Spray Foam For Flat Roofs

About Spray Foam For Flat Roof’s

High quality flat roof insulation is a vital part of protecting a building from heat loss.

Spray Foam can offer a viable alternative to using pre-manufactured insulation materials in flat roofs. Whether installed above the roof deck or to the underside, spray foam provides great airtightness.


Spray Foam creates an airtight thermal seal against heat loss


Spray Foam has excellent thermal performance per inch

Fast Install

Spray Foam is a fast and effective alternative to traditional materials

Where To Use Spray Foam For Flat Roofs

Flat Roofs generally have high-resistance waterproof protection above to prevent moisture ingress into the internal features. This makes the ventilation requirements particularly important for flat roofs. Nexseal LE Closed Cell spray foam can be used on top of a flat roof to create a warm roof provided it is suitably protected by a waterproof membrane. Alternative, Sucraseal open cell spray foam can be used under the flat roof deck provided there is either a ventilated void between insulation and deck, or a robust vapour control layer on the warm side of the insulation to prevent interstitial condensation from penetrating the insulation.


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How We Help You


Get in touch today to get the ball rolling


Let us specify the requirements for your project​


We’ll provide you with a budget price range


Use one of our ThermoFoam-approved installers


Once installed, we provide a 25-Year Product Warranty


Check out our Gallery where you will find some photographs of installations we’ve completed in the past. Whilst spray foam is insulation and not decoration, our experienced installation teams will always endeavour to provide a neat and tidy finish to the insulation. Nexseal LE closed cell is easier to achieve a neater finish whereas Sucraseal Open Cell expands at a faster rate to leave an undulated finish.


Will Spray Foam Allow My Roof To Breathe?

Depending on the roof make up and any high resistance flat roof covering, Spray Foam generally complies with BS5250 ventilation strategies provided a dynamic (or static) condensation risk analysis is produced before install. In instances where an air void is required between the insulation and roof deck, we can use a laminated card slider that the foam is applied to. This creates a natural air void for ventilation compliance.

How do you insulate Posi-Joists?

The metal web running through the joist and can make it tricky to insulate with traditional materials and therefore a seamless layer can rarely be achieved. When spray foam is used for Posi-Joists, the foam is applied as a liquid and can be joined between the joist to provide a monolithic layer. This eliminates thermal bridging and provides maximum thermal values to achieve u-value targets.

How Long Does Spray Foam Last?

Pre-manufactured insulation materials can shrink, slip and degrade, especially with gravitational pull. Spray foam is entirely different because it is manufactured in-situ, therefore spray applied to the underside of the flat roof deck. The spray foam itself remains in an inert, unchangeable state once applied and it will therefore last with the life of your property.

Can I insulate a flat roof void from inside my home?

It’s common for us to help customers who had flat roof extensions added to their homes in the 1980’s and 1990’s where good insulation wasn’t really considered. In these scenarios, we can minimise disruption to your home by drilling small holes approx. 500mm apart throughout your ceiling where we inject our open cell spray foam to fully fill the empty void. This will add substantial thermal performance to help you live more comfortably.

How Long Does The Process Take?

Provided access is good and the depth/type of insulation required, around 200m2 of open cell insulation can be installed each day and 100m2 of closed cell insulation. Considering many construction projects take several days to insulate with wastage to dispose of, Spray Foam insulation can truly help to speed up your project. Less disruption, less wastage and a compliant system.

Can I Use Spray Foam Externally?

Yes, you can use our Nexseal LE Closed Cell Foam on top of the flat roof deck. The product is rigid and high resistance which makes it a perfect insulation solution for a strong and stable roof. However, Nexseal LE must be protected with a waterproof layer as with any type of external flat roof insulation.

Our Products

Check out our BBA Certified Spray Foams

Our range of open and closed cell spray foams are industry-leading, BBA-Certified, use recycled materials and contain water-based blowing agents.

Nexseal Closed Cell

This low exothermic, high-lift closed cell foam boasts a fast installation time, offers incredible thermal performance and improves the structural integrity of a building. Loved by installers for its fast rise, Nexseal is ozone-friendly and is pending BBA certification which is due in June 2022.

Sucraseal Open Cell

The leading open cell foam now available in the UK. Sucraseal combines peace of mind British Class 1 fire safety with exceptional thermal performance and is pending BBA Certification which is due in June 2022. Sucraseal is installed exclusively by ThermoFoam-approved contractors only.

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