Movement joints: Provision of
Brickwork Expansion Joints
Supported by
May 2014
Movement joints: Provision of Brickwork Expansion Joints:
Background:
Clay brickwork has to have provisions for
thermal expansion. Bricks expand irreversibly
for up to 20 years after they are removed
from the kiln. Most of the irreversible
expansion occurs within the first six months
after production. The supporting structure
often reinforced concrete or blockwork will
actually contract or creep and so
accommodation has to be made, for
differential movement by flexible wall ties or
movement joints. This advice is only
concerned with clay brickwork, other bricks
such as calcium silicate products do not
behave in the manner described below, the
advice is only relevant for current climatic
conditions in the UK.
Movement joints are not solely for expansion,
but also for contraction. In common with other
building materials, bricks will contract during
dryer colder weather. Brickwork must be
constructed to enable movement in both
directions to occur. Thirdly, joints can be
required to cater for differential movement and
frame settlement. Correct design is achieved
by following the advice within PD 6697 and
other sources such as this document. This
section will identify how to avoid stresses in
brickwork design and relieve potential issues
by correct position of movement joints.
It should be within the province of most
architects and certainly all structural engineers
to interpret the provisions of PD 6697. In
particular, they should select suitable positions
for movement joints. It is one of the benefits
of brickwork that there is no area that the
designer cannot understand and therefore the
designer does not require the advice of an
outside expert, although a checking procedure
with a second opinion is part of good practise.
Buildings prior to the 1890s were built in lime
mortar; lime mortar allows the provision of
movement
within
brickwork
allowing
expansion to take place. Brick buildings from
earlier periods have a greater degree of detail
and overhanging features as part of the detail
design of the building. The South elevation is
more onerous than other elevations. Modern
buildings tend to have cleaner lines, have less
2 | BDA Guide on the use of Movement Joints
overhanging and therefore, less shadowing so
there can be higher temperatures with
consequentially higher expansion in the
brickwork. It may well be that we are living in
a time of potential climate change, and higher
temperatures have been recently experienced
within the UK than it have been traditional.
Lambeth Palace
No provision of movement joints necessary with
heavy lime mortar structures slowly built.
This is of course not to say that there are not
movement joints failures; only the best
buildings survive. Prior to the provision of
cavity walls brickwork walls were generally at
least one brick thick 215mm, 327 or 440 wide.
The bricks were also under load, taking the
dead load from floors and roofs and internal
live loading the bricks being under
compression. If a brick is under compression
and fully loaded, its potential movement will
be restricted and therefore the provision of
movement joints may not be as essential.
This advice is concerned only with movement
provision for brickwork expansion. Additional
creep in reinforced concrete, compression or
shrinkage in other materials is in addition to
this advice. For example, brickwork supported
by a long span steel beam may have a
horizontal brickwork expansion joint of 10mm
for brickwork expansion. The beam has a
potential deflection of 15mm from the
designed loading. The total movement joint
will be 25mm. This may well cause visual
problems which have to be considered by the
designer. A potential solution for this horizontal
joint may be to corbel out a brick to place the
horizontal joint into shadow.
Movement joints: Provision of Brickwork Expansion Joints:
Flexibility and Wall Ties:
Movement and flexibility is required in all
building elements. Foundations settle and
respond to clay heave, steelwork expands and
contracts. Typically a timber frame will
contract by up to 6mm over a 2.5mm storey
height. Movement joints should be considered
in the light of other materials.
A brick panel should never be set into a rigid
frame, and movement should always be
considered and designed. Flexibility should
always be permitted with expansion and
movement possible. This includes the provision
of wall ties which while allowing connection to
an inner skin providing stability do allow flex
and movement between dissimilar materials
and internal and external temperatures. It is not
advisable that wall ties are too stiff restricting
movement. Wall ties should be installed to the
requirements of PD 6697. The minimum
requirement for a sheltered site is for ties to be
installed at 450mm centres vertically and
900mm vertically arranged in a diamond with
ties either side of the Movement joint within
225 of the joint and minimum 300mm
vertically.
