What Are The Disadvantages of Shrink Wrap Scaffold Sheeting?

What are common challenges associated with scaffold shrink wrap?

Why is it that when you ask most suppliers what are some disadvantages with their product or service, they seem to put on rose tinted safety glasses – Disadvantages? Our product? Never! 

Lets be honest, no product can be the perfect ‘fit’ for every situation or every customer, and this is certainly true for scaffold shrink wrap sheeting. This article explores the most common problems we experience with scaffold shrink wrap and includes some suggestions of how you can fix (or even better avoid) the problems we have found over the years. Hopefully, after reading the article you should be able to judge what are the situations when you should / shouldn’t use shrink wrap sheeting for the temporary weather protection or environmental containment of construction projects.

Not planning in advance how best to set up the scaffold structure for shrink wrap sheeting.

With traditional style scaffold sheeting products, which are generally installed on a ‘lift by lift’ basis around the scaffolding, protruding transoms, ledgers and standards do not cause much of an issue for the installation of sheeting, because the scaffold tubes stick through the sheeting at the point the strips of scaffold sheeting overlap. For shrink wrap sheeting, which is normally supplied as a 7 metre wide sheet, having to cut around protruding tubes, whilst not impossible, can affect both the appearance and performance of the finished job.

What is the impact of this problem?

Appearance

It is still a surprise to me how many scaffolders and contractors appreciate shrink wrap sheeting for it’s smart and professional appearance alone. Because of the heat welded joints and ‘drum tight’ finish, a shrink wrapped scaffolding can look very neat and different to traditional style scaffold sheeting which can start to sag and look untidy after a week or two. However, protruding scaffold tubes make it very difficult to make the scaffolding sheeting look it’s best. Although the sheeting can be cut around protruding tubes, sheeting will need to be welded back together and if the smartest possible scaffold sheeting is your goal, then you want to minimise the amount of welds and joints between sheets.

Performance

Where appearance is not so important as performance, protruding tubes cause a problem for scaffold shrinkwrap sheeting on other ways. For projects where the shrink wrap sheeting is creating some kind of environmental containment then the protrusion of tubes makes that very difficult to achieve. The installer will need to go back and use the shrink wrap repair tape to seal around the point where each scaffold tube passes through the sheeting. Whilst this solution might work in the short term, over the weeks these taped seals may start to become less effective.

Although shrink wrap sheeting will generally mould very tightly around the scaffolding structure, if there are very sharp tube fittings and scaffold tube end then over time, these can be a problem by wearing through the sheeting and creating holes. It is unlikely to affect the integrity of the entire sheet but it doesn’t look good and will obviously let water in and dust out.

There needs to be some kind of support for the sheeting! You might be surprised at the number of times we have turned up to a job to be asked to install some sheeting where there is no scaffolding structure to support and attach the sheeting to. Although shrink wrap is available in much larger widths than normal traditional style scaffold sheet it still needs a support structure underneath / behind it, at least 2 metre centres.

You need to think about how the shrink wrap installers are going to access the sheeting. It is not enough to consider that the installers need to be able to reach every part of the sheet during the installation process, either to create welds or heat shrink drum tight. This is particularly important consideration for the shrink wrap encapsulation of temporary roofs – if safe access cannot be created either to the underside or top of the shrink wrapped roof then it may be best to consider an alternative solution such as the excellent ‘system’ roofing systems provided by Haki and others.

Another ‘problem’ is that shrink wrap sheeting is not designed to detach from the scaffolding in high winds. You should also pay attention to how the scaffold structure will contain any wind loadings that will result from the installation of the shrink wrap sheeting. Whilst this is true for all types of scaffold cladding it is particularly important for shrink wrap sheeting because it is a high performance product which is designed not to detach from the scaffolding.

How to prevent problems connected with the scaffolding structure;

The simple answer is to plan the set up of the scaffold structure in advance.

