vacant hole
utilizing removable wedges or card as shown
below (or jam in place using permanent small
pieces of broken brick)
2. Tradesmen in Georgian, Victorian and
Edwardian periods would have used traditional
materials for packing and we would advise to use
the same. Slate is a fairly obvious choice
although wooden wedges and even flat shells and
pieces of brick will also work well.
It is important to pack the material between the
cast iron and the brick so the air brick is
firmly held but without too much pressure
otherwise the cast iron may crack. Hammer the
packing in, ensuring the cast iron air brick
isn't struck with the punch or the hammer
otherwise it may fracture and finally remove any
protruding packing so the mortar can be pointed
over to hide it.
3.
Point in around the edges and along the bottom,
removing and discarding the packing material if
it is protruding or better still point over it
and incorporate it into the joint .
4.
Point along the top last, being careful not to
force too much mortar into the void - ensure the
holes are kept clean by clearing them with a
pencil or old drill.
5. Finish Off |
The finished air bricks - Once completed it is
impossible to tell which are boxed section
(right) and cutaway reverse (left)
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Heavy
Duty Installation
The wings on these heavy weight cast iron air
bricks are ideal to support brickwork above.
In the example below the original air brick has
been installed supporting the full brick above
which now also needs replacing as well as the
cast iron ware.
Insert cast iron air brick resting on a bed of
mortar.
Lay narrow layer across iron ware and position
replacement brick.
Finish off by pointing around edges and along
the top.
Any mortar dropped down and blocking holes
should be pushed out of the way or vacuumed
while still wet.
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Finishing Off
As soon as you have finished give the air brick
a wipe over with a damp sponge and gently remove
any mortar from the metal.
After a couple of days poke through the holes to
ensure all the large pieces of loose mortar are
away from the vent holes.
Now lightly scrape with a wire brush across the
mortar pointing to bed it in and remove any
excess.
If the cast iron air bricks are lacquered and
all the mortar was sponged off they should just
need a buff up with a polishing cloth or duster.
If they are bare metal just leave them to
develop a light rust - this will protect the
iron air brick. If you have any scratches
just touch them up with automotive spray paint
or Hamerite smooth (mask off the mortar and
surrounding brick work for a neat finish.
If you have installed cast iron hit and miss
vents then we recommend spraying them
periodically with preservative such as WD40 to
ensure they remain operational - they shouldn't
be painted.
On no account should cast iron be painted with
water based paints or emulsion.
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