The external envelope of a building not only fulfils the primary function of protecting the interior from the elements, it also projects an image to the outside world. Whichever glazing system is used for the façade this section outlines the common design criteria needed for SOLAGLAS CONTRACTING to detail the installation:

  • structural stability
  • guarding
  • weather resistance properties
  • control of the internal environment

The key to the success of any glass facade installation project is the close collaboration between the designer and our technical team.

This teamwork brings together and balances aesthetic objectives with functional performance and quality in terms of:

  • thermal insulation
  • reduction in solar heat gain
  • light transmittance
  • sound reduction
  • weather resistance

ISO 9001 quality procedures give full control throughout the enquiry stage, the design process, glass processing,fabrication of the framing system, contract management and installation.

Design and function

SOLAGLAS CONTRACTING can help combine design and functional objectives through access to a comprehensive range of architectural glass, framing and glazing systems.

Facade systems available from SAINT-GOBAIN SOLAGLAS are:

  • bolted all-glass systems: structural glass assemblies, 
  • curtain walling
  • windows
  • framed and frameless ground floor glass screenwork

framed and frameless glass commercial doors The performance criterion of a façade are determined by:

  • the intended use and occupancy of the building, the nature of the interior environment, the safety of the occupants and the level of security required
  • forces acting on the façade: it must be designed to withstand wind-loading, to support its own weight, and it must be weather-resistant.

Balancing these criteria can lead to conflicts. Systems which provide ventilation and limit the intrusion of these elements, can be designed.

Design criteria

Façade systems incorporating glass are not designed to bear any structural loads of the building.

They must be strong enough however, to withstand:

  • wind loads
  • dead loads due to the self-weight of the installation
  • movement due to settlement or thermal expansion
  • Imposed loads produced by the intended use of the building
  • In certain circumstances loads associated with guarding

These need to be transferred to the building structure. Information about the vertical and horizontal spans to structural fixings and the nature of that structure is required to calculate the configuration of the system elements in order to provide strength and stability.


Even when the loads and consequent movement are applied, the glazing system needs to remain weather-resistant.

SOLAGLAS CONTRACTING will determine either the mullion and transom configurations for curtain walling, or the number of bolts and pane size for structural glass assemblies, provided all necessary criteria are supplied:

  • Full plans and elevations relevant to the works to be carried out
  • Design wind pressure and category

  • Position of available connections to structure
  • Glazing specification

It is the most adverse combination of wind load, span and weight that determine the strength requirement,the size and arrangement of support for an installation.

Structural stability

Wind loading

The design wind load, calculated according to BS 6399: Loading for buildings Part 2 Code of Practice for wind loads, is required from the specifier.The wind acts on a facade creating a variety of different forces through:

  • direct action
  • down draughts
  • vortices
  • separation
  • funnelling

When the wind meets a building in its path, it either slows down at the face of the building or deflects and accelerates around the sides:

  • at the face the wind slows down and kinetic energy is converted to pressure
  • where the wind is deflected over and around the building, the pressure is reduced and can become negative
  • behind the building, eddies are created causing a drop in pressure

The design wind load is derived from site wind speed. This may be taken from a map of the UK drawn by the Meteorological Office showing hourly mean wind speed at 10m above sea level. The site wind speed is then corrected for:

• altitude

• local topography
• seasonal exposure
• direction
• nature of surrounding terrain
• height of the building
• building shape and dimensions
The wind speed is converted to pressure using standard pressure coefficients from BS 6399: Part 2.
The wind pressure varies at each point of the surface of a building externally and internally, positive and negative.

The specific value of the pressure on each surface depends upon the angle at which the wind approaches, so the orientation needs to be known. The shape of the building, or slenderness ratio, the position of the installation and details of any features affecting the distribution of wind or snow also need to be considered.
Neighbouring buildings can affect wind pressure, so their proximity and height need careful consideration.
Pressure is exerted by the wind internally, depending on the position and size of openings connecting to the outside of the building, and the porosity of the envelope. Positive internal pressures will add to external suction forces acting on the cladding, as well as having an effect on internal elements.

The variance of pressure and wind patterns around a building, must be taken into account during design.

