Guides / Modular Buildings
A detachable container house is bolted together on site, not welded. The frame is hot-dip galvanised steel with bolted detachable connections, the panels are sandwich panels that fix into that frame, and the whole thing arrives flat-packed: four sets in a 20 ft container, eight in a 40 HQ for the standard unit. So the installation question is not “who can weld it” but “is the base, the lift, the drawing and the crew ready on the day the container is opened”. This page takes those four in order, then the services connection, and finishes with the checklist worth having on site.
A detachable container house is installed in four operations: a level drained base, a lift of the frame sections onto it, a bolt-up in the sequence on the drawing, and the panels fixed into the frame with the services connected. No site welding is involved in the structure, so no welder and no hot work permit are needed for it. What the job does need is a base built before the container arrives, lifting equipment chosen on the unit weight at the working radius, and the assembly drawing on site rather than in an email inbox.
The failure mode is almost never the assembly itself. It is a base that was poured two days late, a crane that was booked for the wrong day, or panels standing in the wind because the frame was not bolted up yet.
On our own detachable container house page the order runs in five steps, and only the last one happens on the buyer's site. That split matters, because it means the site programme starts on the day the container lands, not on the day the order is placed.
Because the unit travels as a kit, the buyer's site work is assembly and not construction: there is no concrete pour inside the scope, no structural steel erection in the conventional sense, and no wet trades beyond making the services connection good.
The base does three jobs: it carries the unit, it holds the frame in one plane, and it keeps water away from the floor. On our standard build the floor is a cement fibre board over a steel joist, so standing water under the unit is a floor problem within a season, not a cosmetic one.
Footings are designed against the ground conditions under EN 1997-1, the geotechnical part of the Eurocodes, and the two inputs to that design are the unit weight and the imposed floor load. Both come from the supplier for the specific unit, and both should be requested with the quotation rather than assumed. What the base is made of is a local decision: cast-in-situ pad or strip footings, precast blocks, or screw piles. On a site with a defined service life, screw piles come out again; on a site that will be built over, a slab may be the cheaper choice even though it is heavier work.
Level is the part buyers underestimate. A bolted modular frame does not absorb an out-of-level base the way a site-built frame can: it shows up as doors that will not close cleanly, windows out of square, and panel joints that will not pull up. Ask the supplier for the level tolerance the frame is set out to, and check the base against it with a level and a string line across both diagonals of each footprint before the container is opened. Fixing a base is a day. Fixing it after the units are bolted is a week.
| Unit | External size | Footprint |
|---|---|---|
| 20 ft standard | 6058 × 2438 × 2591 mm | 14.77 m² |
| 40 ft | 12192 × 2438 × 2591 mm | 29.72 m² |
Sizes are the standard build on our product page; custom sizes are available and change the base. The footprint column is the external size multiplied out, not a usable floor area: internal area is smaller by the wall thickness.
Two more base items belong in the same conversation. The first is anchoring: wind action is calculated under EN 1991-1-4, and on an exposed site the uplift on a lightweight unit is what the anchors are resisting, so the base design has to know what the anchors are going into. The second is drainage fall: the base should fall away from the unit, not towards it, and the roof downpipe outlet should be able to reach the ground without crossing the access side.
Nothing about the delivery is one heavy box. The unit arrives flat-packed, so what gets lifted on site is frame sections and bundles of panels, and that changes the equipment question completely.
A crane is not automatically required. A telehandler with forks will place frame sections and panel bundles where the ground is firm and the reach is short, and it is usually the cheaper route on a site that already has one. A crane earns its cost where the unit has to go over an obstruction, beyond the reach of a telehandler, or into a tight yard. The decision is made on the load chart at the actual working radius, using the unit weight from the packing list: a chart figure for the machine's nominal capacity says nothing about what it can pick up at eight metres.
Handling practice for the container itself follows ISO 3874, which covers the handling and securing of series 1 freight containers, and it is the reason a container is lifted at its corner fittings and never slung under its floor. For a bolted frame the equivalent rule is that the lifting points are the ones shown on the assembly drawing, and no panel edge, purlin or roof sheet is a lifting point whatever it looks like.
The frame is hot-dip galvanised steel with bolted detachable connections. Galvanising for structural steel is specified under ASTM A123 or EN ISO 1461 depending on the market, and the practical consequence on site is that the coating is the corrosion protection: a member that gets drilled or cut for a site change has a bare edge until it is repaired with a zinc-rich product, and that repair belongs in the same day's work.
The sequence on the drawing is not a suggestion. A partly bolted frame has very little stiffness, so the order in which the frame is closed up decides whether the unit comes out square.
One sequencing rule covers most of the risk on a small site: do not leave a unit half-panelled and unbraced overnight in wind. Either close the envelope or leave the frame in a state the drawing calls stable.
The unit arrives with its internal electrics installed: surface conduit, sockets and switches per the unit layout, and a bathroom pod with pre-fitted plumbing where one is specified. What stays on site is the connection from the unit to the site's own networks, and that is local work done to local rules.
We supply the unit's internal services and the drawings for the connection; we do not sign the local electrical certificate, and no supplier outside the country can.
