This guide takes a closer look at shrink wrap plastic sheeting and how it compares to other methods of covering a temporary roof. We compare performance in areas such as project planning, speed of fitting, weather resistance and appearance. Read on to see if shrinkwrap is right for your next project and get some tips and tricks to help make sure your next temporary roof cover is successful.
A temporary roof is usually used to create a weather protected covering for a building project. There are a variety of sheeting options for cladding a temporary roof including tin or zinc roofing sheets, (often referred to as ‘CI sheets’), temporary roofing ‘systems’ such as Haki, Ubix etc or shrink wrap sheeting.
A controlled environment can mean different things. Sometimes it is simple as keeping a work area dry. Other times there may be more specific requirements for temperature or humidity control.
The traditional material used to cover a temporary roof scaffolding sheets of corrugated iron. Also sometimes known as tin sheets, or CI sheets, putting a ‘tin hat’ over a construction project is still used today.
After the scaffolding has been erected, sheets of corrugated iron are laid over the roof in an overlapped tile configuration and secured to the roof trusses beneath.
Used carefully, the tin sheets can be re-used on multiple jobs but they require lifting into position individually so the labour costs for fitting can be high and of course, involve scaffolders working on the roof. For an example of a temporary roof using CI sheets click here.
Keder describes a temporary roof sheeting technique that is utilised by a number of large manufacturers. With this product aluminium beams of either 1.5m or 3.0m length are fitted together up to a maximum span of 15m. Although the exact design may differ depending on the manufacturer, the aluminium beams incorporate tracks (like the track which allows a sail to be pulled up the mast on a sailing boat). Stiffening of the trusses is achieved by double and single tie bars and diagonals with snap-on ‘claws’. The bay width of this product is 2.57m. Once the beams are installed, the sheeting with sealing beads (Keder) is pulled through tracks in the beams.
For a really in depth explanation of Keder sheeting systems click here.
Keder systems is a very effective option in terms of temporary roofing. It can create a light working environment however the lack of versatility means in some cases, shrink wrap can be a better suited solution. Advantages and disadvantages of Keder are.
Although, shrink wrapping does not require the initial scaffolding design considerations of a temporary roof system such as Haki or Ubix, covering a scaffolding roof with shrink wrap sheeting will always need some planning.
Additional scaffold boards will need to be fixed securely on the roof surface to batten the shrink-wrap and a hand rail will be required around the perimeter of the roof to provide edge protection and to provide a point for anchoring safety lines for additional fall protection.
In addition there will need to be some planning to take advantage of the best weather window as fitting shrink wrap sheeting in wet and windy conditions will significantly affect the strength & performance of the product.
Finally, your team may need some kind of shrink wrapping training to achieve the results you or your client are looking for.
Corrugated tin sheet, (CI) is generally fitted to the scaffolding structure in 2m x 1m (2 m2) sections, (after overlaps have been taken into consideration) whilst shrink wrap is generally fitted as a 7m x 15 (105 m2) sections which seems to be a clear advantage for shrink wrap sheeting in terms of fitting speed.
However, fitting a shrink wrap sheet to a temporary roof scaffolding requires more than just rolling it out over the roof. The film will need to be battened down at intervals across the roof (we recommend every 2 metres), overlaps with other sections of shrink wrap will need to be sealed by heat welding and finally the entire shrink wrap cover will need to be heat shrunk ‘drum tight’ by heating the entire area of the roof sheet using a hand held propane gas hot air gun.
Rain : In terms of stopping water ingress, shrink wrap sheeting offers far fewer joints than a tin sheet roof and any joints that are present are sealed by heat welding. Fewer gaps mean much less opportunity for rain to penetrate.
Wind : When used as a sheeting for the sides of scaffolding, shrinkwrap is generally considered to be the most robust temporary sheeting product on the market. Temporary roofs can present more of a challenge. In this case, a high wind blowing over a shrink wrap roof creates a low pressure area underneath the shrink wrap which creates a considerable upward force or suction. To prevent damage we recommend the scaffolder securely clips scaffold boards to which the shrink wrap can be battened at intervals of approximately 2 metres. (These boards, which are generally installed as a run three boards wide also provide access to the shrink wrap sheeting after the sheet has been unrolled).
Installers Tip – When battening a shrink wrap sheet over a temporary roof, we install a self adhesive strip of foam between the batten and the shrink wrap. This foam acts as a gasket to prevent any water ingress through screw holes in the shrink wrap.
A shrink wrap roof will have a clean, smart and professional appearance compared with one constructed from tin sheet and the working area underneath will be considerably lighter. By continuing the shrink wrap sheeting down the sides of the scaffolding, the entire area can be encapsulated and contained as a continous sheet. One of the main advantages of using shrink wrap sheeting as a temporary roof covering is that it is easily adapted to the size and shape of the scaffolding structure, however ‘awkward’ that may be.
One aspect to consider when comparing shrink wrap sheeting versus tin sheeting for a temporary roof covering is the time taken to remove the roof cover when the project is completed. The shrink wrap film can simply be cut off in sections and bundled for collection for recycling at the site or back at your yard. This will be considerably quicker than removing tin sheets and stacking for transport back to the yard.
No product is right for every situation or application and this is certainly true for temporary roof covers.
For the largest of temporary roofs, the ‘system’ roofs offer a number of advantages and have been tried and rested on some of the most high profile construction projects in the UK.
Shrink wrap sheeting is most suited for smaller and awkward temporary roofs.