| DESIGN,
CONSTRUCTION AND PERFORMANCE |
| This section offers
general advice on -the use and performance of Colinwell Bricks.
The text should be read in conjunction with the advisory
publications referred to. Construction work should follow the
recommendations of BS 5628: Part 3; 1985 and those of the
appropriate design and specification authority. All Colinwell
Bricks comply with BS 6073: 1981. They are fully loadbearing, the
minimum Class 3 type exceeding 20.5 N/mm² compressive strength. |
Durability
Use below dpc |
| All bricks except
lightweight are suitable for use below dpc in the outer leaf of
cavity walls in normal ground conditions. |
Durability in sulphate conditions |
| Colinwell bricks are
manufactured utilising either Ordinary Portland, or Sulphate
Resisting cement. The use of Sulphate Resisting cement is normally
restricted to Commons and Engineering Quality bricks and only to
special order.
The degree of sulphate resistance
in aggressive ground conditions is dictated by the cement type and
cement content of the mix. It should be noted that under certain
circumstances to a certain extent Blast Furnace cement will provide
a similar degree of resistance to Sulphate Resisting cement.
|
Durability in sewerage systems |
| Engineering Quality
bricks have been specifically designed for use in manholes,
inspection chambers and in other areas of foul water such as those
resulting from domestic sewerage. They are not suitable where
industrial effluents or concentrations of acid are present. The
application of Engineering Quality bricks is covered under BS 5628
Part 3 |
Ground Conditions & Recommended Brick |
 |
Groundwork |
| For footings,
groundwork below dpc and for other areas of general loadbearing
brickwork Colinwell manufacture a common brick and engineering
brick to various compressive strengths. |
Freestanding Walls |
| Freestanding and
boundary walls should be built strictly in accordance with the
engineer's or specifier's instructions. Consideration should be
given to the effects of rain and frost and in particular to the
effects of high wind pressures.
Freestanding walls should
normally be designed without reliance on flexural tensile bond
between mortar and brick. However, if the design is based on
flexural tensile bond, attention should be given to the mortar
adhesion (see BS 5628: Part 3:1985 Clauses 17.5 and 32.3). Where
there are no piers or returns at the ends of wall panels adequate
restraint should be provided by means of suitable metal ties.
The thickness of freestanding
walls and the size of any piers depend on the height, location and
exposure of the wall and on its layout e.g. whether straight or
staggered.
Design guides and tables are
available and may be used in conjunction with advice from a
structural engineer or other appropriately qualified person.
Mortars of designation (iii) -
1:1:6 Cement: Lime: Sand (or equivalent) mix should be used for
freestanding walls and the joints finished as the work proceeds.
Unless the design has been based
on the 'No Tension' method, the dpc provided at the base of the
wall should only be of either two courses of slates, fully bedded
and half-lapped, or of a proprietary type of dpc which can resist
flexure. (See also BS 5628: Part 3: Clause 18.4.1)
|
Earth Retaining Walls |
| In addition to the
above guidance, two additional factors should be considered in the
construction of earth retaining walls:
(i) the loads acting on the wall
from the retained material.
(ii) the use of a suitable brick and mortar to resist possible
attack from sulphate soils or groundwater. Consideration can also
be given to the application of a waterproofing treatment.
Fourteen days should be allowed
from completion of the wall before backfilling. Refer to BS 5628:
Part 3: 1985 Table 13 (K) for further information.
|
Parapet Walls |
| Exposure conditions
must be taken into account in the selection of bricks, in making
provision for movement and in making preventative measures against
rainwater penetration. Further guidance on these aspects is given
in BS 5628: Part 3: Clauses 20.3.2, 21.5.7, Figure 12 (g) and
Tables 13 (F) and (G). |
Copings, Cappings and Sills |
| Freestanding walls
and parapet walls, other than those in sheltered locations, will
benefit from the provision of copings (i.e. units which have a
drip throating and which overhang sufficiently to shed rainwater
clear of the exposed face of the brickwork below - for further
details see BS 5642: Part 2:1983).
