Spray foam insulation for steel portal frame barns — bonds to purlins, cladding and liner trays
Portal frame steel buildings are the UK's most common modern agricultural structure — but without proper insulation they suffer severe thermal bridging through the steel frame itself, causing condensation at every purlin and rafter.
Steel purlins, rafters and columns conduct cold directly through the building envelope. Spray foam encapsulates the steel, breaking the thermal bridge completely.
Single-skin and thin liner trays on portal frame roofs regularly sweat — dripping water onto stored goods and livestock. Spray foam applied to the liner tray eliminates this permanently.
A well-insulated portal frame building retains heat far more effectively — reducing fuel costs for heated livestock buildings and maintaining stable temperatures in food production environments.
Spray foam is particularly well-suited to portal frame construction because it can encapsulate complex structural geometry that rigid board insulation cannot address:
For insulated panel (PIR) buildings, spray foam can be used to repair failing panel joints, seal penetrations and upgrade insulation values without full panel replacement.
| Building Use | Recommended Thickness | Target U-Value | System |
|---|---|---|---|
| Cattle housing / dairy | 50–75mm roof, 50mm walls | 0.35 W/m²K (roof) | Nexseal LE closed-cell |
| Poultry / pig units | 75–100mm roof, 50mm walls | 0.25 W/m²K (roof) | Nexseal LE closed-cell |
| Machinery stores | 50mm roof only | Condensation control | Nexseal LE closed-cell |
| Grain / produce stores | 75mm roof + walls | 0.25 W/m²K | Nexseal LE closed-cell |
| Farm offices / welfare | 100mm full envelope | 0.18 W/m²K | Nexseal LE + DC315 |
WUFI modelling available: For controlled-atmosphere grain stores, food production buildings and BREEAM projects we can provide WUFI Pro moisture modelling to confirm hygrothermal performance of the proposed build-up before installation.
Yes — this is our most common agricultural application. Spray foam is applied to the inside of the existing roof and wall cladding without any structural work, penetrations or scaffold from outside.
Yes — Nexseal LE closed-cell spray foam adheres strongly to clean galvanised steel. Surfaces must be free from oil, dust and loose scale. We prepare surfaces as required at installation.
For complex geometries with purlins, bracing and gable details, spray foam is significantly superior to board insulation — it eliminates every thermal bridge rather than leaving cold spots around each structural member.
Agricultural buildings under 30m² gross internal floor area used solely for the housing of livestock or storage of crops are exempt from Part L of the Building Regulations. We can advise on your specific situation at survey.
Yes — where existing PIR sandwich panels have failing joints, damaged sections or insufficient insulation values, spray foam can be applied to the inner face to supplement performance and seal all air leakage points.
Fixed-price quote within 48 hours. No obligation.
Talk to an expert — same day when possible.
Tell us about your building and we’ll recommend the right system — foam, waterproofing or both — surveyed, specified and quoted at no cost.
