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A Nissen hut on a UK farm at first light: the semicircular corrugated steel arch, a brick end wall with a door, frost on the grass and a pale sky.

Building type

Nissen huts: a curved corrugated roof that nothing else will line.

The Nissen hut is one continuous arch of corrugated steel. Board cannot follow it, quilt sags off it, and a framed lining eats the headroom. A sprayed closed-cell layer bonds to every corrugation of the curve, stops the drips, holds the heat and takes 25 to 75 mm from the arch, not a framework.

  • Semicircular corrugated steel arch
  • Sprayed to the inside of the curve, no framework
  • From £16/m² + VAT at 25 mm

Same-day estimator

About a minute · no obligation

Step 1 of 4: your building.

Which building is it?

Nissen hut is pre-selected. Change it if yours is different.

Takes about 30 seconds. No contact details yet.

01Why this building

One cold curve, condensation on all of it, and nowhere to fix a board.

A Nissen hut has no purlins, no ceiling and no cavity: the corrugated steel is the roof, the wall and the inside finish all at once. On a cold morning the whole arch is below the dew point of the air inside, so it sweats from floor to floor and drips from the crown. Every conventional lining needs a frame, and the frame takes the space you keep the hut for.

Inside an unlined Nissen hut on a cold morning: condensation running down the corrugated steel arch above stored equipment, daylight from the end wall.
The archBelow the dew point
  • The steel is the finish. There is no cavity to put anything in.
  • The whole curve condenses, not one line of it.
  • Drips fall from the crown onto whatever is stored or worked on beneath.
Roof condensation: what is happening on the sheet Why it forms, when, and what stops it.

02Recent projects

Nissen huts HOLVEM has lined: the curve, in HOLVEM's own photographs.

Arched buildings sprayed from inside by HOLVEM: the whole curve in one continuous layer, with the hut back in use afterwards. Every item carries the label it earns: Project record.

Inside a Nissen hut after treatment: the semicircular arch fully sprayed in a cream closed-cell layer, rooflights along the crown, a person standing on the floor and a scissor lift at the far end.
Project recordThe arch, lined
Nissen hut arch sprayed from insideOne continuous layer over the whole curve, rooflights kept clear.
A finished arched building fully sprayed inside in a cream closed-cell layer, a spray booth installed within it, grey floor and stacked bags.
Project recordBack in use
Arched building lined and back in useClosed cell over the curve; the space fitted out beneath it.

All HOLVEM project records

03What is applied

A continuous layer sprayed to the inside of the curve. No framework, no fixings.

The arch stays as the weather line. Loose paint and rust are removed and the steel is checked for thinning, then the layer is sprayed from inside in passes, following every corrugation from one floor plate over the crown to the other. It bonds to the steel and stiffens it. At 25 to 75 mm the curve you see afterwards is the curve you had, a little softer.

Schematic / not to scaleKeyed 1 to 3 below

Inside a Nissen hut after treatment: the whole arch lined in a continuous cream closed-cell layer that follows every corrugation, the curve intact.
AppliedThe curve, lined
The whole arch in one continuous layer, end wall to end wall. The corrugations still read through it.
1 / Corrugated steel arch

The weather line, and it stays. Its condition is checked before anything is bonded to it; thin or perforated steel is repaired first, by someone else.

2 / Closed-cell layer, following the curve

Sprayed from inside in passes. Bonds to every corrugation, closes the laps and end-wall junctions, and adds bonded stiffness to old steel.

3 / Headroom kept

A framed and boarded lining sits well inside the arch; the sprayed layer takes only its own thickness from the curve.

Corrugated roof underside: the build-up in sequence

04Enverge NexSeal LE

The material we spray, and why it matters.

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.

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.

0.027 W/mKThermal conductivity · aged · BS EN 14315-1
Class 1Surface spread of flame · BS 476-7 · uncoated
B-s2,d0Coated with DC315, as tested · BS EN 13501-1
25 yearsWorkmanship warranty, plus the manufacturer’s

HOLVEM also installs open-cell foam. It is a different product with its own data sheet, specified for different objectives: hybrid build-ups, sound, and where the layer has to breathe. Open-cell system data · Closed-cell system data

HOLVEM spray rig van with Enverge NexSeal LE A and B component drums plumbed into the proportioner.
HOLVEM rigA and B on board
The HOLVEM rig · Enverge NexSeal LE A and B components on board. HOLVEM's own photograph.

05Applications and problems

The elements a Nissen hut puts in front of us, and the problems they bring.

