# Modular Construction – The Essential Guide For Architects > A complete guide to modular construction for architects: design rules, module sizes, transport limits, factory coordination, site install and costs. - URL: https://essential.construction/academy/tutorials/modular-construction-2/ - Author: Kyle Parry (https://essential.construction/about-us/kyle-parry/, https://www.linkedin.com/in/kyleparry/) - Kyle Parry is the founder of Essential Construction. He has worked in construction for more than 20 years, leading projects across Canada for the country's largest contractors and developers. - Publisher: Essential Construction (https://essential.construction/) - Last updated: 2026-11-04 --- [**Modular construction**](https://essential.construction/academy/glossary/modular-construction/) is a building method in which large parts of a building, either complete three-dimensional modules or flat panels and sub-assemblies, are manufactured in a factory, shipped to site and assembled on foundations that were built while the factory work was under way. The overlap between factory production and site work is what makes the method faster, and committing to it early is what makes it work. This guide is written for the architects, project managers and site supervisors who have to make a modular project succeed. It covers the main types of modular construction, how modules are made, the real advantages and limitations, how modular compares with site-built work, and the decisions each phase demands, from predesign and manufacturer selection through design freeze, transport and setting modules on site. ### Table of Contents - What Is Modular Construction? - Types of Modular Construction - How Modules Are Built in the Factory - Advantages of Modular Construction - Disadvantages and Limitations of Modular Construction - Modular vs. Traditional Construction - When Is Modular Construction a Good Fit? - The Modular Construction Process Step by Step - Predesign: Decisions to Make Before Schematic Design - Design Phase: Working With the Manufacturer - Construction Phase: Factory, Transport and Set - Modular Construction Examples - The Modular Construction Market Today - Frequently Asked Questions About Modular Construction - Related Templates and Guides ## What Is Modular Construction? In a conventional project almost every trade works in sequence on the site: foundations first, then the frame, the envelope, services and finishes. In a modular project a large share of that work moves indoors. A manufacturer builds sections of the building on a production line or in fixed bays, fits them out to an agreed level, inspects them and trucks them to site, where a crane sets them on a foundation or podium that the site team has been building at the same time. Modular construction is one branch of **off-site construction**, which also covers precast concrete, prefabricated MEP racks and similar components. Here "modular" means a building, or a large part of one, delivered as factory-made modules or panels designed as a system from the start. It is also worth being precise about what modular is not. In the United States, a **manufactured home** is built on a permanent chassis to the federal HUD Code. A permanent modular building is designed and approved to the same state and local building codes as any site-built building, usually based on the International Building Code (IBC) or International Residential Code. The two products look similar on the back of a truck but sit under completely different regulatory systems. ### A short history Factory-made buildings are not new: kit houses were shipped to California during the 1849 Gold Rush, and prefabricated housing filled gaps after both world wars before spreading to schools, clinics and hotels from the late 1950s. What has changed is the technology. BIM, CNC machining and better connection details now make mid-rise and even high-rise modular buildings practical, with architecture that no longer reads as "temporary". ## Types of Modular Construction Modular systems are usually grouped by what leaves the factory. The two basic families are volumetric (three-dimensional boxes) and non-volumetric (flat or linear components). Most real projects mix them, and also mix in conventional site-built work where it makes more sense. ### Volumetric modules A volumetric module is an enclosed box of space with its own floor, walls and ceiling. Modules can be shipped as bare structure or almost complete, with windows, plumbing, wiring, kitchens and finishes installed. One apartment or hotel room may be a single module or two or three modules joined on site. Because the boxes stack, volumetric construction suits buildings made of many similar rooms: hotels, student housing, apartments, senior living, prisons, clinics and classrooms. Volumetric modules can be **load-bearing**, so that the stacked boxes form the structure of the building, or **non-load-bearing**, so that they are slotted into a separate steel or concrete frame. The choice changes who designs the structure (see the design section below) and how tall the building can go. ### Panelized and other non-volumetric systems Non-volumetric systems send flat or linear components to site: load-bearing wall panels, curtain wall and cladding units, floor cassettes, hollow-core planks, roof trusses, and prefabricated frames, beams or columns. They pack more efficiently on a truck than boxes of air, which cuts freight cost, but they need more on-site labour to assemble, seal and finish. Panelized systems are common in single-family and low-rise housing and in envelope packages for larger buildings. ![volumetric vs non volumetric modular construction](https://essential.construction/academy/wp-content/uploads/sites/22/2023/04/image.png) ### Pods and core units Between