Building type
Barns, grain stores, livestock and machinery sheds, with metal or fibre-cement roofs. On a cold morning the sheet drips onto whatever the building holds; whenever the building is heated, the heat leaves through the same sheet. What forms, what it costs, and how the work is done around a farm that does not stop.
01What is happening
A livestock shed is one of the wettest buildings there is: animals breathe out water all night, bedding and feed hold it, and the air under the roof carries it. A grain store or machinery shed is drier but still lightly warmed by what it holds. On a cold, still morning the sheet is the coldest surface in the building, below the dew point of that air, and the water comes out of the air onto the sheet and drips.
It is not a roof defect. Repairing or replacing the sheet will not stop it; a new sheet is just as cold.
It is not solved by ventilation alone. Ventilation moves the moist air; it does not warm the sheet the air meets. Livestock buildings still need their ventilation, and the layer does not change that.
It is not always condensation. Water at a lap, a fixing or a rooflight during rain is ingress, and that is repaired first, by someone else.
02Recent projects
Installation footage and photographs from HOLVEM's own farm projects: an arched steel building sprayed to the roof and walls, a Nissen hut, a silo, and a corrugated farm roof sprayed from beneath. Every item is a project record; press play to watch a clip.
Written records, with their figures and the basis each one rests on, live on the project pages.Project records
03What is applied
The existing sheet stays as the weather line, metal or fibre-cement. The layer is applied from inside in passes, follows the corrugations, closes the side laps and encapsulates the fixings and purlin flanges. The purlin continues through the layer and remains a thermal bridge; the calculation accounts for it rather than ignoring it.
Schematic / not to scaleKeyed 1 to 5 below
The weather line, and it stays. We do not replace it and we do not make it watertight. A fibre-cement or asbestos-cement sheet is not walked on, cut or removed.
Loose material, dust and contamination removed. Adhesion is decided here, not later.
Follows the profile and closes the side lap. λ 0.027 W/mK is the NexSeal LE product figure, not a HOLVEM performance figure.
Encapsulated by the application, and still a thermal bridge.
B-s2,d0 belongs to the coated NexSeal LE and DC315 system, as tested. Where the coating is not applied, that classification does not carry.
A metal roof: the build-up in sequenceA fibre-cement or asbestos-cement roof: encapsulation
04Enverge NexSeal LE
Enverge NexSeal LE is a two component closed cell polyurethane, spray applied directly onto the prepared substrate. As it cures, it expands and sets into one rigid, continuous layer, bonding into corrugations, laps, fixings and awkward junctions without being cut, jointed or mechanically fixed. On a farm roof that is the corrugation, the hook bolt and the lap at every sheet.
That matters because most insulation problems start at the gaps.
Board systems can leave voids at ribs, laps and junctions, and every gap is a potential cold bridge where warm internal air meets a cold surface and condensation forms, hidden behind the insulation. NexSeal LE is applied as one continuous bonded layer, so there is nowhere for that to start: a sealed, stable building envelope that controls condensation, reduces heat loss and protects the structure underneath.
HOLVEM also installs open-cell foam. It is a different product with its own data sheet, specified for different objectives; it is not what goes onto a cold roof underside or a concrete soffit. Open-cell system data · Closed-cell system data
05Working around a live farm
The roof is never opened, so there is no weather window and nothing above the sheet changes. What has to be planned is what is beneath it: which part of the building is released to us, what moves or is sheeted, and when the farm can spare it. Step through how a job runs; the section drawing follows each step.
Schematic / not to scaleThe drawing follows the step selected above
The roof stays weathertight throughout. The sheet above is never opened.
Containment beneath the spray zone. The layer goes on inside a sheeted area; nothing beneath it is sprayed by accident.
Livestock are not in the bay being sprayed. Where and for how long they move is agreed at the walk-round.
Feed, grain and machinery under the work are moved or sheeted. A store is easiest between harvests; a livestock building is easiest when it is turned out.
Ventilation openings and rooflights are left working. The layer stops at a closed edge short of each one unless you ask for them sealed.
Each step is agreed before the next begins. Where the building cannot spare a bay on the day, the work stops and comes back; it is not sprayed anyway.