Glass specification mistakes that cause delays on site

Accurate glass specification is essential for avoiding delays on-site. Explore 6 common mistakes that often cause downtime.



If you specify glass for building projects, you don't need us to tell you how critical it can be for success or failure.

Often, however, the emphasis is placed on the finished result of the project and the need to avoid costly redesigns, repairs and replacements down the line.

But glass specifications are critical for the success of the construction process, too. Mistakes in the specification process can cause delays that are bad for all parties involved, both in terms of reputation and expense.

So, what are the glass specification mistakes that cause the most fuss and bother on the construction site? Let's look at six of the most common – and how to avoid them.

Six common glass specification mistakes

1. Inaccurate dimensions

This is one of the most common glass-specification errors. It covers two kinds of inaccuracies:

1. The inaccuracy of the overall dimensions
2. Failing to account for fabrication tolerances
   
   

Tolerances are a fine art and require careful thought. When specifying glass, always talk to the glass processor about your tolerance requirements.

Whether the glass arrives inaccurately sized or with the wrong tolerance levels, the result is the same: the glass won't fit.

On-site workarounds like grinding or nipping the edges to squeeze the panels in only compromise the safety and sealing properties of the glass.

That's why it's so important to check, double-check and triple-check dimensions and tolerance requirements before ordering your materials.

2. Thermal safety specification mistakes

Thermal stress occurs when ambient temperatures or shadows cause significant differences in temperature between the middle of the pane and its cooler edges. This, in turn, causes the glass to expand unevenly, in some cases leading to spontaneous thermal cracking.

This is only a problem if you fail to conduct a thermal safety analysis before specifying your high-performance solar-control glass.

When specifying materials, it's easy to overlook certain things. In this case, however, it can lead to spontaneous breakage down the line, shattering your reputation as well as the glass you installed.



3. Sealant and spacer bar errors

Insulated glass units (IGUs) use sealants and spacer bars. If you use generic, incompatible or just incorrect sealants and spacer bars, you could create problems for building users in the future.

There are two reasons for this, both caused by damage to the primary seal:

1. This damage can lead to moisture ingress and condensation.
2. The aesthetic appeal of the IGU can be compromised.
   
   

For both reasons, it's important you take care when specifying sealants and spacer bars for your IGUs.

4. Differences in elevation

Atmospheric pressure is an important consideration in architectural design. In the case of glass, neglecting it can lead to glass distortion or seal failure.

This is for one simple reason. There are sometimes differences in atmospheric pressure between the elevation of the manufacturing plant and the installation site.

If these differences are too significant, the glass can be bowed inward or outward with what's known as "edge spacer deflection".

In practice, this means you need to ensure the glass units you specify are sealed correctly. And not just for any old situation, but for the specific elevation of the place where they're being installed.

Skip this step and you could be looking at unsightly glass distortion or an IGU seal failure. Neither is good for building users, stakeholders or your firm's reputation.

5. Compliance and testing errors

Industry regulations for thermal efficiency, safety and other criteria have never been more important, and oversights have never been more harshly penalised.

This means one thing: when specifying glass, you must submit orders that contain concrete efficiency data or other conformity criteria.

This will often include:

• U-values: how much heat should transfer through the glass
• SGHCs: solar heat gain coefficients that measure the same for solar radiation
  
  

The consequences for half-baked compliance can be severe. The installation could be rejected or shut down if it gets underway. And if the project is finished without proper compliance, it could be demolished and you could receive a fine.

Compliance is a daunting topic and one subject to change. This is one key reason why you should always work with a glass processor that's not shy to mention its compliance credentials. You'll need them on side to ensure the materials you specify are the right ones for the job – and exactly the right ones at that.

6. Setting block errors

Setting blocks are essential for supporting the weight of the glass, keeping the glass centred and enabling water to drain away.

A common specification mistake, however, is to install setting blocks that are too soft or too hard. Both have negative consequences for the glass.

It's not just softness that matters, however. It's also incorrect placement. This leads to the metal touching the glass, which dramatically heightens the risk of structural failure under wind loading or building movement.

How can a glass processor help you avoid specification mistakes?

Most of the preparatory work for glass specification is likely to be done in-house.

Nevertheless, the glass processor you order from can help you to avoid costly specification mistakes that would otherwise cause delays on site.

This isn't to say that a processor will share responsibility with you. However, an experienced and accredited processor will have the technical know-how to reduce the chances of sizing errors, optical distortion, thermal inefficiency and so on.

So, when looking for a glass processor, check for accreditations. These seals of approval let you know your materials will be prepared with maximum accuracy.

Are you looking for high-quality glass for construction? At ToughGlaze, we cut, process and ship all our glass products from one state-of-the-art UK facility. Get in touch with our experts today to discuss your needs and request a quick quote.