full modules and flat panels sit pods: complete bathrooms, kitchens, plant rooms or sections of stair and elevator cores, built in a factory and set into an otherwise conventional or panelized building. Bathroom pods are the best-known example because bathrooms pack many trades into a small space, which is where site productivity is lowest. Our library has a white paper on [saving time with modular bathroom pods](https://essential.construction/files/information/white-papers/saving-time-with-modular-bathroom-pods/). ### Permanent and relocatable modular **Permanent modular construction (PMC)** produces buildings that stay where they are set, meet the same codes as site-built work and are financed and insured like any other building. **Relocatable** buildings, such as site offices, portable classrooms and emergency or transitional housing, are designed to be moved and reused, often on simple above-grade foundations. Both rely on the same factory methods; the difference is in design life, approvals and how the building is attached to the ground. ### Frame materials and construction types Modules are built in light-gauge steel, hot-rolled structural steel, wood or precast and cast-in-place concrete. Wood-frame modules dominate low-rise housing, while steel is preferred as buildings get taller and where non-combustible construction is required. Modular buildings can satisfy any IBC construction type, and because many manufacturers work in only one material, the choice narrows the supplier list early. In practice most projects fall into Type II (non-combustible) or Type V (combustible) construction, which is where the manufacturing process is simplest. ### Modular construction types compared | Type | What leaves the factory | Typical uses | Main trade-off | | --- | --- | --- | --- | | Permanent volumetric | Complete 3D modules, often with MEP and finishes installed | Apartments, hotels, student housing, healthcare, schools | Highest share of work off-site; module size limited by transport | | Relocatable modular | Complete modules designed to be moved and reused | Site offices, temporary classrooms, emergency and transitional housing | Fast and reusable, but simpler design and shorter design life | | Panelized (non-volumetric) | Wall panels, floor cassettes, roof trusses, facade units | Single-family and low-rise housing, envelope packages | Cheaper to ship; more site labour to assemble and seal | | Pods and core units | Bathroom and kitchen pods, plant rooms, core sections | Hotels, residential towers, hospitals | Captures factory quality for the most trade-dense rooms only | | Hybrid | A mix of modules, panels, pods and site-built elements | Projects with large spans or unique spaces alongside repetitive rooms | Most flexible; interfaces between systems need careful detailing | ## How Modules Are Built in the Factory Designers and site teams do not need to run a plant, but they must understand it well enough to design and plan around it. Three things matter most. **The build sequence is reversed.** On site, a building is generally closed in from the outside before the interior is finished. A volumetric module is often built the other way round: the floor and wall frames are assembled, interior linings and finishes go on, services and insulation are installed, and the outer sheathing and cladding come last. The order varies between plants, which is one reason to visit the factory before the design is fixed. **Production is organised as a line or as stations.** Some plants move modules along a linear line, with each crew doing its task at a fixed station before the module moves on. Others keep modules in static bays and bring the trades to them, so several crews can work on one module at once. The method affects how much variety a plant can absorb without slowing down, and how quickly it can recover from a design change. **Digital data drives the shop floor.** Modular plants rely on BIM and CAD models that feed computer-aided manufacturing (CAM) and CNC saws, routers and steel-framing machines. That chain is what allows *mass customisation*: a limited set of standard parts and processes can be combined into many different layouts and finishes without the cost of one-off fabrication. The underlying discipline is **Design for Manufacture and Assembly (DfMA)**: designing the building as a product whose parts are easy to make, move and assemble. ## Advantages of Modular Construction Moving work into a factory creates the conditions for these benefits, not the benefits themselves. They are real on well-run projects and can disappear on poorly planned ones. ### Shorter, more predictable schedules The headline benefit is time. While the site team excavates, pours foundations and brings in utilities, the factory is building the superstructure. The Modular Building Institute (MBI) cites schedule reductions of 30 to 50 percent compared with site-built construction when this parallel working is properly coordinated. Treat that range as an industry rule of thumb rather than a guarantee: the research MBI draws on modelled scenarios rather than measuring a single average. Factory work is also largely immune to weather, and trades can work on different modules at once instead of waiting for each other floor by floor. Highly customised projects gain less, because unique modules take longer to engineer, build and set. ### Quality and consistency A factory offers fixed jigs, calibrated tools, a stable workforce and inspection at set points on the line. That means tighter tolerances and fewer defects, especially in work that is hard to do well outdoors, such as air-sealing and fire-stopping. Materials stay dry, reducing the risk of moisture damage and mould. ### Safety Factory crews work at ground level or on fixed platforms, away from