Concrete blockwork will contract as the
product dries. Brickwork expands and so the
movement joints to blockwork and brickwork
needs to be staggered to avoid stressing the
wall ties. If a brickwork column or chimney is
built with an adjoining panel wall, they must be
separated by a compression joint allowing
movement tied appropriately. Different
thickness of wall may move differently and
require a joint between the elements.
MOVEMENT JOINT
1
22
225
225
225
225
1. Ties to within 225 of MJ at 300mm min. vertically
1
2. MJ normally compressible strip (to 50% thickness)
with mortar matching finish to face
Blockwork
contracts
Blockwork contracts
Blockwork expands
expands
Brickwork
MJ’s to brickwork and blockwork should alternate to avoid stressing wall ties
BDA Guide on the use of Movement Joints | 3
Movement joints: Provision of Brickwork Expansion Joints:
If a particularly demanding movement joint
occurs such as a joint being placed close to a
building corner a stronger de-bonded tie can
be used crossing the joint, but also providing
additional security.
DE-BONDED TIE
1
225
Mortar:
This advice assumes an M4 mortar similar to
a 1:1:6 Cement, lime, sand mix the normal
mortar designation for external walls. If a
stronger mortar is used for a parapet or free
standing wall designation M6 1:1/2:4 to 4.5 the
movement joints should be at closer than
recommended
centres.
If
traditional
construction is used with a full brick wall;
215mm wide in conjunction with lime mortar
movement joints could be increased but only
with the advice of an expert in mortar who
also understands the structure of the building.
Movement Joints:
Most of the movement which occurs in
brickwork is due to thermal expansion. While
moisture does have an impact as its smaller,
difficult to predict and, is generally
disregarded. There are two kinds of thermal
expansion. Reversible thermal expansion
which is accommodated by the movement
joint expanding and contracting. There is also
irreversible thermal expansion, which is
permanent.
The UK climate assumes a 60 deg C range: the
following advice is correct for the UK climate.
The designer should allow 1.3mm per linear run
of brickwork for the provision of movement
joints. This means for a joint at 7m centres the
joint should be 10mm wide. For a joint at 12m
centres the dimension should be 16mm wide.
4 | BDA Guide on the use of Movement Joints
225
Mortar should never be stronger than
necessary, a weaker mortar will tolerate more
movement than a stronger mortar. An over
strong mortar, considered elsewhere, does also
have an adverse effect in the provision of
movement joints, which may have to be at
closer centres than advised.
While an experienced practitioner may after
considering the geometry of the facade
slightly stretch the distances for North
elevations which will have less thermal gain,
the advice should be strictly observed for
South and West Elevations. If movement joints
are placed at closer centres or at greater
frequency no harm will occur.
There are three ways to design the provision
of movement joints, which if badly positioned
can be scars on the face of the building. Firstly,
you can either hide the joints behind other
elements or hide the joints in corners.
Secondly, the joints can be disguised by
considering the bonding; for example,
designing a straight joint as part of the bond
pattern. Thirdly, the joints may be emphasised
and be part of the rhythm of a building with
repeated elements.
Movement joints: Provision of Brickwork Expansion Joints:
Successful joint design
West Hampstead Railway Station
Sugar Mills, Edinburgh
Reused bricks will need the provision of the
movement joints because not only do they
require provision against expansion which
may occur. There is also some elements of
movement joints that may be required to act
University of London, Bloomsbury
against the differential movement of other
building materials. Reused bricks may have
also been under compression carrying
substantial loads. Release of weight may
allow expansion to take place.
University of London, Bloomsbury
BDA Guide on the use of Movement Joints | 5
Movement joints: Provision of Brickwork Expansion Joints:
Movement Joint Positioning:
Standard construction.
