How Is Polythene Sheet Used In Construction?

Updated July 2024 to include new information.

Construction is just one of the many industries that use polythene – but nevertheless, it has become one of the most vital materials used by tradespeople, site managers and at all stages of the construction logistic process. Polythene sheet is used in construction as both a permanent building material, and as a temporary protective barrier. It’s also used as packaging and as pallet covers for building materials in storage, on site and in transit.

Here’s the how (and the why) behind the use of polythene sheeting in building projects around the world.

The uses of polythene sheet in construction

Polythene might not seem the most obvious choice as a construction material, but the things that make it so good at packaging – like its resistance to moisture, insulating properties, flexibility and light weight – also make it useful in other applications.

Vapour barriers

Polythene’s moisture proof properties make it the preferred material for vapour barriers – but it’s also highly cost-effective, light and workable. The versatility of polythene sheeting means it can be applied to complex projects with more than one use in mind, from damp-proofing to concrete curing, and everything else in between.

But in high humidity areas or parts of buildings susceptible to humidity (like bathrooms), microperforated polythene film can be specified to allow the interior vapour to be drawn out.

Polythene vapour barriers are widely used in construction due to their effectiveness, affordability and ease of installation. It’s used all over a building – in walls, roofs, even loft spaces – making it a versatile solution for moisture control in different parts of a building.

Learn more about polythene vapour barriers

Protect concrete during curing

When concrete is poured for slabs or for structurally important elements, it needs to be covered until it cures. The most obvious reason to cover concrete while it sets is to protect it from getting debris stuck in it – but coverings actually serve a deeper purpose.

Temperature and moisture have a profound effect on concrete as it cures. If it cures too quickly, it can crack. That’s not only unsightly, it can be structurally dangerous.

Polythene is moisture-proof and an excellent insulator. By covering concrete with it, the water content can react with the binding agents fully before it dries off. This allows for a slower, more controlled cure with lowered risk of cracking.

The colour of the polythene is also important. Light colours reflect sunlight, and darker ones absorb it. That’s why, in hot and arid conditions, heavy duty white coloured polythene sheeting is used. In low temperatures, black coloured polythene sheet is used to absorb more heat. 

But care has to be taken when covering concrete with coloured polythene, because it can transfer colour to the concrete. Clear polythene sheeting can be used as an underlayer, and in temperate conditions, can be used by itself.

For an in-depth look at using polythene to cure concrete, read this post next:

Polythene For Concrete – How To Choose The Right Sheeting

Damp-proof membranes

Under-slab damp-proofing protects a structure from moisture coming up through the concrete. It’s extremely important, protecting against mould and damage to the building.

A heavy duty, single wound polythene sheet (of around 250 microns or thicker) offers excellent moisture protection and coverage. This makes it particularly useful as a liner and damp-proofing membrane.

High quality polythene sheeting made from virgin material is used for permanent installations like this, because the mechanical properties of polythene can be altered by the recycling process. Special polythene additives can also be used to enhance the natural water resistance of polythene, helping it hold up against prolonged contact with soil, water and concrete. We’ll touch on chemical resistance shortly, with a link to one of our resources on the chemical and physical properties of polythene.

Recycled material can be used in less critical applications – like temporary coverings and protective uses.

A temporary weatherproofing material and dust cover

Polythene sheeting can be used as a dust cover, to protect floors while painting, or to protect large, immovable pieces of furniture while works are carried out. But it can also be used to seal buildings temporarily, as they are built.

While doors, windows, skylights or roofing elements are awaiting full installation, polythene sheeting can be used to create a temporary seal from light winds and rain. This is especially useful if delays occur on site and works have to be paused while parts and materials come in.

What type of polythene sheet is used in construction?

Construction projects will typically use heavy duty or super heavy duty polythene (500 to 1200 gauge) for all installed sheeting – such as in damp-proof membranes and vapour barriers – depending on use. For temporary uses, like concrete curing and sealing off areas while a building is being worked on, lighter duties may be more appropriate.

Our handy heavy duty polythene thickness chart is here, to give you an idea of what thickness to expect:

Virgin material is also preferred for its purity, predictability and performance – especially for permanently installed polythene. Coloured polythene can be used for anything that’ll be visible from the exterior, and black polythene is often used for anything that’s moisture barrier related; it’s easier to see light passing through perforations against a black sheet than a clear or white one!

Polythene additives for construction projects

Polythene intended for installation in construction projects needs to have some additives applied – with the most crucial being flame retardants. This is because polythene is essentially the solid form of ethylene, a flammable gas. 

When exposed to heat or flame, the carbon-hydrogen bonds in polythene molecules break, releasing energy and producing complex, volatile and toxic compounds. Molten polythene can cause severe burns if it comes into contact with skin. Without flame retardant additives, polythene could contribute to worse fires in buildings, so flame retardant additives are essential in polythene for construction.

Ultraviolet light is one of the few things that attack polythene, and even if damp-proof membranes and vapour barriers may not be constantly exposed to direct sunlight, there may be times when they are, at least partially. It’s best practice to ensure all polythene sheeting for construction is designed with longevity and safety in mind, and ultraviolet inhibitor additives can help maintain integrity of polythene sheeting kept on site pre-installation, and for its usable life thereafter.

How chemical resistant is polythene sheeting?

Polythene is largely inert, reacting very rarely with other materials – but there are chemicals that can affect it. For a full rundown of the chemicals known to attack polythene, read Properties Of Polythene, which covers the fundamental operating limits of polythene and its chemical resistance.

Polythene sheet for materials packaging, transport and logistics

Due to the size and quantities of building materials required for a project, finding effective packaging solutions can be difficult – but large sections of polythene sheeting can be used to create effective coverings for construction materials at all stages of their lifecycle.

During construction, materials often need to be stored on site, where they’ll be exposed to the elements. To keep them safe from rain and dirt, polythene sheet makes an excellent covering – adding a UVI polythene additive helps to keep light-sensitive products safe when stored in direct sunlight, too.

Polythene sheet can also be used to securely transport goods on pallets, while offering the same protection against moisture, dirt and sunlight from the warehouse to the construction site.

Polythene sheet – the material with a million uses

Talk to our friendly polythene experts at NPF Packaging – and start your order for a custom blended polythene sheet. We’ll deliver your polythene sheet in any colour, and with specialist additives that meet your exact needs. Get a quote now, or call us on 01773 820415.