A selection of 9"x6" cast iron air bricks
Period Air Bricks
Period cast iron air bricks come in
many different designs but often in just two standard sizes the 9"x 6" and the
ones shown above, the 9" x 3". The 9" x 3" is a typical
ventilation cast iron air brick and is more or less the size of a standard brick
so blends in nicely with the street scene. Often they would be sited at the
front and rear of a house at ground level at varying rates. Small terraces would
normally have one or two at the front and the same at the back, larger
properties utilising additional grilles under the hallway and additional air
bricks fitted at the rate of one per metre.
It should be noted that cast iron air bricks from Victorian
and Edwardian periods were manufactured to varying standards and designs .
Although their external dimensions were standardised the free air flow through
the air brick varied widely with some providing very little air flow making them
The "4 star" cast iron air brick design above is
an example of a poor design - even brand new or cleaned out, this air brick at
best could only achieve a free air flow of 1500mm2 as by design it has
significantly more metal than holes. This is about 1/3 as efficient as the
period example below and the two modern replacements which all achieve around
Below we take a look at a standard
designed Victorian cast iron air brick and compare its dimensions and
specifications to a modern replacement.
The type above, known as "12 Tees" by
way of its "T" pattern of six along the top and 6 along the bottom has excellent
free air flow and would have been used singularly or doubled or tripled to
provide for larger vents as 9" x 6" or 9" x 9". It was predominantly used as sub
floor ventilation in brick houses to vent below wooden floors to reduce damp and
prevent rot (especially dry rot).
Seen below against two modern reproductions, it is clear to
see although the patterns are different , the design remains principally the
same the design.
The top air brick is a Windsor (item WIN3) vertical slotted and the
bottom, a grid pattern (Item GRID3), both supplied by....
Cast Iron Air Brick Company"
Photographed from the underside.........
Period Cast Iron Air
Bricks and Modern Replacements
||9" x 3"
||8 1/2" x 3"
|Depth of Wings
|Free Air Flow
& Floor Grilles
Below - See the huge range of cast iron floor grilles and vents on the cast iron
air brick company website,
Floor Grates are suitable for orangery's, churches and conservatories.
Below - Hit and Miss cast iron
air bricks allow controllable ventilation
Looking at these more closely, they were
designed for use as controllable ventilation especially for use with solid fuel
fires . When the fire was off they could be closed to cut down the draught and
once the fire was lit they could be opened again to allow air flow and improve
the "draw" of the fire.
The Victorian cast iron hit and miss air brick
was designed with fairly close tolerances to allow the grille to shut of the air
as much as possible but this has often led to many failing prematurely as they
are prone to seizing. With this in mind, the modern replacements are visually
similar and ideal replacements for house restorers but do not shut off the air
completely as they have very loose actions which significantly prolong the life
of the unit.
These hit and miss air bricks are suitable for
installation as adjustable ventilation providing fresh air to inglenook fires,
solid fuel fires and void spaces such as blocked off chimneys. They should never
be used for fresh air provision for any gas appliances or where paraffin heaters
Installing Cast Iron Air Bricks
for more details on installing cast iron air
bricks go to
Cast Iron Air bricks can be used as air inlets and exhaust
outlets in the following situations :-