Not only does it affect the structure’s strength and stability, it affects rain and thus the weather-resistant properties of the installation.

Dead loads

Façade elements are not designed to take the building’s structural loads. They must support however, their own weight. (The sum of the glass and framing). SOLAGLAS CONTRACTING can calculate the glass thickness required for the application. The need to limit deflection in the glass so that it is not visually disturbing would also be taken into account.

  • in bolted systems the weight and wind loads are transferred via bolts and brackets to the building structural support
  • in a curtain walling system the dead loads and wind loads are transferred via the transom joint to the mullion. These loads are then transferred back to the building support structure through the mullion fixing points.

Building movement and imposed loads

Allowance must be made for the movement of the building structure due to settlement, different rates of expansion due to temperature changes and imposed loads induced by building usage.

Such information must be made available to ensure stability and weather-resistant properties are maintained.

Interface with the supporting and surrounding structure

Glass installations, such as bolted systems and curtain walling, support dead loads and resist wind loads, but these loads must be transferred back to the building’s structural frame via brackets and anchor points.

The system is normally located in front of the structural frame, generally concrete floor slabs or structural steel work. The set-off distance is the depth of the bolt and bracket in structural glass assemblies or the mullion depth in curtain walling.

The brackets and anchor points must themselves accommodate:

  • building movement
  • thermal movement
  • construction tolerances
  • self weight of the system
  • applied loads such as wind action

Anchors that tie the installation back to the building structure can be either cast in place, ie, positioned in the formwork before the concrete is cast, or post installed.

The choice of the fixing depends on:

  • In some cases suitable manifestation should be provided in accordance with BS 6262 : Part 4 and Document N. Large areas of transparent glazing can be found both internally and externally in commercial buildings.

    If the glass is not immediately obvious, due to the absence of substantial framing or fittings, it should be made apparent by some form of manifestation.

    The manifestation may take the form of decoration, solid or broken lines, patterns or company logos.

    It must be of a size to make it immediately noticeable and at an appropriate height between 600 and 1500mm above floor level.

    Manifestation should preferably be permanent. If applied materials are used they must be durable and not easily removed.
    The above information on guarding gives only general guidance. You must ensure that your design is suitable for the particular application and that it complies with all relevant local and national legislation, standards, codes of practice and other requirements.the material into which the fastener will be inserted

  • the load on the anchor
  • method of assembly
  • edge distance and grouping

SOLAGLAS CONTRACTING will select the appropriate fastening system. The correct selection and installation

of the fastener is dependent upon the loadings it is intended to take.

Structural fixings

The availability and nature of the structural support needs to be known. Although the vertical distances between structural fixings would normally be floors, larger vertical spans can be specified.

Details of the structure at the top of the façade and the cill will determine the nature of fixing. Structural steel work may be introduced to provide intermediate support if required.

Fixing points

The support and fixing of external façade cladding is covered by Building Regulations Approved Document A Section 2. It provides guidance regarding the support and fixing of external façade cladding which, by reason of weight or height, would present a hazard if it became detached from the building. Façade cladding will meet the requirement if:

• it is capable of safely sustaining and transmitting to the supporting structure of the building, all dead, imposed and wind loads

the cladding is securely fixed to and supported by the structure of the building. This fixing should comprise both vertical support and lateral restraint
• provision is made, where necessary, to accommodate differential movement of the cladding and the supporting structure of the building
• the cladding and fixings (including any support components) are of durable materials, the anticipated life of the fixings being not less than that of the cladding. Where the fixings are not readily accessible for inspection and maintenance, particular care is required in the choice of materials and standards of workmanship
• forces imposed on facade cladding by ladders or access cradles for maintenance should be derived from consideration of the equipment likely to be used.

Sloped and overhead glazing

A number of façades systems such as structural assemblies, curtain walling and patent glazing can be used in sloped and/or overhead situations. These could be linked to the full façade or used independently, such as in atria.

Glazing systems can also be used to cover passages and construct canopies providing pedestrian access with effective protection from the elements.

Overhead glazing helps achieve even distribution of light. Sloped glazing illuminates a greater surface area than the same window in the vertical plane.

