This document provides information on mortars used for brick wall construction. It discusses the typical materials in mortar mixes including sand, cement, water and additives. It describes requirements for good mortar such as workability and strength. Different types of cement and sand are outlined. Guidelines for mixing mortar by hand or machine and transporting pre-mixed mortar are also provided.

1. Occ20 Build Brick Walling
Mortars

2. Tutor Copy

3. Below are some web sites that may be useful
for students studying construction:-
• www.ibstock.co.uk Bricks and related sites.
• www.bca.ogr.uk British Cement Association
• www.buildingdesign.co.uk Building design services
• www.igltd.co.uk IG steel lintels.
• www.catnic.co.uk Catnic lintels.
• www.constuction-index.com Manufacturers
• www.mortar.org.uk Mortar industry association.
• www.insulation-installers.co.uk Directory and related links.
• www.trada.co.uk Timber research
• www.tra.org.uk Timber trussed rafter
• www.hse.gov.uk Health & Safety Executive.
• www.ucatt.org.uk Union of Construction Allied Trades & Technicians.
• www.cskills.org.uk ConstructionSkills.
• www.sheffield.gov.uk Planning application
information.
• www.ebuild.co.uk Self-build / land for sale etc.

4. Mortar

5. Characteristics of Materials
General purpose mortar can consist of:
• Sand.
• Ordinary Portland cement.
• Water.
• Plasticiser.
• Retarder.
• Accelerator.
• Pigments or colouring agents.

6. Requirements of a Mortar Mix
• The main requirement of a good mortar mix is
workability.
• Bricklayers require a mortar mix which is
described as ‘fatty’. This means it hangs on the
• trowel without being sticky, it spreads easily and
it does not stiffen too quickly or too slowly.
• The mortar should meet other requirements to
ensure that it retains its strength and
• durability during the life of the brickwork or block
work.

7. These requirements include:
• Adequate compressive strength.
• Adequate bond strength between mortar and bricks.
• Durability – resistance to frost and chemical attack.
• Joints sealed against wind-driven rain.
• An attractive appearance.
• The ability of the mortar to meet these requirements will
depend upon:-
• The materials specified for the mix.
• The workmanship of the bricklayer.
• The protection of the materials and brickwork against
adverse weather.

8. SAND
Used to create the ‘bulk’ for mortar. There are two main
types of sand used for construction purposes.
WASHED BUILDING Sand (FOR MORTARS)
Pure, clean sand – has had all impurities ‘washed out’ :
e.g. soils / silts / clays etc.
GRIT Sand
Larger grain sand – used in the production of concrete
works.
SILVER sand very fine sand – used for brushing into the
joints on block paving.

9. Sand used for mortars should
pass through a 5mm sieve.
• Poorly graded sands, with single-size
aggregates, contain a greater volume of air, and
will
• require a greater amount of binding agent to fill
in the spaces between each grain and make
• the mortar workable. Mortar made from poorly
graded sand will be weaker and is more
• likely to shrink, leaving cracks into which rain
can penetrate.

10. ALWAYS USE GOOD GRADED
SAND

11. The Silt Test for Sand
• To carry out the test, a 250ml measuring cylinder should
preferably be used.
• Fill the cylinder approximately up to the 50ml mark with a
salt/water solution (one teaspoonful of salt to 750ml of
water).
• Pour in the sand until the level is up to the 100ml mark.
• Add more salt solution until it reaches the 150ml level.
• Shake the mixture well.
• Stand the cylinder on a level surface and tap it until the
top of the sand is level.
• Leave the cylinder to stand for three hours.
• Measure the volume of the silt layer, and the volume of
sand.

12. To calculate the percentage silt
content, the following formula is
used:

13. SPECIAL CEMENTS
• As previously discussed cement is mostly made from
Limestone, Shale and Gypsum. It is used as the ‘binding
agent’ in mortars and concrete.
• The most widely used cement was developed in 1824 by
John Aspdin, using a limestone called Portland Stone.
This commonly used cement is known as Ordinary
Portland (O.P.) cement.
• O.P. cement is mainly used for concrete mixes but may
be used for bricklaying. If used for bricklaying, to make
the mortar more workable, it would require you to add a
………………………………………
• Over the years the development of cement has created
different types, for different purposes.

14. Types Available
• MASONRY cement
• O.P. cement with a Plasticiser or an Air-entraining Agent included.
Produces a ‘fatty’ mortar with high workability suitable for brickwork,
blockwork, stonework and rendering.
• SULPHATE RESISTING cement
• Sulphates are corrosive elements found naturally in the ground.
Sulphate crystals can enter walls below ground, or walls retaining
ground and attack O.P. cement. This attack takes the form of
causing the cement to expand causing cracking and splitting of the
masonry.
• RAPID HARDENING cement
• Chemical additives make this type of cement set and harden in half
the time of O.P. cement.