The general principles outlined apply both to
both horizontal and vertical joints, and in
general terms they can be considered to be
broadly similar. The rules for horizontal joints
for vertical compression are slightly more
onerous as many supporting frame materials
compress or shrink over time.
Horizontal MJ required
H
eevery 9m. (Compression of
sstructure may require more
3m
frequent MJ).
Above 9m to 12m MJ can
be accommodated by wall
b
ties in sliding connectors
3m
Sliding ties not
recommended above 12m
generally unless
calculated
c
9m
Break elevations into rectilinear areas
Vertical dimensions
for horizontal MJ
The general principle is to break the elevation
into rectilinear areas. Irregular or L shaped
brickwork is to be avoided.
Movement joints cannot pass through
structural members such as beans and lintels
although they may be routed around the end
WhileMJ’s
MJ’s cannot
cannot pass
pass through
While
structural
members
if shelf
through structural members
angles are used they can be
if shelf angles are used they
stopped to allow MJ.
can
be stopped to allow MJ.
The window jamb can
The
thenwindow
be usedjamb can
then be used
of a lintel both in the horizontal and vertical
plane. Movement joints must be continuous
unless terminating in a slip planes such as the
DPC. It is quite possible for movement joint to
pass through a shelf angle and for the shelf
angle to be stopped and started say 20mm
apart to allow the movement joint to pass
between the supporting steelwork.
London School of Economics
7m
7m
MJ’s do not need to be
continuous if the geometry allows
6 | BDA Guide on the use of Movement Joints
Movement joints: Provision of Brickwork Expansion Joints:
Modern brickwork is generally used in a single
skin facade. Single skin are supported on shelf
angles not of great height. More failures occur
at the top of the wall than lower down where
brick is under load. Parapets which have small
loads upon it are particularly prone to have
failures due to inadequate movement joint
provision.
Most building materials such as timber,
reinforced concrete, and steel will both expand
and contract in response to thermal changes in
temperature. While all materials will move in
response alterations in temperature changes
brick is amongst the very few materials which
actually have permanent and irreversible
expansion. The advice contained below will set
out deemed to satisfy provisions.
g p
A small building up to
to 10M
sq not
does
not
10m
sq does
require
any
MJ’s
require any MJ’s
Alternatively, bricks may be calculated on their
irreversible thermal characteristics which may
enable movement joints to be put in at greater
distances than the advice contained below.
This calculation is normally carried out by the
structural engineer conscious of the rest of the
buildings requirements.
There are some exceptions to the general
requirement of always having to provide
movement joints. Internal walls do not
generally require the provision of movement
joints. Buildings of a square or nearly square
nature of less than 10 M in either direction or
plan form do not generally require the
provision of movement joints as the forces are
opposite and equal.
W
MJ’s can be to
changes
of angle
changes
of angle
MJ’s to less than 1m
than
1m
10m
10m
Canbe
Can
twinned
twin for
symmetry
10m
m
sym
wall/building
MJMJtotowall/building
junction
junction
l When placing movement joints in a
building, there are a few simple rules that
must be understood which are not
common sense
MJ hidden
hidden
MJ
in corner
in corner
ELEVATION ELEVATION
Potential MJ positions
Potential MJ positions
6m
6m
6m
6m
Maximum
MJ
Maximum MJ
to corner
corner
to
Example (A)
Example
(A)
l One does not have to look at corners as
providing the end of the wall the plan
form of the building must be opened out
as if the corners didn’t exist
l One starts placing movement joints from
one area on the wall normally in plan with
reference to the elevation and follows the
building round until one arrives back at
the original point
2m
2m
8m
8m
Example
(B)
Example (B)
l Do not take any account of the corners or
changes of direction of the building into
account when working at the provision of
movement joints
BDA Guide on the use of Movement Joints | 7
Movement joints: Provision of Brickwork Expansion Joints:
Movement advice is contained within PD6697
clause 6.2.6 entitled Movement in Masonry. There
are two ways to design for movement in Masonry.
