FAQ

A burnt clay facebrick type product is resistant to petrol and diesel. For many years Caltex specified only clay pavers for their garage forecourts for this reason (Tarmac was never used as petrol and diesel attack it) Although petrol can stain bricks, they are easy to clean.

Acid-resistant clay tanks are common in industry and these will also cope best with petrol and diesel. We would suggest a specialized mortar and possibly a lining is used. There are many specialist suppliers – just search the net!

The acid and chemical-resistant clay bricks are featured products in various construction and refractory applications and are available in various shapes and types such as Arch Bricks, Tapper Bricks, Sleeves, Tongue & Groove Bricks.

Chemical-resistant clay bricks are used in the following application areas:

• • Chemical plants: Dyes, Intermediates, Acids and Alkalies
    Fertilizer Plants
  • Thermal power plants for chimney construction
  • Petrochemicals and refineries
    Pharmaceuticals etc
  • Galvanizing Plants

Preparation

• • Plan site layout e.g. position of building, material stores, access etc.
  • Store and protect all materials to minimise saturation and contamination.
  • Control the wetting of bricks in hot, windy weather.
  • Do not lay surface saturated bricks.
  • Set out at ground level to locate all openings before commencing bricklaying.
  • Lay out dry and minimise broken bonds.
  • Prepare and take care of gauge rods – they are important quality control equipment.
  • Work all levels from one datum.

Protection of brickwork
The best treatment is to prevent it from getting dirty in the first place – so protect the wall as work progresses from mortar droppings. After the first course of bricks has been laid – protect the base of the wall by laying sand, straw, sawdust or plastic sheeting along the ground. This minimises mud splashes and damage from mortar droppings.
As clay brickwork should be kept dry as possible during construction, cover the walls at the end of each day’s work and during rain in order to keep brickwork free from mortar stains.

At the end of each working day clean the toe boards closest to the wall and turn the boards back to prevent rainfall from splashing mortar and dirt onto the brickwork.

Process & Techniques

• • Mix small batches of mortar to suit building rate and 20-minute initial set timing.
  • Bed all DPC’s on fresh mortar
  • Blend face bricks from a number of packs to minimise colour bonding.
  • Plumb, level and square brickwork
  • Fill all mortar joints solidly to minimise water penetration.
  • Clean mortar dropping from cavities regularly

As with all cleaning procedures a rinsing operation should be carried out shortly after application, and care is taken to dispose of run-off solutions safely.

If the above method is not successful with coloured mortars, specialist advice from the coloured mortar supplier should be sought.
On the rare occasions when a vanadium efflorescence is present, hydrochloric acid-based cleaners must not come into contact with the efflorescence, otherwise, a dark stain will result which will become fixed on the surface.

As with all cleaning procedures a rinsing operation should be carried out shortly after application, and care is taken to dispose of run-off solutions safely.

If the above method is not successful with coloured mortars, specialist advice from the coloured mortar supplier should be sought.
On the rare occasions when a vanadium efflorescence is present, hydrochloric acid-based cleaners must not come into contact with the efflorescence, otherwise a dark stain will result which will become fixed on the surface.

In the making of firebrick, fireclay is fired in the kiln until it is partly vitrified, and for special purposes may also be glazed.

High-grade fire clays can withstand temperatures of 1775 °C (3227 °F), but to be referred to as a “fire clay” the material must withstand a minimum temperature of 1,515 °C (2,759 °F). Therefore Fire bricks are not needed in braai or fireplaces – a good quality FBX brick will be more than sufficient for the bed of the fireplace, while a standard FBA or NFP brick is sufficient for the sides.

The “nibs” technically are only to assist with laying and are not for any structural reason. Most nibs are offset so as not to end up contacting each other, but strictly speaking, the jointing material is designed to diffuse the lateral and vertical forces by transferring them through to the bedding sand and sub-bases layers.

It is highly recommended that the grade of jointing material is different to the bedding sand, to expand in the joints and create the lockup. It must also be vibrated so that it fills the joint to the bottom and in so doing allow the forces to be transferred through. Again, one of the more important issues in the design is the edge restraint which holds the whole system together, and patterns relevant to the usage are also critica

When ordering or specifying clay bricks, ensure the following points are discussed and made known to the suppliers:

• • Expected sizes. Not all bricks are manufactured to the standard imperial size of 222mm long x 106mm wide x 73mm high
  • The required application e.g. type of building, finish etc.
  • The degree of exposure to weather conditions, closeness to the seas etc.
  • The track record of the preferred brick in the area where you are building
  • An undertaking or warranty from the brick supplier that the bricks delivered will be fit for purpose
  • Colour expectations in the case of face bricks or exposed brick areas
  • The acceptable levels of breakage during delivery to site
  • The brick manufacturer registered with the Clay Brick Association of SA

To avoid colour banding it is highly recommended that face bricks are taken from a number of different packs and carefully blended during building operations.