15. • PORTLAND BLAST FURNACE cement
• Finely ground O.P. cement and granulated blast furnace slag
(waste). Slower rate of setting than O.P. cement therefore not
generating the same amount of heat. Useful for very thick concrete
walls, slabs or mass-filled foundations. Greater resistance to heat,
seawater and acids.
• HIGH ALUMINA cement
• Made from Chalk and Bauxite – black in colour. Develops high
strength in 24 hours. Great heat produced during hardening which
can seriously affect its strength. Must be sprayed with water for 24
hours. Ideal for ‘emergency work’.
• WHITE cement
• Special selection of ingredients – used in the manufacture of pre-
cast concrete products, reconstructed stone, renderings and for the
production of cement paints.
• COLOURED cements
• By mixing chemically inert pigments with white or O.P. cement.
Cement strength slightly reduced, so compensate by adding an
extra 10% to the mix.

16. MORTAR ADDITIVES
• As previously discussed there are PLASTICISERS and
AIR-ENTRAINING AGENTS produced in either liquid or
powder form.
• Lime can also used for this purpose, but as mentioned
earlier, lime is a very hazardous material to work with.
• Bricklaying sand can be purchased with a desired
amount of lime already added. It is crucial that this type
of sand is kept covered from rain at all times.
• ACCELERATORS
• Added to a mortar mix to speed up the setting
process. Ideal for work in cold climates.
• RETARDERS
• Opposite to Accelerators – slow down the setting
process. Used in pre-mixed mortars.

17. • WATERPROOFERS
• Chemical (liquid or powder) added to mortar.
Used in rendering or work below ground.
• ANTI-FREEZERS
• Supposedly allows mortars to be used when
temperatures fall close to freezing.
• COLOURING PIGMENTS / AGENTS
• To colour mortar – in powder form - very
expensive – tends to ‘bleach’ over time –needs
care when ‘batching’.
• NOTE: All additives can weaken mortars.
Should not be used below ground level.

18. Mix Proportions
• The crudest method is gauging
the materials by the shovel-full.
The amount on the shovel can
vary according to the material,
e.g. shovels of sand are often
greater than shovels of
aggregate.

19. A slightly more accurate method is to use
a bucket to measure the materials. As
each bucket full is the same size, it will
have the same volume.

20. Volume mixing by hand using a
gauge box

21. Dry-Silo Mortar System
• The modern equivalent of the traditional weight
batching mixer is the dry-silo mortar system that
is becoming very popular. The system involves
the delivery of a large stand-alone silo that is
charged with the correctly constituted mix
materials in a dry state.
• The correct amount of water for a mix is
automatically measured and added each time by
a trained operator.

22. Machine mixing
• In general terms, this should be between
two and three minutes.
• On no account should the mix be allowed
to stay in the machine longer because the
materials will start to segregate.

23. Hand mixing
• This should take as long as required to ensure
that all the particles have been completely
integrated together. A high degree of agitation is
required when hand-mixing, to ensure that any
added plasticiser etc has the necessary effect.
• Mixed mortar should never be ‘retempered’ or
‘knocked up’ with added water because this
dilutes the cement/lime element of the mortar
which will result in a weaker mix.

24. Typical Mortar Mixes
• Mortar is a mixture of the following
materials in different combinations:
• Sand, cement and water.
• Sand, lime and water.
• Sand, lime, cement and water.
• Sand, cement, plasticiser and water.

25. • In site practice terms, it is possibly the
least understood and most abused
material on the building site.
• The design strength of the mortar should
be determined mainly by the strength of
the brick or block to be bedded on it. The
mortar strength should roughly match that
of the brick or block and in no case
should it be stronger than it.

26. Design of Mortar Mixes

27. Pre-mixed Mortars
Advantages
• No space required for the mixer and storage of materials.
• Less transportation plant and smaller labour force required.
• Quality control of the materials is the responsibility of the ready-mix
supplier.
• Economic for medium volume requirements.
• Consistency of colouring is easier to achieve.
Disadvantages
• Part loads are uneconomical, so the system may not be suitable for
small works.
• Waiting time for delivery may cause delays.
• More expensive than site mixing, so it is important to order the correct
amount to avoid wastage.
• If the mortar is supplied by site mixing methods it can be delayed or
halted to compensate for any delays due to inclement weather,
whereas mortar supplied pre-mixed may not have this flexibility.

28. Mixing Mortar by Hand on Site
• Using a shovel, repeatedly turn the ingredients into a pile
making sure that all the materials are thoroughly mixed
together.
• Form a hole or indentation in the middle of the pile of dry
mix.
• Add water to the mix. The amount of water should be
approx. 0.6 of the weight of cement (see water cement
ratios).
• The materials are mixed with the water from the middle
until all the water has been incorporated into the mix.
• The materials are then turned repeatedly until the mix is a
fatty workable mass.
• The mix is now ready for use.• Adding more water to the
mix will make the mortar easier to lay but it will reduce
the strength by up to 30%.