A Nissen hut is one corrugated element with two end walls, sometimes asbestos-cement rather than steel, sometimes with a timber frame added inside. Each has its own application page. The problems below are the ones hut owners ring about.

The elements

The problems

06Depth

Four objectives. Each one sets the depth.

Start with what the building has to do; that decides the depth. Below is what each depth is for on this building. The survey confirms the right one, and the price follows from your area and access, never the other way round.

ObjectiveDepthWhat that depth is for here
Control condensation25 mmStops the arch sweating; nothing lands on what is stored beneath.
Retain heat50 mmHolds heat in a hut that is worked in or lived in.
Reach a calculated U-value75 mm and aboveA figure to meet where a hut is being converted or brought to a calculated standard.
Achieve Euroclass BDepth to suit + DC315 coatingWhere the exposed face needs a reaction-to-fire classification, for example a hut used as a workshop or for public use.

Prices are in the cost guide. A firm figure needs your building, and a coated system is always priced for the project. · Thickness and objective

Want a figure for your building? It takes about a minute.Building, structure, reading, details. A real figure for your building the same working day; nothing sent to anyone else.

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07The survey

Five things we check before anyone talks about depth.

A survey is one visit, from inside the hut, fitted around whatever it holds. Nothing comes off the steel and nothing stops. It gives us the five things a specification for this hut has to stand on.

  1. Condensation, or a leak

    Where the water shows, when it shows and what your photographs say. Condensation and ingress look alike from the floor and need different answers.

  2. The steel’s condition

    Thinning, perforation, loose coatings and rust. The layer bonds to what is there.

  3. End walls and junctions

    Brick, block, timber or sheet, and how the layer closes onto them.

  4. The hut’s use

    Storage, livestock, workshop or occupied. That sets the moisture load and the fire question.

  5. Access

    What has to come out, and whether the work is one visit or two.

What you get after the survey

Five things in writing, whether or not you go ahead.

  • A specificationWritten for this hut, from what we found, with its assumptions named.
  • The depth, and whySet by the objective and confirmed by calculation for the element as built, bridges included.
  • The condensation-risk positionWhether anything will condense inside the build-up, to BS EN ISO 13788 with the BS 5250 climate.
  • The fire positionWhether your fire strategy calls for a classified surface, and the coated or uncoated build-up that answers it. Confirmed against the strategy, never assumed.
  • A firm priceFor your hut, in writing. What moves it is explained in the cost guide.

Survey, or photographs?Send photographs of the hut

A firm figure starts with the building. Yours takes a minute to describe.Building, hut, what you are seeing, and how to reach you. A real figure for your building the same working day; nothing sent to anyone else.

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Project records

Work we have done on buildings like this.

All project records
Project recordA Nissen hut for Rolls-Royce Motor Cars50 mm of closed-cell to the curve, finished with DC315 coating.Read the record Project recordBlack Hangar Studios, AltonA 4000 m² hangar roof made quiet enough to film under.Read the record

08Straight answers

Ask us the hard ones.

The questions Nissen hut owners actually ask on the call, answered the way the specialist answers them. A question we have not answered? Ask it on the call. No obligation.

How much does Nissen hut insulation cost?
It depends on the depth, and the depth depends on what you are trying to fix. 25 mm is the condensation control specification and 50 mm retains useful heat as well. A hut's area is the whole arch, floor to floor, so it is larger than the footprint suggests. Send the hut and we ring you the same working day.
Our hut is old and the steel is thin in places. Is that a problem?
It is the first thing the survey checks. The layer bonds to the steel and adds stiffness, but it does not repair holes or replace perforated sheets: that is done first, by a steel contractor, and then we spray. Where the arch is too far gone, we say so before pricing.
Can the layer be painted or finished?
Yes. The cured surface can take a coating where a finish or a classification is required. The DC315 intumescent coating is the fire route; decorative coatings are agreed case by case, using products compatible with the foam.
What about the end walls?
Brick or block end walls can be sprayed from inside in the same visit so the whole envelope is one layer. Timber or sheet end walls are treated the same way; doors and windows are masked and worked around.
How do you prove it was installed correctly?
Applied thickness checked and recorded around the curve, coverage logged, all compiled into a QA evidence pack handed over at completion. You hold the evidence, not our word.

The next step

Your building.
Your brief.
A specialist.

If you already know the thickness or U-value you need, we price to it and confirm it is right; if not, we work it out with you. Tell us the hut, the steel and what you use it for; the estimator takes about a minute. “Not sure” is a useful starting point.

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Or call . Enquiries received before 3pm on a working day are contacted the same day. After 3pm, the next working day. A commitment to contact, not a quotation, a survey or a price.

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