• • Properties that require consideration when buying or specifying clay brick are:
  • Compressive strength (varies from 7MPa to 50MPa)
  • Water absorption (face brick up to 10%, NFP up to 16%)
  • Modulus of rupture – strength in bending
  • Moisture expansion – is important when detailing long walls
  • Initial rate of absorption: This affects the development of the bond between the mortar and the brick. Bricks with high rates of absorption (often lower quality) may require pre-wetting well before laying to prevent absorbing excess water from the mortar mix. Trial and error experiments when bricks arrive on site will determine the need to pre-wet bricks.

Please refer to our Technical guides under `SALT ZONES` and salt erosion of clay bricks. If you have a property situated on the beachfront there is usually some degree of deterioration taking place! All bricks are porous and will absorb salt, and many factors are at play so it is impossible to say how long it will be before deterioration of the façade begins. The softer lime mortar used in external brickwork prior to the 1960s can be substantially affected by salt deterioration. This is more prevalent in the exposed location but buildings located 2-3 kilometres from the sea can also be affected. The mortar becomes soft and powdery. More recent Calcium Silicate face bricks can still suffer from surface delamination. This occurs as the salt crystals adhere to the brickwork and is absorbed into the bricks. During rain, the crystals will expand and then push the outer surface of the brickwork away. Once the hardened surface of the brickwork is lost, then the rate of deterioration of brickwork will accelerate. It is not possible to prevent the surface delamination of bricks.

Remove large deposits with wooden implements to avoid damaging the paver surface. Following the pre-wetting of the area, treat the residue of mortar by careful application of a dilute hydrochloric acid solution or a proprietary cleaning solution. The application of the acid breaks down the cementitious components but is not damaging to clay pavers. As with all cleaning procedures a rinsing operation should be carried out shortly after  application, and care taken to dispose of run off solutions safely. If the above method is not successful with coloured mortars, specialist advice from the coloured mortar supplier should be sought. On the rare occasions when a vanadium efflorescence is present, hydrochloric acid based cleaners must not come into contact with the efflorescence, otherwise a dark stain will result which will become fixed on the surface.

Firstly, what is Brickforce? Brickforce is a British brand consisting of two main parallel wires joined by in-line welded cross wires. Main wires are manufactured to a flattened profile to simplify location into the mortar joint without steel build-up problems at lap positions corners/junctions or when used in conjunction with wall ties. There are various other materials that can be used for brick reinforcement, e.g. Mild steel reinforcing rods and expanded metal. These products and others suitable as brick reinforcement are obtainable in rolls of varying lengths and widths, from your local hardware shop or builder supplies merchants. Why use masonry reinforcement? Masonry has excellent compessive qualities and the majority of buildings constructed using this material last for many years with little maintenance. However, masonry has no significant tensile strength, and movement caused by substrata changes, moisture or thermal effects can cause cracking. The use of masonry reinforcement is a very simple and cost-effective way of greatly enhancing the strength and durability of masonry construction

A burnt clay facebrick type product is resistant to petrol and diesel. For many years Caltex specified only clay pavers for their garage forecourts for this reason (Tarmac was never used as petrol and diesel attack it) Although petrol can stain bricks, they are easy to clean. Acid-resistant clay tanks are common in the industry and these will also cope best with petrol and diesel. We would suggest a specialized mortar and possibly a lining is used. There are many specialist suppliers – just search the net! The acid and chemical-resistant clay bricks are featured products in various construction and refractory applications and are available in various shapes and types such as Arch Bricks, Tapper Bricks, Sleeves, Tongue & Groove Bricks. Chemical resistant clay bricks are used in the following application areas: Chemical plants: Dyes, Intermediates, Acids, and Alkalies Fertilizer Plants, Thermal power plants for chimney construction, Petrochemicals and refineries, Pharmaceuticals, etc Galvanizing Plants

Are you planning a major project? Our user-friendly guide “Bricklaying made Easy” is available at Builders Warehouse, or from the CBA for just R150. Preparation Plan site layout e.g. position of the building, material stores, access, etc. Store and protect all materials to minimise saturation and contamination. Control the wetting of bricks in hot, windy weather. Do not lay surface saturated bricks. Set out at ground level to locate all openings before commencing bricklaying. Lay out dry and minimise broken bonds. Prepare and take care of gauge rods – they are important quality control equipment. Work all levels from one datum. Protection of brickwork The best treatment is to prevent it from getting dirty in the first place – so protect the wall as work progresses from mortar droppings. After the first course of bricks has been laid – protect the base of the wall by laying sand, straw, sawdust, or plastic sheeting along the ground. This minimizes mud splashes and damage from mortar droppings. As clay brickwork should be kept dry as possible during construction.