Where brick-on-edge is used
either as a coping in conjunction with creasing tiles, or on its
own as a capping or as a sill, Class 3 Colinwell Bricks may be
used for sheltered locations. A Class 4 or Class 5 brick will give
added protection and should be used for more exposed conditions.
Mortars in such constructions
should be designation (ii) a 1 : ½ : 4 Cement : Lime: Sand (or
equivalent) mix.
|
 |
|
Below copings and
cappings, except where creasing tiles are used, and below sills, a
flexible type dpc should normally be used. The dpc should project
at least 1Omm from the face of the brickwork and should be fully
bedded between mortar on both top and underside.
For further
guidance refer to BS 5628: Part 3: 1985, Clause 21.7 and Table 13
(I), and to BS 5642: Part 2: 1983.
|
 |
Slip Bricks |
| Colinwell can supply
brick slip bricks to match the full range of facings produced and
guidance for their use can be found in BS 5628: Part 3:1985:
Clauses 27.3 and 32.12
Generally, mortar alone is not
adequate for fixing slip bricks. A proprietary adhesive should be
used, following the manufacturer's instructions.
Fixing surfaces should be cleared
of all dust and provision made for any background movement.
|
Chimmeys, Flues and Fireplaces |
When appropriately
rendered or used with flue linings, Colinwell bricks can be
satisfactorily used for chimneys and flues. They are also suitable
for fireplaces, again in conjunction with appropriate liners of
firebricks and in such a way that no direct flame or heat can
affect the bricks.
Construction of chimneys and flues should be in accordance with
Approved Documents A and J of the Building Regulations and
reference made to BS 5628: Part 3:1985 Clause 197, 21.5.8. and
Table 13 (H). |
Wall Ties |
| Ties should be spaced
as directed in BS 5628: Part 3:1985 Table 9 (A) and placed in the
mortar as laid, not pushed into the mortar joint. They should be
level, or sloped down towards the external leaf and cleared of
mortar droppings or other residue. |
 |
| Additional ties are
needed for brickwork adjacent to openings.
Ties of the double triangle type
or of proprietary stainless steel thin strip may be suitable, but
the use of rigid ties, which preclude differential longitudinal
movement in the two leaves, should be avoided.
In accordance with Approved
Document E of the Building Regulations, ties used for cavity party
walls should be of the wire butterfly type.
|
Fixings |
| Fixings designed for
brickwork can be used with Colinwell Bricks, but not those made
for use in pre-cast or in situ concrete.
Colinwell Bricks are easily and
neatly penetrated with masonry drills or plugging tools and they
can be chased simply and accurately with appropriate tools.
|
Movement Provision |
| In common with most
building materials Colinwell Bricks are subject to movement and
provision should be made for this in the design and construction
of walls. In general, vertical movement joints should be provided
at intervals of 7.5 to 9.0 metres with the spacing of the first
joint from a return normally half this distance.
The position of such joints
should be such that the ratio of the length to the height of the
resultant wall panels does not exceed 3:1.
|
 |
| Joints can either be
made as a feature of the design or be concealed behind downpipes
or similar features.
The use of such joints and
the placing of bed-joint reinforcement above and below openings
will help accommodate movement from all sources associated with
the structure.
|
 |
| Where stability
considerations require continuity across a movement joint, dowels
should be used, ideally of flat metal strip, 20Omm x 25mm x
3mm thick. These should be placed across the joint approximately
every sixth course in the mortar bed, and set parallel to the
plane of the wall. One end of the dowel should be debonded, i.e.
wrapped in polythene, building paper or similar. Proprietary types
of dowel, with one end sleeved, are also available. The use of
such dowels, with plain ends, permits movement within the length
of a wall whilst preventing any movement at right angles.. |
 |
| Detailed guidance
will be found in BS 5628: Part 3: 1985 Clause 20 |
Lintels |
| Unless doors or
window frames are specifically designed to carry brickwork
suitable concrete or metal lintels should be used. Bearings should
not normally be less than 15Omm each end and should bear onto full
brick units. Lintels should be of appropriate specification and
have adequate bearings to suit the span and loading involved. Long
spans or exceptional loads may require the use of padstones.
