How to Shrink Wrap your Scaffolding
Why do you want your scaffolding shrink wrapped?
Before you begin the task of shrink wrapping you need to determine what outcome you expect from it, as it will affect the manner in which your shrink wrap is installed to achieve the desired outcome. As a norm most contractors and scaffolders aim to achieve any of the following:
Sturdy temporary weather protection:
One of the biggest benefits of using shrink wrap is its ability to become drum tight through heat application, which makes it fit exactly around any scaffold structure and does not flap around in the wind. Additionally, shrink wrap is attached firmly, through welding around scaffold tubes and back on itself. It makes it extremely durable. This obviates the need for the contractor to visit the site frequently in inclement weather to check for damages, saving both time and money.
Ensure containment to protect the environment:
The use of traditional style scaffold sheeting called Monarflex, involving sheet strips around the scaffold. This invariably results in overlapping which only provides limited containment of debris and dust and is inadequate for abrasive blasting operations when the resulting dust can release toxic chemicals into the environment. When you use shrink wrap it also covers welded joints between sheets that provides total encapsulation of any structure.
When working on high profile projects including public spaces shrink wrap is a popular choice because it creates a smart professional appearance with no flaps hanging around. Of course, when you intend to use shrink wrap the layout and setup have to be meticulously planned so that the shrink wrap works perfectly and can exceed expectations.
Check for weather conditions before wrapping
After the shrink wrap is applied it is weatherproof, durable and sturdy. However, to achieve optimal results it should not be wrapped when heavy gusts of wind of more than 20 mph blow or when it is extremely wet. When installation takes place only use that many sheets that can be completed within the working day. In case of temporary roofs do not install unless the entire roof can be done during the day.
Shrink Wrap – Types of Materials & Equipment
Kinds of material to use
The best material for shrink wrap is a flame retardant (European EN13501 standard) 300-micron thick wrap that is ideal and most commonly used. It comes with a 1.8-metre roll that when opened is 7 metres in width and 15 metres in length. There are many construction sites across the UK where some temporary protection material labelled as a flame retardant to LP1207 and LP1215 standards. This is proof that the material has undergone stricter flame retardant certification.
The reason why many contractors do not opt for it because of the extra cost involved. If the insurance company asks for the use of LPS flame retardant material, you need to check first with the customer as to their exact requirements and getting the exact specification shrink wrap as stated by the insurance company. While white shrink wrap is standard, clear and other coloured sheets are also available if needed.
Type of equipment needed
The most vital piece of equipment is a hot air gun used to seal or weld joints of the shrink wrap and to make it drum tight. It is connected with a hose to a propane cylinder. While the hose could be of any length the ideal is between 8-10 metres. Opting for anything shorter means having to move the cylinder around and an extra long hose will lead to it getting entangled.
The heat gun is hand held and operated by a squeeze trigger that permits the flow of propane that mixes with air. Squeezing the trigger completely creates a spark that ignites and creates a flame. While it looks a bit intimidating using it is easy. The operator has to keep the trigger pressed at times to keep it working. The moment the trigger is released the gun will cease to operate.
Whatever your preference of heat gun it needs to be safely stored to keep it clean and prevent damage. Before using it always check the hose for wear or damage signs.
Hanging Shrink Wrap
When you hang shrink wrap it has to be hung on the inside of the scaffold even if done for a temporary installation. While there is the option to install sheeting rails particularly for scaffold shrink wrap sheets, hanging it around the handrail saves time. When using shrink wrap sheeting the maximum unsecured drop is up to 3 lifts. As an extra bit is needed for overlaps (for welding) around 7.5 metres is perfect. To make it more convenient the entire roll should be unrolled on the ground level and fold it back the same way. If you cut a 15 m roll, you will have 2 x 7m wide x 7.5m wide sheets, which are easier to manage to carry for wrapping and unfolding.
In certain situations, a smaller drop at the highest section of scaffolding is used with about two lifts. The benefit of a smaller drop makes it feasible to shrink the sheets tighter that makes it more secure from the risk of flapping and getting detached. The material is overlapped around the scaffolding by 30-40 cm, with a clip to hold it temporarily in place.
Welding & Joining
When traditional sheeting is used they are attached to scaffolds with elastic lies called bungees. These tend to fail in inclement weather conditions and cause the sheets to be blown away. With shrink wrap, there are no such issues as they war wind and waterproof and attached firmly by sealing the sheets together with heat. While the scaffold tube is encapsulated the shrink wrap does not stick to the scaffold. It is much more durable because of the welded joints. This is mainly used on horizontal scaffold tubes. If an extra drop of shrink wrap is needed below a joint is needed.
Attaching the shrink wrap to the scaffold
When we need to shrink wrap scaffolding making welded joints or seals are critical. These add to the strength of the completed shrink wrap sheeting. There are two kinds of joints to master when we need to shrink wrap a scaffold. The first is the joint to attach the shrink wrap to the scaffold. The second is used to attach shrink wrap sheets to each other.
The process of welding involves joining 2 sheets to shrink wrap through pressure and heat. For this hot air from the shrink wrapping gun is directed at the sheets between the sheets till they reach their melting point. That is when the installer presses both the shrink wrap sheets together to create a strong bond.
This joint is needed where the sheets overlap in a horizontal manner. For this generally, a double run of tubes are used that can be installed by the scaffolder or a handrail may be used for the purpose. It is installed from the scaffold top with the first sheet dropped about 6 metres (3 lifts) and welded around the lowest tube or bottom handrail. The edge of the second sheet to be installed is placed behind the lowest tube where the first is attached. The second sheet is wrapped on the highest tube or handrail and heat welded. Creating a horizontal join in this manner the sheets are attached both to each other as well as the scaffolding that creates a continuous durable bond.