To avoid confusion and to standardize, the following terminology was introduced and is currently used by the industry.

FBS – FACE BRICK STANDARD.

Clay bricks that are selected or produced for their durability and uniformity of size and shape.

NFP – NON-FACING PLASTERED.

Clay bricks are suitable for general building work that is to be plastered

FBX – FACE BRICK EXTRA. Clay bricks that are selected or produced for their durability and a high degree of uniformity of size, shape, and colour

NFX – NON-FACING EXTRA.

Clay bricks are suitable for use, plastered or unplastered, for general building work where durability rather than aesthetics is the key selection criteria: below damp-proof course or under damp conditions, or below ground level

FBA – FACE BRICK AESTHETIC.

Clay bricks that are selected or produced for their durability and aesthetic effect derive from non-uniformity of size, shape, or colour.

…E – ENGINEERING UNITS.

Masonry units are produced for structural or load-bearing purposes in the face or non-face work, where the manufacturer supplies clay bricks to an agreed compressive strength.

The acceptable water absorption for clay bricks are between 12% and 20%. If you are using engineering bricks the closer you are to the 12% the better the result will be. When the water absorption is too low, i.e. below 12%, it may be difficult to obtain a proper bond between the mortar and the bricks. Handmade historic bricks; many of which are often found to have an average porosity value of around 35%. With highly porous bricks there is a danger that they might rapidly absorb moisture from the bedding mortar (particularly in warm weather) causing it to stiffen quickly. This would result in it losing the all-important characteristic of plasticity that would inhibit correct and accurate positioning to line and face-plane and the provision of a secure bedding, leading to poor adhesion with attendant negative consequences on aspects of compressive and flexural strengths of the overall walling.  It is important not to confuse ‘porosity’ with ‘permeability’, as they are not the same. Porosity is a measure of the available pore space within a brick. Permeability, however, is a measure of the extent to which air, water, or other fluid can pass…

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It is common to find growths such as algae, lichens, liverworts, and moss growing on hard surfaces. Contrary to popular belief, they do not damage what they are growing on, but can cause patios, drives, paths and steps to become slippery. Moss, lichens and algae should not grow on clay bricks unless the area is heavily shaded, is under trees, or is not laid to an adequate fall. If such growth does occur and is considered undesirable then the area should be treated with a proprietary moss killer used in accordance with the manufacturer’s instructions.Such products take some days to be effective and work best when applied during a spell of dry weather. Any thick growths should be scraped off first and the chemical treatment well brushed in. Some treatments leave a residue to discourage the re-growth of the moss and algae, but this will only be of limited value if the paving remains damp and in shade. Non-chemical control Dislodge moss from between paving by running a sharp knife along the cracks. Alternatively, use a block paving brush with a long handle, narrow head, and wire bristles for effective cleaning without stooping.

Firebricks (or refractory bricks) are totally over-specification in a domestic fireplace or braai. They are also expensive and not easily available. Refractory Bricks are normally rated from around 1600’C upwards – a braai will never reach this heat. Any clay face brick or semi-face (fired) brick can be used for a braai. Facebricks are fired to around 1000 – 1250’C to stabilise their structure, and they have a high thermal mass which helps them insulate for heat. The heat in the fireplace would need to be higher than this to have any effect on the brick. Concrete bricks or any regular concrete product made with Portland cement cannot stand up to high temperatures and will disintegrate at the temperatures required by a pizza oven or braai. With excessive heat, cement and mortar between the bricks can crumble. Build the outer skin of the sides of the braai/fireplace with a standard mortar mix (1 bag cement : 3 Barrows Sand) with brickforce and cavity ties. Build the inner skin with a well-burnt clay face brick (FBX) using a weaker mix (1 bag: 6 Barrows Sand) – this allows more joint movement and reduces cracking from heating.

Clay bricks expand fractionally after leaving the kiln (primarily due to moisture in the air) and minute increases in height and width (0.006 percent per annum) continue at a decreasing rate for up to 5 years.Fortunately with clay products the majority of this expansion happens almost immediately the product leaves the kiln and is exposed to atmosphere. Building walls without control joints that exhibit cracking, appeared to have expanded only 2mm to 4mm; In the good old days all the bricks would be purchased at the beginning of a project and stored for many months before being used. It was thought this gave them an opportunity to harden and “dry out”.  Today, purchases are JIT (just-in-time) and the timing from order email to delivery to use is less than a week. The age of bricks in stock will vary considerably from factory to factory and region. Obviously if product is in high demand they do not stand too long in the yard before delivery. There are many sources of movement in walling and paving including ambient moisture levels, temperature, loading and creep, chemical action, ground movement, and settlement.