Consideration should be given to the accommodation of movement,
and to the use of a slip plane where differing materials meet or
are bonded together. For further guidance refer to BS 5628: Part
3: 1985 Clause 19.3
Appropriate measures should be
taken to prevent the passage of rainwater in lintel areas.
Detailed advice will be found in BS 5628: Part 3:1985 Clauses
21.5.5, 33.4 and Figures 12 (d) and (e).
|
Resistance and Durability |
| The physical
properties of Colinwell Bricks offer a high degree of resistance
to harmful attack from climatic and most other sources of damage
and contamination.
Colinwell's carefully controlled
methods of production ensure the consistency of these properties
and provides the brick with inherent durability.
|
Rainwater |
| The water resistance
of a building material is related to its porous structure.
Colinwell Facing Brick is densely packed with minute pores, a most
effective barrier against ingress of moisture. |
Effloresence |
| Colinwell Facing
Bricks are not affected by the disfiguring problems caused by
efflorescence or "lime bloom". The density and low water
absorption of Colinwell Brick and the low soluble salt content of
the materials used in the manufacture of Colinwell Facing Brick
ensure the elimination of this problem. |
Frost |
| The fine composition
of Colinwell Bricks, which inhibits water penetration, minimises
the risk of frost damage and spalling. In this it compares more
favourably than clay brick- Colinwell Bricks' resistance to frost
drainage has been proved in extensive freeze / thaw laboratory
testing and has been demonstrated by their durability in long
established building projects. |
Coastal Environment |
| Occasional wetting by
sea spray will not normally have a harmful effect on Colinwell
Bricks. No special treatment is necessary but attention should be
paid to the mortar used. |
Chloride |
| Colinwell Bricks will
not normally suffer from the occasional splashing by chlorinated
water, nor from the atmosphere of swimming pools. Brickwork
courses adjacent to pool surrounds and walkways should be
protected with a suitable surface treatment. |
Organic Growths |
| The appearance of
algae or other growths on external walls is due to the effects of
long term saturation by rain, damp soils, adjacent vegetation or
by animal contamination.
Internally it is normally a sign
of dampness.
Should algae appear on bricks
before they have been used it should be cleaned off or the bricks
discarded, otherwise the adhesion between bricks and mortar will
be impaired.
However, subsequent growths on
established brickwork are not usually damaging. Their removal will
probably be decided for cosmetic reasons, which are more
likely to be important in urban rather than rural environments.
|
Acids |
Colinwell Bricks
should not be exposed to splashing or impregnation by concentrated
acids, or be used in situations subject to strong acidic fumes.
Such effects can cause erosion or disfigurement of the brick and
will affect the colour.
Please contact our technical department for advice before using
proprietary acid based brick cleaners. |
Pollution |
| Colinwell Bricks are
unlikely to suffer from normal atmospheric pollution, the
composition and closed surface of the brick offering resistance to
the effects of pollution. However, if they are affected the
surface of Colinwell Bricks is readily cleaned using recommended
methods.
NOTE: Durability is related to
strength. Whilst Class 3 (20.5 N/mm²) bricks offer the durability
detailed in the foregoing, higher strength Classes should always
be considered for extreme conditions or exposed situations i.e.
Class 4 (27.5 N/mm²) Class 5 (34.5 N/mm²).
|
|
Protection |
| As the brickwork
proceeds guard against stains and blemishes. Any which do occur
should be removed immediately as it is not always possible to do
so in a subsequent cleaning operation.
Keep completed facework covered
to protect it from abrasion, splashing and by the mortar leaching
effects of the rain.
To prevent dirt contamination in
windy or rainy conditions turn scaffold boards away from brickwork
when not in use.
Cover partly finished and
completed brickwork until mortar has set, using polythene or
similar sheeting. Such protection is especially important against
the detrimental effects of saturation and frost. Refer to BRE
Defect Action Sheet (Site) No. 64.
|
Mortars |
| It is important that
the mortar should suit the bricks used. in general, the hardened
mortar should be weaker than the bricks.
In accordance with BS 5628: Part
3: 1985, Table 13 (C1 and E) for work above d.p.c. level,
designation (iv) mortar mixes can be used (e.g. 1:2:9, cement:
lime:sand). They are preferable provided masonry is protected
during construction from saturation and freezing and that
structural or other considerations do not require a stronger mix.