29. Mixing Mortar by Hand on Site

30. Mixing Mortar Using Mechanical
Mixers on Site
• Mixers can be powered by:
• • Petrol.
• • Diesel.
• • Electricity.

31. Procedure for mixing using
mechanical mixers
• Set up the mixer according to the manufacturer’s
instructions, or those of the site supervisor.
• Ensure that the correct power supply is available.
• Ensure sufficient materials and equipment are available.
• Carry out all safety checks and start mixer.
• Add the required water.
• Add the pre-gauged materials, adding the sand content
first.
• Add more water if required.
• Allow the materials to mix thoroughly for approximately
three minutes; never longer as segregation may occur.
• Turn out the mixed materials into a container or
wheelbarrow.
• When work is complete, clean out the mixer.

32. Water/cement ratio
• The strength of mortar can be affected by
the ratio of the weight of water in the mix
to the weight of the cement.
• Water/cement ratio = Weight of water in
the mix
• Weight of cement in the mix

33. • If a mortar mix has 50kg of cement, and
the total water does not exceed 25 litres
• (1 litre = 1kg), the ratio will be:
• 25kg Divided by 50kg
• = 0.5

34. Example:
• If the ratio of a mix is specified as 0.45,
then the quantity of water required for
each 25kg bag of cement added to the
mix will be:
25 x 0.45 = 11.25 litres (11.25kg)

35. EFFLORESCENCE
• Sometimes, especially new brickwork, can be
seen to have a white ‘fur’ / dust deposit on
the face. This unsightly effect is known as
Efflorescence.
• It is caused by ‘mineral salts’ trapped in the
materials used to make the brick / block etc.
• Whilst the bricks are dry these ‘salts’ are inert
but when water strikes the wall they can dissolve
and cause the staining. Eventually these salts
will completely dissolve but the effect on new
walling can be very disturbing.

36. • Even though efflorescence has no
damaging effect to a structure it may deter
prospective buyers.
• Not all bricks contain these salts so it is
imperative that whilst bricks are stacked
on site they are kept from contact with the
ground as salts in the ground could enter
the bricks.
• Efflorescence can also appear on the
mortar joints. This could be caused by
the sand initially containing impurities
or poor site storage of sand

38. WORK IN COLD WEATHER
• Building materials are quite capable of withstanding
effects from bad weather and low temperatures. It is
usually a poor design fault that causes materials to fail
e.g. walls being constantly wet.
• If materials are constantly saturated their pore
structures are virtually filled with water. When water
freezes it attempts to expand and if the materials are
unable to resist the stresses they will break down.
(SPALLING)
• This effect is known as Frost Damage.
• Building materials should be kept as dry as possible,
before use, and after construction.

39. • Mortars are particularly vulnerable
(contain water in the mix), before they
have set, as once frozen they will be
unable to set. The mortar will be
permanently damaged
• Bricklaying should be stopped when a
falling air temperature reaches 3
degrees Celsius

40. Remember
• WALLS DRY – cover with a waterproof
sheet – polythene can create dampness
underneath – think about the wind?
• WALLS WARM – cover with HESSIAN
sheeting – use insulation slabs.
• SAND DRY & WARM – keep covered –
store inside if possible – use hot air
blowers.

41. JOINTING & POINTING
When bricks have been laid to form a wall,
the surplus mortar is scraped flush with
surface of the brick face. This type of
surface finish is called
Flush Finish.

42. Why Point
• The main purpose of any joint finishing is to
improve the wall’s resistance to rain or the
ingress of water through the joint, as well as
enhancing the appearance of the wall.
• This is achieved by packing mortar into the
joints so that it has close contact with surface of
the brickwork.
• Jointing up brickwork is a critical part of building
face work, and it should not be hurried.

43. • One of the most important aspects of jointing up
brickwork is to avoid smudging or staining the
surface of the bricks.
• Timing is probably the most important aspect of
jointing up. The correct time to joint-up will be
determined by the suction rate of the bricks
being used and the weather conditions when the
bricks were laid.
• The consistency of the mortar is also crucial as
to when pointing takes place. If the mortar is too
wet, the joint will not be crisp and the mortar
may be dragged out from between the bricks.

44. JOINTING
• The term used for ‘finishing off’ mortar
joints, of the brickwork, before the
mortar hardens. (as the work proceeds)

45. Profiles of Mortar Joints

46. Keyed / Half round

47. Raked or square-recessed

48. Weather struck

50. POINTING
• Cutting out and pointing back at a later
date

52. TO RE-POINT AN EXISTING
PROPERTY
• Carefully remove old mortar, to a depth of
10mm, trying not to damage the surrounding
bricks.
• The old mortar must be removed ‘squarely’
off all the brick arrisess.
• Use a sharp plugging chisel or hand grinder.
• Wear the appropriate P.P.E. and consider
other people.
• Remove all traces of old or loose mortar and
brush joints well, to remove dust. Work from
the top, downwards.

53. • Mix mortar to specified mix and
workability. ( 1:4 )
• Use a fine water spray to dampen joints
for a small area (0.5 square metres)
• Using pointing trowel and hawk, force
mortar fully into joints and neatly finish
off.
• Protect pointing from weather, until set.