PUF Porta Cabin with Insulated Sandwich Panel Walls

What a PUF porta cabin actually is

A PUF porta cabin is a transportable building whose walls and roof are factory-made sandwich panels rather than a frame with insulation added inside it. Each panel arrives as one finished element. It carries a pre-coated steel skin outside, a rigid polyurethane foam core in the middle, and a second pre-coated steel skin inside. That inner skin becomes the visible wall surface of the room.

That single sentence carries most of the difference. In a framed and lined cabin, insulation is a layer inside a shell, and the interior finish is a separate material fixed over it. Here the insulation, the weather skin and the interior finish are the same component. The steel structure underneath still does the structural work. Its sizing follows what the chosen panel can span rather than what a cladding sheet needs.

The standard planning build uses 50 mm wall panels and 60 to 80 mm roof panels. Facings are pre-coated GI or GL in the 0.5 to 0.8 mm range that the panel industry typically supplies. We offer an 80 mm wall panel where a project needs higher insulation. The chassis is a 100 x 50 x 3 mm MS C-channel reference frame. The floor sits on an MS cross-grid and uses an 18 mm cement-bonded board, with a 24 mm option for higher duty.

Where the panel build earns its money

Rooms people occupy through the summer

The clearest case is a room somebody sits in all day, in a place that gets genuinely hot. A continuous insulated envelope with sealed joints cuts the heat reaching the inside face. It also cuts the air leakage that makes an air-conditioned cabin expensive to hold at temperature. Site offices, control rooms, testing rooms and any cabin with instruments or people in it for a full shift are the honest applications.

Space that has to look finished immediately

Because the panel inner face is the finished wall, a PUF cabin does not need a lining trade on site. There is no MDF to fit, no joint to fill, no surface to paint before anyone moves in. A cabin delivered on Tuesday can be occupied on Tuesday. For marketing offices, client-facing site offices and anything a visitor will walk into, that matters as much as the thermal performance.

Interiors that need a wipeable surface

The pre-coated steel inner face is a hard, smooth, cleanable surface. That suits rooms where dust, handling or hygiene expectations make a soft lining a liability. This is not a clean-room specification and we do not claim one. The base surface simply starts from a better place than a board lining.

The envelope, layer by layer

Wall panels: 50 mm standard, 80 mm option

Fifty millimetres is the standard planning thickness. The published price ladder costs against this thickness, and it suits most site offices in most Indian conditions. Eighty millimetres is the documented higher-insulation option. Specify it when the cabin faces long solar exposure, when air-conditioning load drives your operating cost, or when the room must hold temperature with plant running outside.

Thickness is a planning decision, not a performance certificate. Core density and thermal conductivity come from the panel supplier's certificate for the system you actually buy, and the purchase order names them. We publish no conductivity figure or U-value for the cabin. A cabin figure would have to account for the frame, the joints, the openings and the installation, and none of that is fixed until the design is.

Roof panels: why the range is 60 to 80 mm

The roof gets more thickness than the walls for a simple reason. It takes the most direct solar gain, it spans further, and it has to carry drainage and any service loads. The factory roof panel gives you weather skin, insulation and finished underside in one element. Its outer skin is profiled and its inner liner arrives finished.

Where the roof lands inside the 60 to 80 mm range depends on heat gain, on the span the design needs, and on condensation requirements. The panel supplier's structural and thermal data governs the allowable span and the fastener spacing. We therefore coordinate the roof secondary members to the panel rather than assume them. These are typically 50 x 50 x 1.2 mm and engineered as the span requires.

Facings, joints and why sealing decides the result

A good panel installed with poor joints performs like a poor panel. The controls that matter are unglamorous. We use interlocking joint profiles, corrosion-compatible mechanical fasteners, EPDM or butyl or approved sealants, and flashings at joints, corners, roof laps and every penetration.

We accept no unsealed field cut. Every cut edge exposes the core, and an exposed core is where water, vapour and time get in. Where a cut has to happen, we close it with the approved flashing and sealant detail before the panel passes inspection.