As the depth to which light will penetrate into interior space is limited, a solution is to have a hollow heart to the building and create an atrium which allows light into the central area. The atrium can be in the centre of the building or complementing one or several glazed walls.

As the atrium increases in height it would have to be broader to allow light to reach the lower levels. Also on the lower levels the window lights would need to be larger to allow light into the interior spaces.

Sloped and overhead glazing presents several specific design and function issues. When specifying overhead glazing it is necessary to consider:

• wind, snow and maintenance loads

-Loadings are obtained from BS 6399: Part 2 for wind loads and BS 6399: Part 3 for imposed roof loads.

-The sloped glazing is subject to positive and negative wind pressures. In order to determine the configuration to give the system the required strength and stability it is necessary to calculate the pressure and suction values and use the greatest absolute value, bearing in mind that the fixing and anchor points need to bear the loads in both directions.

• risk of impacts from falling debris or snow from adjacent structures on to overhead glazing

SOLAGLAS recommends laminated glass for single glazed situations, and as the inner pane of sealed units in sloped overhead double-glazing. If it fractures, laminated glass will hold together and generally be retained in the frame.

Thermal insulation or U-values

U-values for glass and sealed units are calculated in accordance with BS EN 673 for vertical glazing.

Corrections are required for sloped overhead glazing.


Water flows over sloped overhead glazing to a greater degree than in vertical applications. It is imperative that water is drained to a suitable gutter and that systems are designed to drain water that may penetrate the outer seals of the glazing system.

If water collects on surfaces close to the horizontal, problems with sediment and long-term etching may arise. Curtain wall systems incorporate special transom caps to reduce the collection of water on the slope.

Opening lights

Opening lights provide natural ventilation and, where necessary, smoke ventilation compliant with BS 7346: Part 1. These lights can be mechanically or remotely operated.

They can also be linked to the building management system.

Glass as guarding

See “Technical Questions” . In certain circumstances attention should be paid to ‘Glass as Guarding’ as defined in Building Regulations approved Document K and BS 6180 Code of Practice for Barriers in and about Buildings, especially when the glass panels in curtain walling or structural glass assemblies span between floor slabs.

The use of glass as guarding in full height barriers

What is a guarding situation?

When the glazing protects a minimum change in level of 600mm in a domestic situation or 380mm in a non-domestic situation.

• Glazed barriers should be designed to BS 6180 unless another barrier, designed in accordance to BS 6180, is provided in front of the glass to protect the building user.

What type of glass should be used?

If the glass falls below the level of 800mm above finished floor level, (FFL), then it should be a safety glass in accordance with the safety glazing recommendations given in BS 6262 : Part 4, which will withstand the applied loads and provide containment, (Document K).

Glass barriers must withstand three design loads without breaking:

  • a horizontal uniform load or line load, (kN/m), pressure exerted on a horizontal line 1100mm above finished floor level
  • a uniformly distributed also known as ‘UDL’, (kN/m2), pressure exerted over the entire panel
  • a point load, (kN), concentrated

External barriers must also withstand appropriate wind loads.

What is a ‘full height barrier’?

Full height barriers may be formed partially or wholly from glass. They may, in fact, not be ‘full height’ at all.For more information, see “Technical Questions” 


In some cases suitable manifestation should be provided in accordance with BS 6262 : Part 4 and Document N. Large areas of transparent glazing can be found both internally and externally in commercial buildings.

If the glass is not immediately obvious, due to the absence of substantial framing or fittings, it should be made apparent by some form of manifestation.

The manifestation may take the form of decoration, solid or broken lines, patterns or company logos.

It must be of a size to make it immediately noticeable and at an appropriate height between 600 and 1500mm above floor level.

Manifestation should preferably be permanent. If applied materials are used they must be durable and not easily removed.

The above information on guarding gives only general guidance. You must ensure that your design is suitable for the particular application and that it complies with all relevant local and national legislation, standards, codes of practice and other requirements.


The weather-resistance of a façade is achieved in different ways:

-Single front sealed systems rely on weatherproof outer seals to the infill panel rebates to stop water penetration to the interior.

-Drained and ventilated systems have weatherproof outer and inner seals to the infill panel rebates to stop water penetration. The rebates and cavities are also drained and ventilated to the exterior to prevent the accumulation of any water that may bypass the outer seal.