Key points to remember are;

• Keep the scaffold structure flush
• Ensure the scaffold is fully boarded to create safe access to all parts of the scaffold structure that require sheeting
• For a really great looking job, install a ‘sheeting rail’, mounted on a single, around the scaffolding lift by lift, this will hold the sheeting off scaffold fittings and prevent any sharp bolts sticking through the sheeting.
• If you are using the sheeting to create a temporary roof or even just a small canopy style roof over the top lift, a tube mounted on the edge of the roof keeps the shrink wrap away from the ends of tubes and helps to prevents snags during installation.

You can read a detailed guide to setting up scaffold structure for shrink wrap sheeting here.

Not using trained operatives to install scaffold shrink wrap sheeting

Whilst traditional style scaffold sheeting products can be installed by most scaffolders without a problem, scaffold shrink wrapping, despite not being ‘rocket science’ is a specialised trade which requires some training and experience to be carried out safely to a high standard.

For example, shrink wrap sheeting requires the use of a shrink wrapping hot air tool, which is used to create welded / sealed joints between sheets of scaffold wrap and of course, to heat shrink the cladding and achieve that signature ‘drum tight’ / wrinkle free appearance which is unique to shrink wrap cladding. The shrink wrapping hot air tool or ‘gun’ is a powerful tool, which uses propane gas and so an understanding of it’s safe operation is essential.

What is the impact of this problem?

There are a number of problems connected with inexperienced operatives installing shrink wrap sheeting

One of the key skills to master when shrink wrapping is how to create a welded joint between two pieces of shrink wrap. Using the hand held shrink wrapping heat gun, the trick is to direct the hot air between the two pieces of shrink wrap film that you wish to join until they reach their melt point. The heat is removed and the two pieces of film are pressed together using a gloved hand so that they stick. Inexperienced users will tend to use insufficient heat so that the shrink wrap is not joined properly. Alternatively, an untrained installer may use too much heat and burn holes in the shrink wrap sheet.

Either way, if sheets of scaffold wrap are not joined properly the weld will be weak and may leak or not provide proper containment of dust and debris.

Another key skill involved in the encapsulation and containment of construction projects using shrink wrap is to shrink the film ‘drum tight’. Once again, the problem centres on operatives not using enough heat (wrinkles and creases remain in the sheeting and it is not drum tight) or too much heat (holes appear in the shrink wrap sheeting which need patching with more shrink wrap or shrink wrapping tape).

What is the impact of this problem?

Hopefully, the only impact of not using a trained & experienced installation team is that the sheeting looks a bit ‘rough around the edges’ but still achieves it’s purpose. However, poor quality welds and poor quality shrinking may lead to the scaffold sheeting detaching during windy conditions.

How to minimise the effect of this problem?

The best way to avoid this problem is to plan ahead and do your homework. If you are looking for a fully installed shrink wrap service, you might want to check out this article; ‘Which scaffold wrap installer is best for my project?’ which explores some of the criteria for choosing an installer and looks at the main companies in the UK providing a shrink wrap contractor service.

Alternatively if you are looking to buy the materials and equipment and carry out the work you might want further information on the skills involved you might want to read another article; ‘How do I shrink wrap a scaffolding?’

Alternatively, if you are looking to install the scaffold shrink wrap yourself to using your own teams you might want to check out this article; ‘What scaffold shrink wrap materials & equipment do I need?’

Although these articles explore shrink wrap training in more detail, in terms of minimising the effect of the problem I would advise finding a company who can provide you with training and then provide you with a trainer or experienced operatives to accompany your team on their first job.

Trying to install scaffold shrink wrap in wet and windy weather conditions

Aside from the problem of trying to handle any kind of sheeting materials in wet and windy conditions, there are a couple of aspects of scaffold shrink wrap that make getting the right weather conditions particularly important.

The main problem with attempting to shrink wrap a scaffolding structure in windy conditions is that shrink wrap scaffold cladding needs to be, well, shrunk ‘drum tight’. After all, the way shrink wrap sheeting becomes tightly moulded to and around the scaffolding is where much of the unique appearance and performance of shrink wrap sheeting comes from.

What is the impact of this problem?

