21 Jul Joining Shrink Wrap? Stop Taping Welds!
How Are You Joining Shrink Wrap?
One advantage of using a shrink-to-fit scaffolding sheet compared with ‘traditional style’ scaffold sheeting is that no elasticated bungee ties are required; sheets of shrink wrap are secured to the scaffolding structure by wrapping around a scaffold tube and heat welding the overlap back on to itself. (Watch a video of this process here).
In addition, overlaps between sheets of shrink film are heat welded together which creates a ‘continuously bonded skin’ around a scaffolding structure. Sealed joints between sheets makes scaffold shrink wrapping useful for projects that require a high level of environmental containment.
Because of the importance of joints when encapsulating a scaffolding with shrink wrap sheeting, I am often askedby scaffolders and shrink wrap installers about whether they should use shrink wrap repair tape, often called ‘patch tape’ to tape along every edge of the shrink wrap sheeting where it has been joined (heat welded) to another sheet. The simple answer is, no! If you are taping along the edge of the sheet then you are probably wasting both time and money.
To show how using patch tape can really make a difference to your costs of encapsulating scaffolding consider the following example;
A scaffolding project that is 12 metres high by 50 metres long would typically be shrink wrapped using two ‘drops’ of shrink wrap sheeting, (6m drop plus 6m drop), with an additional vertical join at least every every 15 metres. Shrink wrap repair tape / patch tape is normally supplied on a 100mm wide roll with a roll length of 33 metres, (although patch tape roll lengths of up to 55 metres are sometimes available.)
To tape every horizontal and vertical weld would require at least 250 metres of patch tape which even on this small area is equivalent to nearly 8 rolls of patch tape or a cost of around £80.00, (and this doesn’t include the cost of labour needed to tape all those welds either!)
Why do some shrink wrap installers tape shrink wrap joints?
Poor quality shrink wrapping sheeting
Low quality shrink wrap sheeting can have a major affect on the strength of heat welded joints. Typically, when first welded the shrink wrap can look as though it has been joined properly. However, after some time, the welded joint begins to separate and is easily peeled apart by hand. By taping the weld, the installer hopes to slow or stop the weld peeling part.
My advice is to choose a supplier who can consistently supply a scaffold shrink wrap that when welded / joined – remains bonded with a joint strength greater than the original material. If the shrink wrap remain welded then it will require no additional reinforcement using adhesive tape.
In my experience the price of genuine scaffold shrink wrap film is not much more than some of the cheap imitations, and when you factor in that you will not require to buy as much patch tape, using a high quality scaffold wrap might actually work out as costing less than the low quality ‘packaging’ grade shrink wraps.
Lack of scaffold wrap training
No matter what shrink film you use, it is important to understand how to use the hot air gun properly to create a robust weld. Welding involves heating two pieces of shrink wrap film close to their melt point using a hand held shrink wrapping gun. When this point is reached, normally noticeable by a smooth and glossy appearance, (and possible slight colour change), to the shrink wrap material, the operator presses the two pieces of shrink wrap film together and after a few seconds, the shrink wrap cools and is bonded.
A welded joint between two pieces of shrink wrap film should be smooth, with as few wrinkles or air bubbles as possible. However, if the operative does not use sufficient heat or heats the plastic for too short a period, the melt point will not be reached and a proper bond will not be achieved. Trying to weld / join scaffold sheeting that is very wet or dirty may also create a join that is on insufficient strength.
If you feel you need some scaffold shrink wrapping training, ask your supplier for help or guidance. They may even be able to send out an experienced scaffold wrap installer to get you on track!
Temporary Roofs – The Exception!
There is one important exception to the ‘no taping’ rule and that is where shrink wrap sheeting is being used as a temporary roof covering.
The technique recommended by our own installation team is to start the roll of tape at one end of the weld. As the heat gun is used to weld the sheets together, the tape is unwound, bit by bit, in one continuous strip along the edge of the welded joint. The advantage of taping the weld as you go is that when the shrink wrap plastic is still warm, the tape will stick to and mould to the shrink wrap sheeting. This is particularly important wen the shrink wrapping on low temperatures.
Taping along every join between sheets of scaffold shrink wrap used to be essential for every project. As the quality of shrink wrap materials have improved, this is no longer necessary. You should only need to tape welds if you are using poor quality material or your welding skills need a little improvement.
You will still need shrink wrap tape to make small repairs to the sheeting or to seal around locations where a scaffold tube is sticking through the sheet but you could be wasting money by taping along every horizontal and vertical join.
Thanks for reading! As always, if you liked this article, please share. If you need any help or advice with any aspect of using shrink wrap sheeting for temporary weather protection or environmental containment get in touch with myself and my team; firstname.lastname@example.org or +44 (0)1477 532222.