-Pressure equalised systems are a refinement of the drained and ventilated system, but the ventilation openings are larger to allow rapid pressure equalisation in the cavities with the external pressure. It is important that the inner seals to the cavities are airtight and continuous to resist pressure fluctuations. It is also necessary to compartmentalise within cavities to prevent pressure loss across an elevation to zones exposed to lower wind pressures.

This is achieved by ensuring that:

• outer portions are sealed as tight as possible against rainwater ingress

• inner portions are sealed as tight as possible against airflow
• cavities are made into compartments
• each compartment is connected to

the exterior by protected openings.

Testing has shown that window and curtain walling systems can achieve better results using pressure equalising principles. However, pressure equalisation cannot counteract other forces such as gravity.

Good detailing and competent installation provided by SOLAGLAS CONTRACTING will ensure an all weather-resistant system. As well as determining the forces acting on the building, an understanding of the wind pattern reveals how water can ingress through joints.

Under a combination of forces water can be forced through potential weak points in a façade system:

  • vertical expansion joints
  • glass perimeter
  • gaps in gasket lengths
  • gasket corners
  • transom and mullion intersections
  • infill perimeter
  • frame mitre
  • window to wall joints, to the head,

the sides or to the cill. Careful design, detailing, fabrication and installation of the chosen system by SOLAGLAS CONTRACTING will help prevent water ingress.

Procedures through ISO 9001 ensure that any factors that may lead to water ingress are considered and resolved.

Gaskets and sealants
Joints with other parts of the structure will form a weather-resistant join and allow for differential movements due to heat, building settlement and live loads.
Gaskets limit air and water penetration whilst allowing relative movement due to heat expansion, and forces caused by wind pressure acting on the opening vents and deflections in the glass pane.

The gaskets also prevent the glass coming into contact with the frame. There are various shapes that display different characteristics when the forces act upon them.

Joints in the fabric of a building envelope are the inevitable consequence of the construction process and all building materials suffer dimensional changes during service.

All joint-sealing systems must be able:

  • to bridge between similar or different construction materials
  • to act as a barrier against environmental conditions
  • to accommodate thermal movements
  • to complement the appearance of the building façade For certain projects the sealant must provide a flush glazed façade, such as in structural glass assemblies.

Different types of sealant vary in their properties in terms of:

  • elasticity
  • movement accommodation
  • durability
  • interaction with other local materials

The correct sealant must therefore be specified for the application.

Controlling the internal environment

The glass panel is a key contributor to the internal environment. In the contemporary design brief, emphasis has moved towards environmental control and energy conservation, with recognition of glass’ contribution towards this whilst still providing the feeling of space.

The negative effects of cold, heat and noise can all be reduced by high performance glass and glazing. See “Double-glazed units” .


The glass infill panel predominantly determines thermal performance, but the frame may bridge this insulation. Unless the frame is thermally improved,condensation may occur as well as heat loss. The thermal insulation of a façade can be significantly increased by using a thermally improved frame, using one of three standard methods:

1. Resin:

A two part polyurethane resin is poured into a designated chamber in the aluminium profile. When set, the profile is machined to create a consistent break (nominally 6mm) between the inside and outside surfaces.

This operation is known as ‘De-bridging’. Due to the nature of production, the interior and exterior of frames employing this form of thermal improvement are the same colour.

2. Polyamide:

Two aluminium profiles are connected using Polyamide, (glass filled nylon 66) strips. These are rolled together to form a composite profile.

This allows the internal and external components to be of different colours, either painted or anodised.

3. EPDM (Ethylene Propylene Diene Terpolymer) or rubber gaskets:

Predominantly used for curtain walling, an integral thermal strip made from EPDM separates the internal box from the pressure plates and external cappings.

In its unbroken condition the frame itself has a thermal transmittance value of approximately 5.6 W/m2K. With the thermal improvement this is reduced to approximately 3.0 or

3.2 W/m2K. The total thermal transmittance of the facade is predominantly determined by the glass infill panel, where a high specification double-glazed unit can achieve 1.2 W/m2K. Other factors to consider are:

Solar control , thermal stress in glass and acoustic glazing .