The steel under the panels

It is worth being explicit about this, because the panel is the visible part and it is easy to assume it does everything. It does not. The transport and lifting chassis remains structural steel, and we size it independently for cabin loads and for handling. Panel fasteners never substitute for structural connections.

The reference build uses a 100 x 50 x 3 mm MS C-channel bottom frame. Stiffeners in 100 x 50 and 75 x 40 channel and square pipe support the floor loads and the panel perimeter rails. A 50 x 50 x 1.6 mm MS SHS top frame gives the wall panel heads a straight, level bearing. Wall framing is 50 x 50 x 2 mm MS SHS, with framed openings locally reinforced.

That last point has a practical consequence. Large openings need local reinforcement, and we design that reinforcement in rather than cut or crush the panel core to get it. A wide window or a double door is a structural decision taken before manufacture, not an adjustment made later.

Lifting and handling points are engineered provisions. We move a completed module only to the approved lifting, support and transport drawing. We weld or bolt structural connections to approved shop drawings, deburr and inspect edges, and close panels only after the frame passes inspection.

Services: planned before manufacture, never cut in later

This is the single discipline that separates a PUF cabin that lasts from one that disappoints, and it is the thing most buyers are never told.

You cannot route services by cutting channels through a sandwich panel. Doing so removes core, breaks the vapour path and leaves an unsealed edge inside the wall where nobody will ever see it fail. So we settle the service strategy before the panels are made.

In practice that means:

• Wiring runs in planned chases and raceways, or in surface containment, rather than in improvised cuts.
• Copper wiring follows the standard starting schedule: 1.5 sq.mm for lighting, 2.5 sq.mm for sockets, 4 sq.mm for higher-load or air-conditioning circuits. The load schedule and the approved electrical drawing set the final sizes.
• We provide a distribution board with MCB and RCCB protection, earthing, and segregation of lighting, socket, wet-area and air-conditioning circuits, to the approved drawing.
• Plumbing, where you order it at all, uses factory-planned sleeves and chases. We seal every penetration and protect the core, and we plan service zones and removable covers before manufacture.
• We plan air-conditioning sleeves and condensate drains at the factory, so we restore insulation and vapour sealing around each penetration rather than patch it later.

Final quantities of lights, switches, sockets, fan points and air-conditioning provision stay quotation-specific, and we coordinate them with the approved layout. We do not publish fixed counts, because a count that is right for one layout is wrong for the next.

Condensation, ventilation and air conditioning

An insulated, well-sealed box behaves differently from a leaky one, and that is mostly the point. It also means the ventilation strategy has to be chosen deliberately rather than left to the gaps.

We select the ventilation approach for occupancy and climate. It may use natural ventilation through the opening schedule, or air conditioning with controlled condensate. What it must not be is uncontrolled vapour movement through panel joints, because that is how moisture reaches places it cannot dry from.

Where a false or service ceiling is added below the insulated roof, it creates a void for services. It does not replace the roof panel's thermal function, and the vapour and condensation control has to stay continuous above it. That distinction is easy to lose on site and expensive to rediscover later.

What a PUF panel does not do

Two limits deserve stating plainly, because the market around this product is not always honest about them.

The first is fire. Fire resistance cannot be inferred from PUF thickness. A thicker PUF panel is a better insulator; it is not a fire rating. Where a project requires a non-combustible core, the answer is a tested mineral-wool panel system rather than more polyurethane. That is a different build with a different specification. If fire performance is what your project is actually buying, start at the fire-rated porta cabin instead of specifying this one and hoping.

The second is that a panel is not a structure. The chassis carries the building. The panel closes it, insulates it and finishes it. Treat with suspicion any claim that a sandwich panel cabin needs less steel because the panels are strong.

Choosing between 50 mm and 80 mm

The honest guidance is narrower than most buyers expect.

Specify 50 mm for a normal site office in normal conditions. It suits cabins where air conditioning runs during working hours rather than continuously, and cabins you expect to relocate within a few years. This is the standard build, and the published prices cover it.

