Lifting EquipmentRoofs

Roof Glazing & Structural Glass

By February 28, 2020March 17th, 2020No Comments


At 1st Folding Sliding Doors, we provide glass options for various glass products. Please note the minimum glass standard we use is heat soaked toughened glass in all our roof glazing and structural glass. However, Detailed below is a description of what safety glass options are available and their advantages and disadvantages. When specifying such products, guidance is taken to ensure that the correct specification used for the intended use.

Toughened Glass Advantages

  • 4-5 times strong than standard glass
  • Break safe characteristics. Should the glass break, it disintegrates into small fragments known as dice
  • Resistant to breakage due to thermal stress

Toughened Glass Disadvantages

  • 4-5 times strong than standard glass
  • Break safe characteristics. Should the glass break, it disintegrates into small fragments known as dice
  • Resistant to breakage due to thermal stress

Laminated Standard Glass Advantages

  • Security. The glass has a bonded plastic interlayer which is very difficult to penetrate.
  • Break safe characteristics. Should the glass break, the broken glass stays stuck to the interlayer reducing the risk of injury and stays held in the window frame.
  • There is no risk of nickel sulphide induced breakage.

Laminated Standard Glass Disadvantages

  • Only as strong as standard non-safety glass
  • Susceptible to breakage due to thermal stress, particularly in roof glazing
  • Cracks appear due to movement in the properties structure. Breakages under these circumstances are not covered under warranty.

When quoting for roof or frameless glass, this specification is used as a standard by 1st Folding Sliding Doors.

Heat Soaked Toughened Glass Advantages

  • 4-5 times strong than standard glass
  • Break safe characteristics. Should the glass break, it disintegrates into small fragments known as dice
  • Resistant to breakage due to thermal stress
  • Massively reduced risk of nickel sulphide induced breakage

Heat Soaked Toughened Glass Disadvantages

  • If broken, the small fragments can fall if in roof glazing
  • Increased cost and lead times, however, included as standard in all our roof and glass structures.

Heat Soaked Toughened Laminated Advantages – *Recommended

  • All the advantages of toughened glass
  • All advantages from laminated glass, but won’t crack due to thermal fractures.
  • Massively reduced risk of nickel sulphide induced breakage
  • If the unit breaks for any reason other than an item impacting the unit, the glass will not break and fall into the room.

Heat Soaked Toughened Laminated Glass Disadvantages

  • The only disadvantage is the cost. You are required to pay more for this combination as it is the best combination for safety and quality

What are nickel sulphide inclusions?

Nickel sulphide inclusions are a rare but naturally occurring impurity in the manufacture of glass that can cause the toughened glass to break months or even years after manufacturing. The inclusions are so small that they are impossible to see in the glass. Over the years, glass manufacturers have implemented many raw material and process control procedures to minimise the possibility of NiS inclusions in glass. They, however, can never be eliminated.

Identifying nickel sulphide induced breakages

When toughened glass breaks, a butterfly wing formation occurs at the origin of the breakage with the fragments radiating from this point. A common misconception is to assume this butterfly wing formation is the hallmarks of a nickel sulphide induced breakage. This pattern can is seen with Impact damage and other inclusions in the glass. To confidently identify a true nickel sulphide induced breakage, the butterfly formation must is sent off for precise laboratory analysis. Even so, Nickel sulphide induced breakage is a genuine risk and causes on average one breakage in every 265m2 of toughened glass.

Heat Soaking

You can reduce the risk of a nickel sulphide inclusion breakage by putting the glass through a process named Heat Soaking. The Heat Soaking process includes thermally treating of the glass after the toughening process, in large heat soaking ovens. The glass is heated to high temperatures to force panes with Nickel Sulphide impurities to break. The resulting glass that survives the testing, therefore, has a lower chance of containing a Nickel Sulphide Inclusion, reducing the risk of broken panes to the end-user.

You should note that the Heat Soaking process does increase the cost of the glass. However, it reduces the risk of a Nickel Sulphide Implosion down to 1 in every 26,500m2 of heat soaked toughened glass. This specification is included in all our roof glass quotes at no additional cost by us.

Any toughened glass used on a project can be specified as Heat Soaked by the architect if you are worried about Nickel Sulphide Inclusion.

So heat soaking toughened glass massively reduces the risk of nickel sulphide induced breakage, but doesn’t entirely eradicate the risk nor does it stop toughened glass breaking due to other types of inclusions or impact damage. 1st Folding Sliding Doors heat soak all toughened glass that goes into our rooflights as a duty of care to all our customers. Not all companies can say they offer this new process as standard. However, if there is a concern by the low-risk heat soaked toughened glass falling from a rooflight should it break, potentially causing expensive damaged furniture or causing injury you might want to consider a laminated heat soaked toughened glass. Laminated heat soaked toughened glass is our best performing glass makeup as it takes all the benefits of heat soaked toughened glass, but because it is laminated with a plastic interlayer in the improbable event of the glass breaking the bond to the interlayer holds the glass in place stopping it from falling. Laminated heat soaked toughened glass does come at a cost, but it truly is the safest glass available on the market, giving you peace of mind should the unthinkable happen. However, there is an extra cost for this detailed in your quotation.

*Here at 1st Folding Sliding Doors, all of our overhead glass units come with heat soaked toughened, however, to achieve as much peace of mind as possible, we do recommend heat soaked toughened laminated for all overhead glass. For more information and costings contact our office and quote your sizes on; 0209 997 2448. Please note if the glass breaks nickel sulphide inclusion this is covered by your household insurance and not through our warranty. It is imperative to let your insurance company know that you have an overhead glass in place so that they can give you the right insurance policy. You should, before any works starting in your home inform the insurance company of your intentions, ensuring you are best covered.

Contact Us

1st Folding Sliding Doors Ltd
Unit 26/3 Silicon Business Centre
26 Wadsworth Road
Perivale, Greenford
Middlesex UB6 7JZ

Call: 020 8997 2448
Email us


Our West London Showroom is open Monday - Friday from 07.30 to 18.00 and Saturday's from 07.30 to 12.30. For visits outside of these times, please call for an appointment. For directions, please call or email.

Surbiton showroom is open from 09:00 to 5:00 on Saturday for pre booked appointments .

For all other times please call 0208 997 2448 to book.