Fabrication and installation

SOLAGLAS CONTRACTING offers a skilled and professional aluminium fabrication operation, providing nationwide coverage from ISO 9001 accredited manufacturing sites.

Mullions and transoms are square cut from sections of aluminium alloy 6063 T6 and conform to BS 1474.

Surface finishes

Powder coating paint consists of a polyester resin, which gives durability, a pigment for colouring and a carrier in order for it to be applied.

After being cleaned the aluminium is electrostatically charged and the powder applied. The powder paint is then heat cured.

Normal powder coatings that are applied are 40 µm thick. However, where specified in aggressive environments such as swimming pools or heavy industrial chemical production areas, 60 µm is recommended. In shoreline installations modified powder coatings may be specified to provide greater protection.

Swatches for standard colour options are available on request. Non-standard colours to match RAL references, or metallic finishes, are also available.

Anodised finishes are available where a film of near uniform thickness results from an electrolytic process in which the immersed aluminium is the anode or positive element. Immersing the aluminium in boiling water afterwards fills any pores; the oxide combines with the water to produce a hydroxide, which seals each pore.

The required thickness of the film depends upon the environment in which the aluminium will be situated and is determined from BS 1615. 25 µm is a normal thickness.

For more information, contact SOLAGLAS CONTRACTING.

Curtain walling

Curtain walling is a non-load bearing cladding system located in front of the structure to form an integral part of the building envelope.

Although its prime purpose is to create a weatherproof barrier, it can be designed and fabricated to introduce individuality to the building’s aesthetic appeal.

While curtain walling is usually characterised by a square or rectangular grid of mullions and transoms, other shapes, such as trapezoids and triangles, can be incorporated in the design. The specification of the glass and use of opening ventilators introduces comfort and light to the internal environment.

High and low rise façades can be created and the designs can be further enhanced with faceted curves, sloped roofs and canopies including ridges, hips and valleys, also pyramids and lantern lights. A façade of curtain walling can incorporate inserts such as tilt and turn, top swing, pivot windows and side hung windows.

Concealed vents, either top hung or tilt and turn, as well as commercial doors to suit the requirements of the project, can also be incorporated.

Design criteria

The design challenge is to create the image but keep stability and weather-resistant properties while withstanding:

• wind loads
• dead loads due to the self-weight of the installation
• building movement
• imposed loads produced by the intended use of the building
• in certain applications loads associated with guarding.
SOLAGLAS CONTRACTING will calculate the required mullion and transom size for each project provided all necessary criteria are supplied, including:
• full plans and elevations relevant to the works to be carried out

• design wind pressure and category
• position of available connections to structure
• glazing specification.

Mullions and transoms

The mullions supply the support to a curtain wall screen and the configuration of the box section determines their strength.

The depth of the box and/or the addition of internal reinforcing gives a variety of ways to add strength.
For a given wind load the strength required for the mullion depends on the span between fixing points and the weight of glazing it is required to support.

At no time should a curtain wall mullion be used as a structural member within the building, or have loads designed for the primary structure transferred to the curtain wall grid.

The selection of transom is calculated from the wind load, weight of the infill panel and the span.

Attention should also be paid to the maximum allowable loading that the transoms are able to carry.

Although the depth of the mullion and transom may vary between 20 to 200mm, the sight width for a given system remains the same.

Mullions and transoms are 45, 52 and 64mm across the face depending on the application and the specific system adopted.

Whilst the vertical distances between structural fixings would normally be floors, larger spans can be specified subject to calculation. Within the grid size, the introduction of intermediate transoms and mullions lead to a variety of design options for vision and non-vision areas.

The infill glass panels must be chosen so as to withstand the stress caused by wind pressure. The correct choice depends on pane size, dimensions, method of support and wind load.

Sensible design will also take into account the need to limit deflection in the glass so as not to be visually disturbing. Generally, the larger the span between structural fixings, the greater the wind load and the greater the panel weight, the deeper the mullion and transom will be. As each project presents different sets of circumstances, it is difficult to give typical sizes.

Depending on the configuration of the primary structure, the curtain wall is either hung or propped.