The provision of movement joints is not just
about the distance of linear runs of brickwork
but, also to do with the following factors listed
below. For most bricks, the general industry
advice of 1.33mm per linear metre run of
brickwork should be followed. This advice is
deemed to satisfy and a designer can rely on this
as being a sale failsafe option. For a maximum
distance between movement joints in straight
run of brickwork 12m this means one would have
movement joint of 16mm wide. For this reason
many designers choose to put movement joints
in at between 7 and 8m allowing for a 10 meter
movement joint.
At the parapet level movement joints are installed
at 6m centres, this is also true of freestanding
walls. Within a single wall movement joints may
be at 12m for the general run of the wall and 6m
for the parapet. The separating DPC required
under cavity tray for typical parapet will act as a
slip plane allowing the wall to accommodate two
separate areas of movement.
Damp proof membranes are often incorrectly
placed. The DPC is placed on a full bed of mortar
minimum of 6mm thick. The DPC should be of
the type that has good adhesion with mortar.
The next layer of mortar above is also a full bed
MJ
MJ
1m
1m
of mortar the DPC is sandwiched between two
beds of mortar. It is not possible to put a bed
joint unless the mortar joint is a minimum of
13mm wide. The DPC thereby acts as a slip play
allowing the wall to move differently in different
positions. The DPC should protrude slightly from
the finished a joint, so that the visible effects of
the DPC are seen. If the DPC does not protrude
the evidence of it cannot be seen water will drain
past the DPC into the masonry below.
In the event of a soldier course of bricks or
coping or capping of typical brickwork which is
not recommended because of poor weathering
characteristics the movement joints should be
placed at 3m centres. The provision of a separate
series of movement joints to copings and
cappings is accomplished by using a DPC as slip
plane.
Movement joints should be positioned in the
return angle of a short return. According to PD
6697 movement joints should be placed in any
return which is less than 675mm. The Industry
advice is that movement joints must be placed in
short returns of less than 1m. It is in these areas
where the movement differing movement of
foundations and cracking to masonry is likely.
The provision of movement joints in short returns
is a very good place to hide movement joints. For
returns greater than 1m the wall has enough
flexibility to allow flexing in the connecting wall
to take place.
MJ
MJ
Returns less than 1m require MJ
M Joint can be in either plane
MJ’sififaacorner
cornerjoint
joint
22 MJ’s
is
is not
notpossible
possible
2m
2m
2m
2m
SHORT RETURNS
8 | BDA Guide on the use of Movement Joints
Returns
Returnsgreater
greater
than
than 1m
1m can
canflex
flex
Movement joints: Provision of Brickwork Expansion Joints:
movement joints in larger commercial
buildings is to place them in the jam of the
window. The movement joint can then carried
on down to the spandrels panel in brickwork
and therefore minimised.
Movement joints can also be hidden behind
other features for example behind Rainwater
downpipes, or at the junction with other
materials such as timber or other materials. A
typical way of disguising the provision of
12m
12m
6m
6m
3m
3m
3m
3m
Brick coping
DPC acts as slip plane
Parapet
DPC acts as slip plane
Wall
Maximum distance between MJ
movement joints also have to be placed, to
take stress off the facade of the building.
Narrow vertical columns joining a junction of
horizontal brickwork can impart considerable
stress to the junction. Cracking may occur in
the corners unless there is a provision for
expansion provided. Similarly, if one has a large
opening with a smaller opening above the
stresses imposed on the facade could lead to
cracking. The general principle to be adopted
is of the facade to be broken up by the
provision of openings and movement joints
into rectilinear not L-shaped areas of masonry
which can lead to problems.
MJ
TheJambs
Jambsofofwindows
windows can
can be
be used
The
used for
for
expansion.
