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Our Skyline Box range of glazing bars offer an economical roof glazing solution when compared with curtain walling roofing systems. The glazing bar's strength is provided by an internal box section. The glazing bar is weathered by a screw on pressure cap (PC1) with a choice of plain (PC2) or ornate (PC3) cosmetic outer snap-on cappings to conceal all fixing screws.

When used with high performance double glazing units with warm edge spacer bars and argon gas filling this system can achieve an overall U Value of 1.4W/ m²K to comply with Building Regulation Document L.

Our Skyline range of glazing bars offer an economical roof glazing solution incorporating slim sightlines. The glazing bar's strength is provided by an internal stalk (or fin) which is cut away at the top and bottom main fixing positions.
An internal snap-on ornate capping system (PC4) is also available if desired to fully conceal the internal stalk giving the appearance of a feature timber rafter.

When used with high performance double glazing units with warm edge spacer bars and argon gas filling this system can achieve an overall U Value of 1.4W/ m²K to comply with Building Regulation Document L.

Timber rafters (supplied by the builder or joinery sub-contractor) will create an appealing visual effect inside any home and are totally protected from the effects of weathering by our externally clad Rafterline Patent Glazing system.
Due to the pleasing aesthetics of aluminium and timber materials our Rafterline system is the most popular specifiers choice for domestic projects.

When used with double glazing and thermal breaks this system is easily capable of providing an overall U Value of 1.6W/ m²K to comply with Building Regulation Document L.

Our Traditional patent glazing system remains our customers most popular choice for use on unheated spaces such as Railway Stations, glazed canopies and covered ways where thermal properties are not a consideration.
This system has been installed on thousands of projects nationwide and is available with a choice of capping systems to suit your needs.
A truly great glazing system combined with economy and a proven track record. 30,000m² of this glazing system has been installed by us on many major railway stations throughout the UK in recent times.

This system is capable of accommodating solid or multi-wall polycarbonate sheets or double glazed units up to 28mm thick if used on unheated spaces or where compliance with Building Regulations Document L are not a consideration.

Our 'Heritage' Patent Glazing Bar range is truly unique amongst roof glazing systems; there are no alternative products available on the market which can match an original lead covered steel patent glazing bar which originates from the Victorian era. This range has been manufactured by us unaltered for over a century and is the perfect product for listed buildings and for use in the refurbishment of significant and historic buildings. This system is also still very popular for new build projects and should not to be overlooked on today's modern buildings where a unique character look is desired.


Due to roof glazing being exposed to significantly higher levels of solar heat than vertical glazing consideration needs to be given to the possible thermal stresses created in glass which are capable of causing the glass to fracture. Toughened glass is not subject to fractures from thermal stresses. However, laminated and wired glass certainly are. Please read the following indepth information regarding thermal stresses and how best to avoid this occurrence in your roof glazing projects.


  • Thermal Safety in Glass Products
  • Factors Affecting Thermal Stress
  • Assessment of Thermal Safety

Figure 1. Hot centre and cold edge – the generation of thermal stress

Figure 2. A typical thermal fracture

This information introduces the concept of thermal stress which may be induced in glass as a result of exposure to solar radiation. It also gives an overview of the factors taken into account when assessing the thermal safety of glazing exposed to solar radiation and offers useful guidance on how to approach this aspect of building design. Thermal safety of glass must be taken into account early in the design of buildings, since it has implications for the specification of the glass.



The magnitude of thermal stress depends on the temperature difference between the hottest and coldest parts of the glass and also on the distribution of the temperature across the glass. Glass is commonly glazed by retaining the edges of the glass with a gasket or glazing bead. The area of glass exposed to solar radiation absorbs heat, rises in temperature and expands. The edges of the glass, which are shielded from solar radiation, remain cooler than the exposed area (see Figure 1). The resulting differential expansion causes tensile stress at the edge of the glass, if this exceeds the breakage strength of the glass a thermal fracture will result (see Figure 2).




Any factor which increases the hot centre/cold edge differential tends to increase the thermal stress. We have listed below in order of prevalence the main factors which can cause thermal fractures in glass used in overhead patent glazing systems. None of the causes listed below are associated with Toughned glass but Laminated and Wired glass as both highly susceptible to fractures if the following criteria exist on your project.

Internal shading below Laminated or Wired Glass (from blinds or other devices)
Blinds and other internal shading devices can interfere with the free movement of air over the glass. They also reflect and re-radiate solar radiation, increasing the temperature of the glass. We therefore insist that close fitting internal blinds should NEVER be installed below patent glazing when the inner pane is of a laminated or wired type as this will almost certainly cause the majority if not all panes to fracture. Toughened glass should always be used in these cases.

Solar Control Films applied to Laminated or Wired Glass
The application of solar control films to laminated or wired glass will significantly increase the absorption of the glass and hence the thermal stress resulting in fractures in most cases. We will NEVER supply laminated or wired glass with solar control films but retro-fitting of these items have been carried by others after our installation. The results are very costly. Only use solar control films on toughened glass.

Wide Back-up materials/builders kerbs at the bottom of Patent Glazing with Laminated or Wired Glass.
Any means by which heat is reflected or re-radiated back into the glass from inside the building increases the heat absorbed by the glass. The term back-up is used to describe a permanent structure close to the inside surface of the glass. It is usually associated with wide builders kerbs which are below the glazing creating a significantly higher temperature of the glass situated directly above the kerb. Laminated and Wired glass are very likely to fracture in these circumstances. Toughened glass is unaffected by this condition.

Internal heaters below Laminated or Wired Glass.
The primary source of energy that gives rise to thermal stressing is the sun. Secondary sources, such as convection or radiant heaters can supplement the solar heating and increase thermal stress, especially if the heat is directed onto the glass. Laminated and Wired glass will thermally fracture when located close to internal heaters. Always use toughened glass in these instances.

Glass edge condition
The condition of the edges of the pane of glass is extremely important. As the tensile stresses induced in the glass are located at the edges, the breakage strength of the glass is in the main related to the extent and position of flaws in the edge.

High absorption of solar radiant heat
The most important glass property in relation to thermal stress is absorption.The greater the absorption of solar radiant heat, the higher the resulting temperature of the glass will be and the greater the thermal stress.

External shading over Laminated or Wired Glass
Partial or prolonged shading can produce large temperature differences. Additional thermal stresses will be induced in the glass if it is partially shaded from the sun by external elements, such as canopies, deep transoms, balconies, deep mullions or adjacent walls. Shadows may also be cast by more distant objects such as trees or nearby buildings.




The thermal safety of glass is assessed by comparing a calculated value of the maximum temperature difference the glass will encounter in its glazed situation with the safe temperature difference for the glass. If the safe temperature difference exceeds the maximum temperature difference for a particular pane of glass, then that pane will be Thermally Safe for the proposed glazing situation.
The term Thermally Safe is defined in the context of probability of failure:
~ The risk of thermal stress fracture from a good, as-cut edge is sufficiently low to be acceptable
~ The assessment is only valid provided the conditions at the site match those taken into account in assessing the thermal safety

If the glass is not thermally safe, then consideration will need to be given to adjusting the system or the glass type. Toughened glass has a much greater safe temperature difference than annealed or laminated glasses and consequently the solution is often to change the glass specification to a toughened form of the selected glass.
Pilkington has developed a technique for predicting the thermal safety of glazed installations subjected to solar radiation. An assessment service is available for glasses based upon the client submitting a completed Thermal Safety Check form.