traffic, weather and most work at height. That matters because construction remains one of the more dangerous industries: in its 2023 Census of Fatal Occupational Injuries, the U.S. Bureau of Labor Statistics recorded 9.6 deaths per 100,000 full-time-equivalent construction workers, against 3.5 across all industries. Crane lifts and work at module edges remain high-hazard, but a large share of labour hours moves to a controlled setting. ### Cost certainty Modular construction is not automatically cheaper, but its costs are usually more predictable. Much of the price is fixed in a factory contract, there are fewer weather and productivity surprises, and a shorter programme cuts site overheads, interest and the time before the owner earns revenue. KPMG's 2016 *Smart Construction* report on off-site manufacturing in the UK estimated net financial savings of around 7 percent on one-off projects, driven by the shorter construction period rather than by cheaper building work. ### Less waste and lower environmental impact Factories cut materials to order and reuse or recycle offcuts, so far less waste goes to landfill, and fewer worker trips and small deliveries cut transport emissions. Precise envelope assemblies with fewer site-made joints make high airtightness targets, such as Passive House, more achievable. ### Smaller site footprint and less disruption With most work done elsewhere, the site needs less laydown space, fewer workers and fewer deliveries, and the noisy phase is much shorter, which is valuable on tight urban sites and next to occupied hospitals, schools and campuses. ### Adaptability and reuse Bolted-together modules can be designed to be extended, reconfigured or moved, and even if they are never reused, a building designed for disassembly comes down more cleanly than one that must be demolished. ## Disadvantages and Limitations of Modular Construction Modular construction is a tool, not a default. Most of its limitations can be managed if they are recognised before the team commits. ### Decisions have to be made much earlier On a site-built project, interior layouts and details often keep developing while the frame goes up. On a modular project that is not possible: once modules are in production, every change is expensive and may stop the line. Layouts, service routes, finishes and connection details must be resolved before fabrication, and owners have to accept that late changes carry a high price. ### Transport and lifting limits Every module has to fit on a truck, pass under bridges and around corners, and be lifted by a crane that can reach its final position. On U.S. federal-aid highways the standard legal vehicle width is 102 inches (8 ft 6 in), so most volumetric modules travel as oversize loads with state permits, set routes and sometimes escorts. These limits govern module size and therefore room layouts. ### Bulkier floors and walls Each volumetric module carries its own floor, ceiling and walls, so adjoining modules create double walls and deeper floor-ceiling zones than a site-built frame. That helps with acoustic separation and fire compartmentation, but it eats into floor area and adds height, which can cost a storey on a height-limited site. Very large clear spans and tall open volumes, such as a big-box store, do not suit volumetric modules. ### Approvals that are unfamiliar to the team Modular buildings follow the same codes as site-built ones, but the route to approval is different: plan review and inspection of the factory work may sit with a state program or third-party agency, while the site work stays with the local building department. Where officials or the project team have little modular experience, that split can add time. ### Financing, payment and procurement Lenders and public owners usually pay monthly against work in place on site. On a modular project much of the value is created in a distant factory, and banks may treat finished modules as stored materials. Factory deposits, up-front engineering and certification of off-site progress must be agreed before signing, and some public procurement rules make that difficult. ### A thinner supply chain Many manufacturers focus on specific building types and on low- to mid-rise work, and the most capable plants are often booked months ahead. A project depends heavily on one supplier, so the manufacturer's financial health and capacity are a real project risk. There can also be resistance from site trades and unions, since more of the labour moves into the factory. ### When modular may not pay off The advantages shrink on sites with easy access, cheap land, a long building season and affordable labour, where a well-run site-built project may match modular on time and cost. Lower waste and shorter disruption may still tip the balance. ## Modular vs. Traditional Construction The table compares a typical volumetric modular project with a conventional site-built one. Real results depend on the design, the manufacturer and how early the team commits. | Factor | Modular construction | Traditional site-built construction | | --- | --- | --- | | Where the work happens | Most of the building is made in a factory; for volumetric projects NIBS's Off-Site Construction Council puts the share as high as 95 percent | Almost all work is done on site | | Programme | Factory production and site work overlap; MBI cites 30 to 50 percent shorter schedules | Sequential: foundations, frame, envelope, then fit-out | | Weather risk | Low; modules are built and stored indoors | High; delays and moisture damage are common | | Design changes | Must stop at a design freeze before production | Can continue, at a cost, during construction | | Cost | More predictable, not automatically lower; transport, cranage and engineering add cost | More exposed to