Everything on this list can be done while the unit is on the water. Everything left undone becomes a delay with a crew standing on it.
| Item | Ready when | Why it matters |
|---|---|---|
| Base | Built, level to the supplier's tolerance, draining away from the footprint, anchors in place | The frame cannot be pulled square on an out-of-level base, and re-doing it after bolt-up is demolition work |
| Lifting equipment | Booked for the delivery date, load chart checked against the unit weight at the working radius | The most common single day lost on an installation |
| Drawings and packing list | Printed and on site, assembly drawing plus bolt schedule plus panel layout | The sequence and the torque values are on the drawing, not in an email |
| Tools | Impact driver, torque wrench, level, string line, sealant gun, zinc-rich repair aerosol | One missing tool stops a whole operation, and the repair aerosol is the one always forgotten |
| Crew | Agreed size, briefed on the sequence, fall protection available if anyone works at height | Under OSHA 29 CFR 1926.501(b)(1) fall protection is required from 6 ft (1.8 m) above a lower level; local rules differ, the principle does not |
| Power and water at the boundary | Available, with the connection point agreed | Commissioning cannot start without them, and it is on the critical path at the end |
| Storage and weather | Panel bundles stored flat, off the ground, weighted or strapped against wind | A panel bundle is a sail, and damaged panels are a re-order with a sea freight lead time |
| Permits and inspection | Booked if the project requires one, before work starts | An inspector who arrives to a closed envelope and no records is a second visit |
Six items, all of which are documents rather than opinions, and all of which should arrive with the quotation or the order confirmation:
How those documents are checked before dispatch is described on our inspection page, and the ones a project can request as a package are listed under certifications.
This page covers the site work. The dimensions the base and the lift are worked out from are on the container house size guide, which separates the external envelope from the internal clear size and the wall build-up between them. The cost side, including what a quote usually leaves out such as foundation, crane hire and clearance, is on the container house cost guide.
If the project is a flat-pack or expandable unit rather than a standard detachable, the fixing sequence is different and the flat-pack and expandable range carries the details. Send the site plan, the unit count and the destination, and the reply comes back with the loading plan, the weight and the assembly drawing. Send drawings and the destination, or use the contact page.
It needs lifting equipment, but not necessarily a crane. The frame is delivered flat-packed, so the loads on site are frame sections and panels rather than a finished room, and a telehandler with forks can handle them where the ground and access allow. A crane is quicker where the unit has to be placed beyond the reach of a telehandler, or where the site is tight. Either way the choice is made on the load chart at the actual radius, using the unit weight from the packing list, not on a nominal tonnage.
Yes, and that is the point of the detachable design. Panels bolt to a hot-dip galvanised steel frame through bolted detachable connections, with no site welding on the structure. No welding means no welder, no hot work permit for the structure, no fire watch and no site-applied paint over a weld. Where a galvanised member has to be cut or drilled on site, the cut edge is repaired with a zinc-rich product according to the coating standard rather than left bare.
A base that carries the load, keeps the frame in one plane and drains water away from the floor. In practice that is cast-in-situ pad or strip footings, precast blocks, or screw piles, chosen against the ground conditions under EN 1997-1. The two numbers the base design needs are the unit weight and the imposed floor load, both of which come from the supplier for the specific unit, and neither of which should be guessed from the product name. A slab is convenient but it is not the only option, and on a temporary site it is often the wrong one.
It depends on the unit count, the fit-out level, the crew size and how much of the work is panel fixing against how much is services connection, so a single figure quoted without those four would be a guess. What can be asked for, and should be, is a crew-and-hours schedule per unit from the supplier: how many people, how many hours per unit for frame, envelope and fit-out separately, and which of those operations assume a crane on site. That schedule is what a local contractor prices against.
Local labour can do it, and most export orders are assembled that way, provided the assembly drawing, the packing list and the bolt schedule are on site and someone on the crew can read a drawing. The risk is not skill, it is sequence: a bolted frame that is half assembled is not braced, and a roof sheet fixed before the fall of the single-slope roof has been checked against the drawing has to come off again. If the crew has not built one before, a supplier supervisor for the first unit is usually cheaper than the rework.
Yes. Two units can be bolted together along a shared side to make a larger floor area, which is how a canteen or a classroom is usually built from standard units. The joint is a line of bolts between the two frames, and both floors have to be at the same level before the joint is closed, so the base under a twin unit is one base set out for both footprints, not two bases built independently. Anything beyond a side-by-side joint, such as stacking, is a structural question that has to be answered by the frame design for that project.
The base, built and level and draining away from the unit; the lifting equipment, booked with its load chart checked against the unit weight; the assembly drawing and the packing list; a crew with an impact driver, a torque wrench, a level, a string line and sealant; power and water available at the boundary for the services connection; and the local inspection booked if the project needs one. Opening a container of panels onto an unprepared site is how panels get damaged and fixings go missing.
The footprint figures in the table above are the published external sizes multiplied out, and can be recomputed from the dimensions printed beside them. No assembly hours, crew size or lifting capacity is published on this page: those follow the unit count, the fit-out and the machine, and a number written without them would be out of date before the container sailed.