Where freezing may occur during construction and for below d.p.c.,
boundary walls, parapets and chimneys, a 1:1:6 mortar is
preferable.
For below d.p.c. applications
where sulphates are present in the groundwater the use of sulphate
resisting cement for the mortar may be necessary, see BS 5628:
Part 3: 1985, Clause 22.4. A 1:½:4½ mortar should be used for
sills, copings and earth-retaining walls.
Air entrained mortars are more
resistant to damage by freezing, although, in general, cement /
lime / sand mortar are preterred. Lime based mortars have several
advantages over other types of mortar of similar compressive
strength:
• Improved workability.
• Higher water retentivity, which resists suction from brick and
so maintains the exceptional workability.
• Autogenous healing. Cracks in the drying mortar are healed by
interaction between rain water, lime and air.
• Stronger bond between mortar and bricks.
• Increased resistance to rain penetration.
* Tests carried out by the Mortar
Producers Association on various combinations of bricks and
mortars showed that limelsand mortars, used in concrete brickwork
resisted rain penetration more efficiently than the clay brickwork
tested.
Equivalent mixes using a mortar
plasticiser or masonry cement may be used in accordance with the
manufacturer's instructions. Detailed recommendations relating to
mortar mixes for specific situations, including such equivalent
mixes are given in BS 5628: Part 3 1985, Table 15 (see below).
BS 5628: Part 1:1978 advises
"wet, ready mixed retarded cement: lime: sand mixes should
only be used with the written permission of the designer".
(C1. 15.2)
Information should be obtained
from the Supplier or the Mortar Producers Association - their Data
Sheet No. 12 or leaflet "Ready To Use Mortar - A Guide For
Use On Site".
The use of a gauge box or other
accurate measuring device is essential to ensure uniformity of
finished appearance and stability of structure. A shovel should
not be used as a measure.
Apart from workability consistency of mixing is important in
achieving a good finished appearance. The ratio of mortar to brick
on the face of brick walls is significantly high, ranging from 17%
in stretcher bonds to 24% in other bonds. It is essential to use
uniformly mixed mortars to maintain consistency of colour.
Pronounced variations in mortar
shades can give the impression that different coloured bricks have
been used.
The use of admixtures for
resisting frost damage is not recommended. Adverse effects on the
hydration of the cement, or other undesirable results, could occur
(see BS 5628: Part 3:1985, Clause 23.3).
|
 |
Jointing and Pointing |
| The jointing of
brickwork serves several primary functions:
• Durability and rain
penetration resistance.
• Fire resistance.
• Overall appearance of the finished brickwork
• Stress distribution within the brickwork.
• Protecting mortar from risk of frost attack.
The following points should be
observed when forming joints.
• Maintain a regular 10mm
thickness of joints.
• A bucket handle type of joint is recommended unless otherwise
specified. Raked or recessed joints can increase the risk of rain
penetration - see Table 11B, BS 5628: Part 3.
• To keep the cavity clean strike off joints within the cavity
as work proceeds.
There is differing opinion as to
the respective merits of finishing the joint as work proceeds or
raking and pointing. Finishing as the work proceeds may provide
better frost resistance but the consistency of mortar mixes must
be carefully controlled if uniformity of colour in large wall
areas is to be maintained.
Raking, where adopted, should be
to a depth of approx. 18mm and the joint then formed with fresh
mortar.
Raking and pointing must be
carefully carried out to avoid damange to the brickwork
|
types of joint
 |
Bad Weather Conditions |
| Where bad weather
conditions are anticipated immediately before, during or
immediately after bricklaying, adequate precautions should be
taken. For further guidance see BRE Defect Action Sheet No. 64. |
Energy Conservation |
| Approved document L
(LI Conservation of Fuel and Power: 1990 Edition) gives two
methods of ensuring compliance with the Regulations: (i) Elemental
Approach, (ii) Calculation Method (2 Procedures) but emphasises
that requirements may be met in other ways. Following the guidance
in LI will be taken as tending to show compliance with the
regulations in the event of alleged contravention. This deals with
the Elemental Approach only. |
Main Provisions |
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