Building tolerances and movement

Building tolerances must be allowed for as the structural opening and fixing areas may not always be plumb, square and true dimensionally.

Thus when designing a curtain wall screen consideration must be given to allow for tolerances within the building make-up.

During a building’s life-span the fixing points and openings may be subject to movement which must also be taken into account during the design stages of the curtain wall screen.

Maximum and minimum dimensions for tolerances and movement must be ascertained and agreed during the pre-contract design stage. At no time should a mullion member be fixed rigid at all fixing points to structure.

Slotted holes in the brackets at the anchor points allow for movement between the curtain wall and the structure. Expansion joints can be incorporated to join two mullions to allow for the vertical movement of the aluminium.

Longitudinal movements for a short run of curtain wall may be accommodated at the wall junction, but for long runs intermediate expansion joints on the transom must be formed.


SOLAGLAS CONTRACTING uses fully tested and certificated systems.

Fabrication and installation

SOLAGLAS CONTRACTING offers a skilled and professional aluminium fabrication operation, providing nationwide coverage from ISO 9001 accredited manufacturing sites.

Mullions and transoms are square cut from sections of aluminium alloy 6063 T6 and conform to BS 1474.

The transom to mullion join can be fixed in a number of ways depending on the site conditions and constraints:

  • spigot
  • block
  • penetrating A pressure plate holds the infill in place and allows drainage and pressure equalisation using slots.

The external capping provides a neat finish and is available in a variety of profiles and sizes to suit needs. The curtain wall sections are thermally improved using an integral thermal strip, made from EPDM, which separates the internal box from the pressure plates and external cappings. All infills are dry glazed using EPDM gaskets both inside and out. Setting blocks are used between the bottom edge of the glazing unit and the frame to support and centralise the unit in the opening.

Tolerances in fabrication are in accordance with BS 4873.

Effective joint design

Careful attention to detail is the hallmark of a sound curtain walling system. Joints throughout the façade must be designed to allow for:

  • even distribution of the weight of the glass panel and wind loads upon it
  • resistance to all loads without distortion
  • retaining weather-resistant properties
  • allowance for differential thermal movement
  • preservation of environmental control properties
  • means of maintenance
  • design requirements

Framing materials


In commercial buildings aluminium is the predominant framing material because of its:

  • high strength to weight ratio
  • flexibility of design and colour options
  • high resistance to corrosion
  • good cryogenic properties

Aluminium is also eminently recyclable without losing quality. The strength of aluminium varies ending on the addition of small amounts of other metals. Profiles predominantly used in framing are extruded from aluminium alloys 6063 T6 and conform to BS 1474.

Sections used for curtain walling and window frames are formed by extrusion. Hot aluminium, between temperatures of 400-500°C, is forced through a carefully engineered die. It comes out of the extrusion process with a smooth surface protected by a natural oxide coating and is known as a ‘mill finish’. Aluminium in this state cannot be relied upon to keep its appearance in wet corrosive atmospheres. Although the structural integrity of the aluminium will not be affected, either painting using a polyester powder or anodising can protect the surface and provide a great range of colour finishes.


Fixing brackets are manufactured from rust proofed steel or aluminium as dictated by the design of the installation.

Brackets and fixings are designed by SOLAGLAS CONTRACTING specifically to suit the project’s requirements.


Curtain walling systems are not normally required to provide fire resistance unless specified. Such systems are not normally composed of materials which readily support combustion, add significantly to the fire load, and/or give off toxic fumes.

Approved Document B of the Building

Regulations relates to fire safety. External walls and roofs require adequate resistance to the spread of fire in the external envelope, and that the spread of fire from one building to another is restricted.

Key criteria when considering curtain walling:

  • Overall size and dimensions
  • Transom / mullion spans
  • Fixing points
  • Wind speed and loading
  • Glass specification
  • Guarding
  • Manifestation
  • Environmental control
  • Surface finish
  • Flashing / cill detail

For more information, contact SOLAGLAS CONTRACTING.

Windows are an effective means of introducing daylight into buildings. The incorporation of opening ventilators allows natural ventilation.

The quantity of light available in the internal environment depends, of course, on the meteorological conditions, the season and the time of day, and orientation.