If
no
oversailing
lintel
is
used
expansion. If no oversailing lintel is used
Large openings require MJ’s
to release pressure
BDA Guide on the use of Movement Joints | 9
Movement joints: Provision of Brickwork Expansion Joints:
Movement joints have to be placed under walls
which are dissimilar in height as the walls will
move differently. If a movement joint is not
possible for design reasons 3 rows of bed joint
reinforcement should be installed in the bed
joints below to give tensile strength to the
brick work carrying variable loads. This
principle should be generally adopted to also
spread point loads.
MJ or BJR to junction
Bed Joint Reinforcement is one solution to
brickwork which can break many of the rules
listed above, and solve many problems. Bed
joint reinforcement is two of strips of stainless
steel wire joined at intervals by cross wires it
has a similarity to a model railway track. The
wire is often oval in shape compressed down
to around 3mm and 60mm wide. Joint
Ancon: Bed Joint Reinforcement
10 | BDA Guide on the use of Movement Joints
reinforcement is therefore hidden within the
depths of the bed joint and should be there for
the lifetime of the building. It should not be
confused with lightweight mesh which serves
no purpose. BJR is not expensive but does add
a cost to the wall for both labour and materials.
BJR gives a simple masonry wall a tensile
strength
adding
to
its
compressive
characteristics.
Movement joints: Provision of Brickwork Expansion Joints:
Bed joint reinforcement is used to build a stack
bonded wall which would otherwise be
unstable. Normally installed at 225 centres in
the bedjoint or every 3rd course in standard
brickwork it enables brickwork to achieve
unusual designs effectively.
School of Slavonic and East European Studies
One of the most beneficial effects of
reinforcement is that if installed at 225mm
centres in the bedjoint, movement joints may
be increased to 17m from 12m. While this is not
included in any standard this has been industry
advice for over 20 years with no apparent
failures. Additionally the Movement joints at
the termination of the run may then be 10mm
as opposed to 22mm.
Apart from a slight increase in cost reinforcement has
no drawbacks in use in masonry and its use is generally
recommended to avoid problems which might
otherwise occur.
Glyndebourne
Most designers will have noticed that many
buildings break the rules listed above. Ignoring
the rules may lead to failure and whilst
brickwork is forgiving the advice for MJ
provision should generally be followed. The
designer is therefore advised to follow the
advice contained within PD 6697 or this set of
advice which in most if not all circumstances
will guarantee there will be no issue with the
provision of movement joints.
Glyndebourne and School of Slovonic and East
European Studies shows heavyweight masonry and
lime mortar. Both buildings achieved a masonry
elevation with no movement joints, this required
particular structural engineering expertise.
BDA Guide on the use of Movement Joints | 11
Relevant British Standards
1.
2.
3.
4.
5.
6.
7.
8.
9.
BS EN 771-1:2011 Specification for masonry units part 1: Clay
Masonry Units
PD 6697:2010 Recommendations for the design of masonry
structures to BS EN 1996-1-1 and BS EN 1996-2
BS 8221-1:2012 Code of practice for cleaning and surface repair
of buildings
BS 7533-9:2010 Pavements constructed with Clay natural stone or
concrete pavers
PAS 70:2003 HD clay bricks guide to appearance and site measured
dimensions and tolerance
BS EN 15804:2012 Sustainability of construction works
BS 8103-2:2012 Structural design of low rise buildings
BS 8000-3:2008 Workmanship on building sites
BS EN 1344:2003 Clay pavers – requirements and test methods
10. National Federation of Demolition Contractors: (NFDC). Demolition of
refurbishment information data sheet 13. Nfdc-drids.com/sheet 13
11. BS EN 772-3:1998 Methods of test for masonry units determination of
net volume
12. BS EN 772-1:2011 Methods of test determination of compressive
strength
13. BS EN 1998-1.1:2005 and A1 2012: Design of masonry structures
14. BS EN 998-2:2010 Specification for mortar and masonry
15. BS EN 772-5:2001 Methods of test for masonry units’ determination
of the active soluble salts
16. BS EN 772-7:1998 Methods of test of masonry units. Determination
of water absorption of clay masonry damp proof courses
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