Specify 80 mm where solar exposure runs long and unshaded, or where the room must hold a set temperature against a continuous heat load. It also earns its cost when air-conditioning running cost over a multi-year deployment is a real line in your budget, and on semi-permanent cabins.

Specify neither on the basis of a number you found on a competitor's page. Panel data belongs to the panel you actually buy, and the supplier issues it as a certificate against that purchase order.

Standard, optional, custom and excluded

We publish this table because the most common source of dispute on a modular building is not the price. It is the boundary between what arrived and what somebody assumed would arrive.

Six sizes and published prices

These are derived planning estimates, and we confirm the panel system at quotation. The rate falls as the footprint grows because the envelope, the openings and the services scale with perimeter rather than with floor area. Interior fit-out, optional add-ons, transport, installation, foundations and any project-specific engineering or testing sit outside these figures. The wider porta cabins range covers the other configurations in this cluster if the insulated build is not what your site needs.

If you want the panels on their own rather than a finished cabin, we supply PUF panels separately and price them by thickness.

Site readiness and handover

A PUF cabin asks for the same site preparation as any other module in the range, with two additions worth planning for.

Prepare a level, load-bearing base with drainage away from the cabin footprint. Pedestal or plinth support at the designed positions matters more here than on a framed cabin. A module that sits out of level puts the panel joints out of line, and joints out of line do not seal as designed.

Keep the panel faces protected during offloading and positioning. A pre-coated skin is the finished surface, so a gouge is not a scratch on a cladding sheet, it is damage to the finished wall. Touch-up is possible, and we match the corrosion protection system to substrate and exposure, but prevention costs nothing.

Pre-dispatch quality checks cover dimensions, member and panel identification, connections, coating, roof drainage, weather sealing, doors, windows, electrical continuity and functional checks. We verify specialist performance certificates where the product requires them.

The final quotation confirms warranty period and exclusions. Relocation damage, misuse, site services, consumables and unapproved alterations sit outside the agreed scope unless the quotation explicitly includes them.

What we need to quote accurately

A PUF cabin quotation moves faster when these are settled at enquiry:

• Footprint and quantity, and whether the cabin is a standalone module or part of a linked set.
• Wall panel thickness, 50 mm or 80 mm, and whether the roof sits at 60 mm or 80 mm.
• Any nominated panel system or brand, or confirmation that we may propose one.
• Opening schedule: door type and position, window sizes and positions, and any framed structural opening.
• Service requirements: lighting and socket layout, air-conditioning provision and sleeve positions, and whether plumbing is in scope.
• Floor duty, so we can confirm 18 mm or 24 mm base and the finish.
• Site access, approach width, offloading arrangement and the delivery location for freight.
• Colour and coating preference, and whether the cabin is a short deployment or semi-permanent.

Anything we cannot confirm from that list stays a quotation input rather than a website claim.

Questions buyers actually ask

Is a PUF cabin cooler than a standard site office? A continuous insulated envelope with sealed joints reduces heat transfer and air leakage, and buyers report that as a more comfortable room. We publish no temperature difference. The honest answer depends on orientation, glazing, ventilation, occupancy and the air-conditioning system, and the design fixes none of those until it is complete.

Can I get a U-value or a thermal conductivity figure? For the panel you actually buy, yes, from the supplier's certificate, and the purchase order names it. For the finished cabin as an assembly, that needs a defined calculation or test method covering the frame, joints and openings. We quote a cabin figure only against such a method.

Is PUF fire resistant? No, not by virtue of being PUF, and not more so because it is thicker. Where a project requires a non-combustible core, a tested mineral-wool panel system replaces PUF.

Can I cut a new opening after delivery? Not without a designed detail. We protect the core, then seal and flash the cut edge, and larger openings need local reinforcement. Tell us at enquiry if a future opening is likely.

Does the interior need painting? No. The panel inner face is the finished surface. A decorative or hygienic lining is a separate order if you want one.

Is the 80 mm option worth it? It is worth it for long solar exposure, continuous temperature holding, or a multi-year deployment where air-conditioning running cost matters. For a normal site office on a normal programme, 50 mm is the specification we would recommend.