To heat shrink the scaffold cladding, first the shrink wrap sheeting must be attached to the scaffolding by wrapping around tubes and heat welding the plastic back on to itself. At this point, the shrink wrap sheeting resembles traditional style scaffold sheeting, i.e. it may be reasonably tight but there will inevitably have wrinkles and creases and will certainly not be as ‘tight as a drum’. To get the shrink wrap sheeting ‘drum tight’, the operator uses the propane gas hot air gun to blow hot air over the surface of the sheet. If you were watching this process you would see the appearance of the shrink wrap change and become quite ‘glossy’. It is also quite soft and flexible and then as it cools, it shrinks and hardens. The problem with shrink wrapping a scaffold in windy conditions is that during the heat shrink process, if the wind can blow on to the shrink wrap as it is in the ‘hot and flexible’ stage, before it has had a chance to cool and harden. When this happens, instead of shrinking tight, the shrink wrap expands into a bubble. The only way to fix this is to heat weld a patch of shrink wrap over this area and try shrinking again but the appearance will not be as good.

Secondly, unlike traditional style scaffold sheeting where sections of scaffold sheet are simply overlapped and bungeed to the scaffolding, (leaving gaps between the sheets for water to enter or dust to escape), two sheets of shrink wrap are joined by overlapping them by about 30cm and then heat welding the two sheets of scaffold wrap together to make a completely sealed joint. (You can see a video of this process by clicking here). Once this join has been made, it should be as strong as the original sheeting and it should be impossible to pull the welded shrink wrap joint apart. However, when shrink wrapping in very wet conditions, if rainwater gets between the overlapped area before the weld has been made, then it can be more difficult to get a strong and robust joint. It should be noted, that this applies to very wet conditions, and is more of a problem where shrink wrap sheeting is being used as a covering for a temporary roof scaffolding.

How to minimise the effects of this problem

One aspect of the weather is that sometimes it is better to delay starting a job until the weather is right, particularly with roofs. I know this can be a difficult decision to make, particularly if a client is applying pressure on you to complete the work as soon as possible, however, pressing on regardless can often cause more problems in the long run. For example, installing a section of shrink wrap sheeting at then end of a working day when it is too windy to shrink it tight and more windy conditions are expected overnight, may just lead to the section flapping and becoming damaged beyond repair overnight, so that it has to be replaced. In this scenario it would be worth waiting until the sheeting could be hung and heat shrunk drum tight.

Using a good quality shrink wrap sheeting (one that has been designed to shrink powerfully in all directions) can reduce the problem of windy conditions, and using a shrink wrap sheeting that welds powerfully can also help, but ultimately this is something you should always bear in mind and if your project has only one ‘window of opportunity’ to apply the cladding sheeting, then shrink wrap may not be the best choice.

Poor quality shrink wrap sheeting

If you would like to explore the importance of scaffold shrink wrap quality to your jobs then we have written a much more detailed article here; ‘Understanding Shrink Wrap Quality’

What is poor quality sheeting? In terms of scaffold shrink wrap poor quality generally manifests itself in two ways.

1. Very difficult to weld / welds start to come apart after a period of time
2. Shrinkage is weak or not consistent (i.e. sheeting shrinks lots in one direction but not much in the other direction) which makes it difficult to get a ‘drum tight’ wrinkle free appearance.
3. The mechanical strength of the scaffold sheeting is low. We explore this in more detail in this article – ‘Will Scaffold Shrink Wrap Fail in Strong Winds?’ What this means is that wind loadings cause the shrink wrap to stretch beyond the point of no return.

What is the impact of this problem?

However, bottom line is that poor quality shrink wrap sheeting affects jobs in a very similar way to poor quality installation

• Sheeting may detach from the scaffolding
• Joins  / welds between sheets may open up
• Sheeting may look tired, with many wrinkles and creases.

How to minimise the effect of this problem

Once again, the main thing is to do your homework. Although it is rather tedious and time consuming, ask your suppliers for the specification and data sheet for the shrink wrap sheeting and compare it between suppliers. Although the can be rather overwhelming, the main issues to focus on are shrink ratio (which will give you an indication of how tight the sheeting is likely to be after shrinking) and yield strength (which will tell you how much wind the sheeting is likely to take before it becomes loose and saggy).

Thank you for getting this far! Because scaffold shrink wrapping is such a specialised trade it can be difficult to find straightforward advice that is not just sales ‘blurb’.