These vertical joints between shrink wrap are required when the shrink wrap runs around a scaffold. While easy to do taking a little extra care can do a better job. The most common way to hang the sheet is through use of a 7-metre wide sheet around the scaffold, with a vertical join needed every 7 metres. It is straightforward with the two sheets overlapped by 30cm and heat welded.
Creating Vertical Joins
The two sheets should be hung completely vertically so that the joints are visible from outside. To get the sheet vertical take the fold lines of the shrink wrap sheet and align it with a standard or ledger. Care needs to be taken that the two sheets are welded together completely covering the overlap. The entire area of the overlap has to be heated with a consistent weld and minimum wrinkles or bubbles possible. Pat the sheets together (wearing a leather gauntlet) with adequate force applied to the heated section of the shrink wrap. However, care must be taken not to over apply force as the shrink wrap may be soft and it could tear. Also when welding shrink wrap it should be done till the edge of the sheet. Any lapse will affect the appearance and also may compromise the strength of the joint.
The hot air from the gun should be directed only on the overlap areas of the shrink wrap i.e. double thickness of shrink wrap film. If any area of single thickness is welded it could create a hole later when the wrap is made drum tight.
Tips for installation
When you try to shrink wrap in windy conditions it can get between the sheets before welding. To avoid this use a piece of shrink wrap tape between the join to keep the edge together which allows the edge to be welded. If you use high-quality shrink wrap film it need not be taped along the edge of the weld. However, if you are using regular shrink wrap you could tape the edge of the weld.
To achieve the drum-tight process heat shrink needs to be done on the scaffolding. While it is straightforward there are certain handy tips to get the best outcome. This is with using a propane gas gun although the same method could be applied with an electric shrink wrapping gun (albeit it will be slower).
Shrinking is the process of using a heating tool to blow hot air over shrink wrap film which shrinks when heated. To shrink wrap you need to hold the heating gun about 30-40 cm from the film and spread the heat over the area to be welded. There is no fixed time as it is subject to the thickness of the film and distance of the heating gun from the shrink wrap sheet. In case of windy conditions or low temperatures, it may take longer.
When you move the hot air on the film its appearance changes to smooth and glossy and it becomes flexible and soft. This indicates it has reached the right temperature to shrink wrap. At this juncture, the hot air should be moved slowly so that the entire sheet is shrunk. Care needs to be taken because if the heating gun is moved too fast it will not heat properly and cause folds or creases and not be tight. If the gun is held too long in one place the film shrinks and becomes thin. If the heat is not removed a hole is formed. While holes can be patched up with a patch or shrink wrap tape it will affect the appearance. To get the best results shrink the entire sheet of the covered scaffolding. It creates a very tight finish and spruces up the appearance. Shrinking must be done consistently by starting in one spot and shrinking the entire sheet before moving ahead.
Weather / Spot Shrinking
Do not heat shrink film in wind speeds over 20mph. This is because as it is heated and reaches its ideal shrink temperature, it becomes soft and flexible. When the heat is removed the plastic colls and shrinks firmly. When there are windy conditions instead of shrinking heavy wind blowing on a hot and soft sheet creates bubbles.
When heat shrinking use less heat in areas around a welded joint because the area of shrink wrap adjacent to a joint would have been heated when it was welded. As a result, it is easier to create a hole when heated a second time during the shrinking process. Do not shrink wrap over scaffold fittings directly.
Repairs, Doors & Handover
Once the task is completed you need to inspect it. Check if the overlaps and joints completed are heat welded tightly. Check if the sheet is thoroughly heat shrunk. This can be checked by tapping the sheet, which should sound taut and tight. There should be no wrinkles or creases.
Minor repairs of Shrink Wrap Sheeting
Even professionals make mistakes with an occasional hole appearing in the shrinking or welding process. This can be repaired using shrink wrap repair tape and also can be used on locations where the scaffold tube protrudes through the film. The norm is a patch or shrink wrap repair tape is 100 mm in width and come in a 33 m roll. Use tape with high tack adhesive which will stick even at low temperatures.
One of the main advantages of shrink wrap sheets for scaffolding is it makes it possible to make a completely sealed repair, even in large areas. When done the repair should be strong and tight like the original. A tight and moulded drum fit removes the risk of it flapping and detaching.
When repairing a large hole cut a piece of new shrink wrap film that can overlap the damaged section by 40-50 cm. Initially, use tape to keep the patch in place. Use the heat gun to weld the patch to the sheet. Ensure that the overlap between the patch and the sheet below is thoroughly welded. One way to accomplish this is to direct heat between the two pieces to be joined. After heating it to its melting point press them together with the two pieces of film and direct more warm air from over the welded area from outside. The patch should be wrinkle free and smooth without any flaps or bubbles. After the shrink wrap patch is welded the patch can be shrunk drum tight. Shrink wrap or repair tape is to be used to tape the edges of welded areas. Ensure that it is dry and clean.
Install Access Doors
Having a zipped access door is not always essential but used where scaffolding must be sheeted for full environmental containment. E.g. painting and shot blasting. While there are 2 kinds of doors the one you opt for is subject whether you need for equipment or personnel.
Hatch for personnel
It has a U shaped zipper sewn into a polythene rectangle. Typically it is 0.9m wide x 1.8m door or a smaller 0.9m wide x 1m high hatch type door.