How to Choose the Right Adhesives for Single Ply Roofing

Posted on September 15, 2022 by IKO-Team

Adhered single ply roofing systems are particularly popular in the UK flat roofing market. They are chosen for a myriad of reasons such as the aesthetically pleasing roof finish, avoiding the need to predrill into a concrete roof deck or the need for several fixing and tube lengths when installing a tapered insulation scheme. They are popular for high humidity building use applications such as swimming pools and sometimes the choice may just simply be installer preference. The selection of the right adhesives for single ply roofing projects is critically important for the performance of the roofing system.

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Right adhesives for single ply roofing


There are many choices of adhesives within the flat roofing market and some applications may require multiple adhesive choices. As we mentioned the performance of the roof may be affected by the adhesive choice and correct application. The adhesive must resist wind uplift forces as well as thermal and structural movement imposed over the lifetime of the roofing system. We should therefore consider the most common adhesive types used in single ply roofing systems and their benefits.

Single part polyurethane roofing adhesives (PU)


These are generally considered high performance adhesives that can be modified to foam to different levels depending upon the application requirement. They can be applied with a brush or a roller. For faster application spray systems such as the IKOpro Sprayfast IBA can be used for insulation. An easy application can be achieved with adhesives poured directly from the can such as the IKOpro High Performance. These types of adhesives are cured by the moisture present in the atmosphere and should not be applied in temperatures below 5⁰C.  PU adhesives are particularly suitable for flat roofing as once cured they remain strong and durable in temperatures as high as 140⁰C.

Benefits of IKOpro Sprayfast IBA roofing adhesives for insulation

  • Fast installation time and rapid drying times (30-45 mins)
  • Weather resistant long lasting bonds
  • Suitable for all insulation types
  • Low-mid tooling costs with tooling maintenance required
  • Foam structured product that requires minimum foot traffic for 10-15 mins

Benefits of IKOpro High Performance roofing adhesive

  • Easy, pour from can application and fast drying times
  • Weather resistant long lasting bonds
  • Suitable for most Insulation types
  • No tooling costs
  • Extended cure times when bonding two non-porous substrates such as multi-layer foil faced insulation boards

Two part polyurethane (PU) roofing adhesives

Solvent Based Synthetic Rubber Contact Adhesives
These are single component adhesives that are applied in two coats by brush, roller or spray; one to the back of the membrane and one to the substrate. Once the adhesive is tacky on both surfaces the substrates are pressed together and pressure is applied to consolidate the two layers. The rapid curing times help create an instant bond which is ideal for vertical applications. For example, the IKOpro Fastick has a drying time of 10-15 minutes.

Two part PU is used for details and upstands but if handled with care, they can be used to bond large field areas. Issues arise if the surfaces are too wet with adhesive which can lead to solvent blisters forming between the substrate and the membrane. Conversely, if the surfaces are too dry, it becomes impossible to get the two layers to consolidate and achieve a solid bond. Contact adhesives should not be applied in temperatures below 0⁰C.

Benefits of IKOpro Fastick  (PU) roofing adhesive:

  • Rapid drying times (10-15 minutes)
  • Weather resistant long lasting bonds
  • Suitable for all insulation types
  • High initial tooling costs, but guns are robust and long lasting if maintained correctly

Waterbased Acrylic Adhesives
These single component adhesives are brush or roller applied to the substrate. They are generally not used for adhering membranes on site as they cannot get dry in low temperatures below 10⁰C. They can however be used in factory conditions easily so are a good solution to bond membrane in offsite construction production facilities.

Right adhesives for bonding insulation boards and waterproof membranes

Insulation boards are generally bonded by applying strips or beads of adhesive to the substrate using a high foaming PU adhesive, such as the IKO Spectrabond Low Foam PU. The high foaming nature of the adhesive allows for unevenness of the substrate by filling any gaps or small ridges. The bead widths can vary depending on the product being used and the substrate that the insulation is being bonded to. The bead centres also vary depending on the wind uplift forces calculated for the roof area. They will typically be 50% closer together in the corner and perimeter zones where the uplift forces are higher. Adhesive bond tests may be required when bonding to existing substrates to ensure the suitability of the product. Consumption rates of adhesive will increase on absorbent materials such as mineral wool insulation or when bonding to uneven substrates.

Membranes are generally bonded by applying a full even coat of adhesive to the substrate (and reverse of the membrane if using contact adhesive) and consolidating the 2 materials together using pressure applied by a roller or soft broom. The choice of adhesive should reflect the type of membrane and substrates it is used to bond. Spray adhesives such as the IKOpro Sprayfast FMA or PCU contact adhesives such as IKO Armourplan PVC Contact Adhesive can also be used for both membrane and insulation board bonding. The choice of adhesive should reflect the type of membrane and substrates it is used to bond, the outdoor temperatures and the whether the application is sloped. These types of adhesives are not suitable for application when temperatures are below 5⁰C.

Benefits of Spectrabond Low Foam PU adhesive for bonding insulation boards and waterproof membranes

  • Easy application with a roller or squeegee and low tooling costs
  • Fast Drying
  • Weather resistant long lasting bonds
  • Suitable onto all types of fleece backed membrane
  • Bitumen & polystyrene compatible
  • During colder temperatures product becomes harder to apply at consistent coat weight and application speeds
  • Sloped/vertical applications need additional fixing to prevent slippage during the drying period

Benefits of IKOpro Sprayfast FMA PU adhesive for bonding insulation boards and waterproof membranes

  • Rapid application rate (up to 10 meters/min) even in cold temperatures and fast drying
  • Weather resistant long lasting bonds
  • Suitable onto all types of fleece backed membrane
  • Low-Mid tooling costs with tooling maintenance required
  • Bitumen Compatible
  • Sloped/vertical applications need additional fixing to prevent slippage during the drying period

Benefits of IKO Armourplan PVC Contact Adhesive  for bonding insulation boards and waterproof membranes

  • Easy to apply with a brush or roller, low tooling costs
  • Fast drying times and instant bond
  • Weather resistant long lasting bonds
  • Suitable for non-fleece backed PVC and vertical application
  • Drying times and application rates are affected by lower temperatures
  • Not compatible with bitumen and plain faced polystyrene insulation boards and PIR boards must be taped

Whatever the adhesive type, it’s important that the surfaces to be bonded are dry and free of dust and other loose particles and contamination. The adhesive is only as effective as the material it’s bonded to. Temperature is critical when using adhesives and they all have lower working limits. Lower temperatures tend to make the products more viscous making them more difficult to apply, they will also take longer to cure. On the other hand, in warmer temperatures adhesives will dry faster giving the operative less working time. Working methods need to be adjusted to take this into account.

All IKO Polymeric adhesives have been subjected to independent wind uplift testing to establish their suitability in our roofing systems and a wind uplift calculation is undertaken for each project to ensure that an adhered solution is suitable. To discuss adhered single ply roofing systems or selection of adhesives for your projects, speak with our technical team.


IKO-Team