These conditions will be taken into account along with any external obstructions, in order to calculate the size of windows and choose an appropriate glass type.

Glazing methods

All installations are checked and audited as part of the our Quality Management System to meet the requirements of ISO 9002.

Design criteria

Successful design solutions bring together and balance aesthetic objectives in terms of shape, colours and texture, with functional performance and quality in terms of thermal insulation, reduction in solar heat gain, light transmittance, sound reduction and degree of weather resistance.

A variety of appearances can be developed for the facade by altering the type and configuration of the windows:

Single frames anchored to the surrounding structure.

Structurally coupled mullions and transoms used to construct larger expanses of ribbon windows either vertically or horizontally.

Frames that incorporate a mixture of fixed and opening lights in a module or opening lights incorporated into a curtain wall façade.

The balance between the proportion of glass to framework and the surrounding cladding can be manipulated to create features and ensure an unobstructed view.

Window opening styles

A number of different individual window options are available to control ventilation.

Large openings permit rapid change of air, whereas smaller openings allow for a slower, more regulated and controlled exchange.

Various opening styles are available to further regulate ventilation. When selecting the window opening style it is important to consider cleaning and maintenance.

Above the second or third storey, windows can be selected that can be cleaned and reglazed from inside even though it may be externally beaded.
Top and Side Hung

Windows using butt hinges in conjunction with a hold open stay cannot be cleaned from the inside.
Bottom Hung

The Bottom Hung window is hinged in the bottom two corners and opens inwards to allow draught-free ventilation.

Projected Top Hung and Projected Side Hung

When the opening light is fully open the friction stays allow a clearance between the outer frame and the casement which facilitates the cleaning of both sides of the glass.
Top Swing Reversible

The opening vent is hinged with friction stays, which allows the bottom of the vent to open outwards. The hinges are designed to rotate the opening vent through a nominal 180° outside the opening to allow forcleaning.

The top swing gear has an automatic safety restrictor, which restricts the initial opening. The restrictor must be released to close the window or to be fully reversed for cleaning.
Tilt and Turn Window

As the name suggests, the Tilt and Turn window operates in two ways:

• in the tilt mode the opening vent is hinged in the bottom two corners only, permitting the top of the vent to

open inwards. This provides

draught-free ventilation

• in the turn mode the opening vent is hinged on the designated jamb, which allows the vent to open inwards in a side hung condition for cleaning.
Horizontal/Vertical Pivots

A horizontal pivot window refers to the placing of the pivots, opposed horizontally. Vertical pivot windows would have the pivots vertically opposed.

The friction of the hinge should be strong enough to hold the window in any open position. The pivot window provides good control of ventilation.

Some pivoted windows fully rotate to allow cleaning from the inside.
Vertical Slider

The sashes in modern vertical sliding sash windows are hung on spring loaded sash balances.


Wind loading

The appropriate frame section must be established from site conditions. Wind loading, supported pane area and height determine the selection of the mullion. The glass infill panels must be chosen so as to withstand the deflection caused by the wind. The correct choice depends on pane size, dimensions, support and wind load.

Further information on wind loading is available in the Façades section.


SOLAGLAS CONTRACTING uses fully tested and certificated systems.

Fabrication and installation

SOLAGLAS CONTRACTING offers a skilled and professional aluminium fabrication operation, providing nationwide coverage from ISO 9001 accredited manufacturing sites.

Sections of aluminium alloy 6063 T6 and conforming to BS 1474 are used for window frames. These sections are normally thermally improved using resin or polyamide insulation techniques.


Friction stays are the most extensively used type of opening mechanism on open-out windows. Concealment of friction stays within an internal rebate

eliminates obtrusive looking fittings that detract from the window’s aesthetics and their use allows for a full weather strip.

Friction stays are manufactured from type 430 Ferrectic stainless steel [BS 1449: Part 2] which is corrosion resistant in most atmospheric conditions.

The friction stay in situ gives varied degrees of openings and is available with integral restrictors if a standard degree of opening is required. Butt hinges are suitable for large opening vents.

A wide range of locking mechanisms is available:

  • locking or non-locking Cockspur handles with or without night vent facility
  • espagnollette with locking options
  • fold over openers
  • winding gear
  • spring catches.