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Wienerberger - Frequently Asked Questions

Click on the drop down links below to read a frequently asked question:

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Most Frequently Asked Questions: General

Are your facing bricks suitable for use at ground level?

Yes. All extruded wirecut, stock and traditional handmade facing bricks are of guaranteed durability, of category F2 (European Standard EN 771-1:2003) and FL designation (British Standard 3921:1985).

Are special shaped bricks available?

Yes. In addition to British Standard (4729) shapes we also manufacture an extensive range of purpose-made specials to match our standard product range.

What about information on mortar colours?

We can provide both complementary and contrasting colour references for our products.

Do your bricks suffer from efflorescence?

All Terca products have low soluble salts content as defined in EN771-1 (category S2) and BS 3921 (category Low) and do not suffer from abnormal characteristics. Good site practice of protecting bricks in storage and during construction will minimise the potential effect. For further detailed information on the mechanism of efflorescence, please refer to our Guidance Note: Efflorescence and Staining of Brickwork.

Why are 'handed' special shaped units required?

Left and right hand versions of certain specials are sometimes needed because of the shape of fittings for detailing. Even with simple standard units, handing may be required to maintain a consistent direction of texture in alternate courses.

What specials are normally held in stock?

Popular specials including angles, canted, bullnose and plinth units in Smooth Red and other mainline finishes are available ex. stock. We also offer a competitive delivery period for all other specials including purpose-made units.

What design advice do you offer?

Our Design Services Department offers free advice on the suitability of our products for specific applications. We also provide guidance on constructional details when drawings are submitted for projects where Terca bricks have been specified.

Do you offer CPD Seminars?

A number of presentations are available on specific topics including technical properties of bricks, site workmanship, and special shaped bricks. One particular seminar package, combining aspects of these three main areas, achieved CPD certification, and the department would be pleased to arrange a presentation at a suitable venue. For more details please contact our Cheadle office.

Frequently Asked Questions: Clay Tiles

My clay tiles appear to have a sprayed on finish. Why is this and will this weather off?

The beauty of Natural Red clay tiles lies in the way in which they retain the natural colour of the clay material, whilst maturing to a darker, richer shade. Colours such as Flanders, Tuscan and Antique are created by applying an 'Engobe' to the surface of the tile prior to firing in the kiln. This is a ceramic material, as is the tile itself. Therefore when the tile is fired the engobe and the tile 'fuse' together and become one. This means that the surface colours of the tiles are permanent will not fade under any circumstances and the slow change that does take place will be a steady darkening of the red colour.

It should be noted that Wienerberger's Sandtoft brand surface-coated clay tiles easily pass the European Frost Resistance test, BS EN 539-2: 1998, with no damage to the tile or its surface.

My clay tiles have small white-centred chips on their surface. What is causing this and will it affect the durability of the tiles.

The small pits that are occasionally visible on the surface of clay products are created when pockets of lime immediately below the surface expand, causing the surface above the lime to be pushed up or 'blown'. This expansion takes place as soon as the tiles leave the kiln as the tiles absorb moisture from the atmosphere. Lime occurs naturally in most clays and can usually be neutralised, ie prevented from expanding, by submerging the tiles in water.

Wienerberger's Sandtoft brand make every effort to prevent lime blows, although occasionally the process can still occur before the tiles have been fully soaked. The expansion action of the lime only occurs immediately after the tiles leave the kiln. The process stops once the tiles have absorbed moisture and can not re-occur. Therefore there is no risk of further 'pitting' to the tile surface after the tiles have been laid on the roof. It is a common misconception that clay products can be attacked by frost action due to irregularities within the surface finish. But there is no possibility that the small pits, or 'lime blows', will affect the future durability of the tiles.

All our clay tiles pass the European Standard test for frost resistance, BS EN 539-2: 1998. Under the terms of the European Standard for clay roofing tiles, BS EN 1304: 1998, small pits or chips 7 mm or less in size in the surface of the tiles are not regarded as faults.

My new clay pantile roof looks wonderful but I am concerned about the gaps between the tiles. Will my roof leak?

A. Clay pantiles have been around for about 400 years now and have long proved themselves to be an extremely efficient form of roof covering. In early methods of clay production there was very little control during firing over the final shape of a product. This meant that the design of a roof tile was such that it had to be weathertight whatever its final shape - the shape of a traditional pantile is a wonderful testimony to early roof tile designers. Not only do they keep the water out but the gaps around the tiles minimise the suction effect of the wind, helping to prevent wind damage. Because modern clay tiles are pressed, rather than extruded in the way that concrete tiles are, far more weatherproofing features, such as top interlocks and weather barriers, can be designed into the surface of the tiles.

Frequently Asked Questions: Concrete tiles

A white 'bloom' has appeared on my concrete roofing tiles. What is it, and will it harm the tiles?

Efflorescence is a naturally occurring phenomenon caused by water in the form of rain, condensation or dew penetrating into the pores of the concrete and dissolving lime. The solution diffuses to the surface of the product, the water then evaporates and leaves behind a white film of lime. The lime naturally occurs in the cement which is used in the manufacture of all concrete products. Since the lime content of the concrete can vary and the weather conditions obviously differ, the level of efflorescence can also fluctuate considerably.

The same chemical process which brings the lime to the surface of a tile carries on, enabling it to be degraded and washed away by the rain, so that eventually the efflorescence disappears by itself - usually in a matter of months. Once the lime has disappeared from the surface of the tiles it rarely re-occurs. Unlike some manufacturers, Sandtoft treat the surface of all their concrete tiles with acrylic polymer coatings to not only minimise the formation of efflorescence, but to give stronger and longer lasting colours If efflorescence does appear, it has no detrimental effect on the long-term performance of the tile.

My roofer has laid Calderdale Concrete Slates on my roof 'straight bonded'. As all the photos and other roofs I have seen have the tiles laid 'broken-bonded', will I have problems with my roof?

Although it is recommended that Calderdale Slates are laid 'broken bond', this is mainly for aesthetic purposes - they are a flat tile emulating the appearance of a double lapped slate. But as Calderdale Slates are a single lapped, interlocking tile there is no technical reason why they cannot be laid 'straight bond' in the same way as other single lapped tiles such as, for example, Double Roman tiles. However, it should be noted that all Sandtoft specifications for Calderdale Slates are based on the tiles being laid broken bond. Also, technical data such as the minimum recommended roof pitch are based on wind-driven rain testing carried out on tiling arrays laid broken bond.

My concrete tiles have a painted finish. Why is this and will it weather off?

A. All concrete tiles are coloured to give them the appropriate appearance. Unlike clay tiles this colour will eventually fade away over time. However Wienerberger, unlike some other concrete tile manufacturers, colour the tile body, the tile surface and then add an acrylic coating, which gives the Sandtoft tiles the following benefits: -

  • Enhances the intensity of the tile colours Prolongs the effective life of the cement/pigment rich tile surface
  • Minimises water loss during the curing stage to allow improved concrete strengths
  • Protects the surface from rain water erosion and corrosion (acid rain)
  • Minimises dust and dirt and inhibits lichen/moss contamination
  • Minimises the risk of surface salts and efflorescence formation during the critical early life of the product
  • Ensures colour between product batches and main tiles and fittings always match
  • Reduces the effect of the scuffing which occurs during handling and transportation
  • Increases rain and snow dissipation rate from the roof Reduces surface water capillarity, ie improved performance

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