labour, weather and change-order costs | | Quality control | Factory inspection, repeatable processes, tight tolerances | Depends on site supervision and trade skill | | Site impact | Smaller laydown, fewer workers and deliveries, but large crane lifts | Larger laydown and longer disruption to neighbours | | Best suited to | Repetitive rooms, tight or remote sites, short build seasons, scarce or costly labour | Unique forms, long spans, easy sites with affordable labour | ## When Is Modular Construction a Good Fit? Before anyone draws a module grid, test the project against these questions. The more "yes" answers, the stronger the case. - Is early occupancy or revenue worth real money to the owner? - Does the building contain many repeated rooms or bays, such as hotel rooms, apartments, classrooms, patient rooms or labs? - Can the structure work with moderate spans and fairly dense framing? - Is the site hard to work on, because it is urban and cramped, remote, in a short building season, or next to sensitive neighbours? - Are skilled trades scarce or expensive in the area? - Is there at least one suitable, approved manufacturer within shipping distance? - Are the owner and lender prepared for a different payment profile and an early design freeze? A project that scores poorly can still use pods, panelized walls or prefabricated MEP racks in a hybrid approach; modular is not all or nothing. Modular also changes professional roles. Some work that used to be "means and methods" for the contractor, such as module splits, lifting points and delivery sequence, becomes part of the design, and the manufacturer may take over the structural design. Architects should confirm the scope of their services, and check with their insurer and legal adviser, before agreeing to a modular commission. ## The Modular Construction Process Step by Step The following sections cover each phase in detail. In summary, a typical volumetric project runs like this: 1. **Test feasibility and commit.** Check repetition, site, schedule and labour market, and decide on modular before design development starts. 2. **Choose a collaborative delivery model.** Design-build or integrated project delivery (IPD) brings the manufacturer in early (see our guide to [construction contract types](https://essential.construction/academy/tutorials/common-types-of-construction-contracts-and-their-use/)). 3. **Prequalify and engage a manufacturer.** Check experience, capacity, distance to site, state approvals and licences. 4. **Design with the manufacturer.** Develop the module key plan, structure, connections, mate-line details, service routes and transport envelope together. 5. **Obtain approvals.** Submit module drawings to the state program or local authority and agree where inspections will happen. 6. **Freeze the design.** Lock the design and order long-lead materials before production. 7. **Build in parallel.** The factory produces and inspects modules while the site team builds foundations, utilities and any site-built cores. 8. **Ship and stage.** Secure permits, routes and escorts, and plan either just-in-time delivery or a staging yard. 9. **Set and connect.** Lift modules into place under an engineered [crane lift plan](https://essential.construction/academy/tutorials/how-to-plan-your-next-construction-crane-lift/), tie them together and to the foundation, and close the mate lines. 10. **Finish and hand over.** Complete cladding, mate-line finishes, service connections, inspections and commissioning. ## Predesign: Decisions to Make Before Schematic Design ### Commit to modular from the start A building designed for site construction and then chopped into boxes rarely captures the benefits of modular, and often costs more. Module size, structural grid, service routing and transport all shape the plan, so the decision has to be made before or during concept design and certainly before design development. For teams new to the method, bringing a manufacturer in by the schematic concept stage is the most useful single step. Our guide to [preconstruction planning](https://essential.construction/academy/tutorials/the-ultimate-guide-to-preconstruction-planning/) covers the wider set of early decisions. ### Pick a delivery model that allows early collaboration Traditional design-bid-build keeps the builder out of the room until the design is finished. By then, optimising the design for a particular manufacturer means redesigning it, and the linear hand-offs between parties tend to stretch the programme. Collaborative models suit modular much better. In **design-build**, the designer, contractor and manufacturer develop the design together, the manufacturer can explain production and transport limits from day one, and real costs are known early enough to steer the design. **Integrated project delivery** goes further, with shared risk and reward among the owner, designer, builder and key trade partners including the manufacturer. Construction manager at risk with early manufacturer engagement can also work. Whatever the model, involve both the manufacturer (off-site work) and the construction manager or general contractor (site work) early. Sometimes one company does both. ### Allocate risk, insurance and financing Agree in writing who owns each module, and who carries the risk, at each stage: in production, in storage, on the truck, in the staging yard and once set. Settle early: - **Transport risk.** Delivery is usually in the manufacturer's contract, so the manufacturer should confirm that the carrier's cover is adequate. Transport damage is uncommon and is usually repaired on site. - **Builder's risk.** Standard policies may not cover finished modules stored away from the site, for example if the site is late. An endorsement may be needed. - **Wrap-up programmes.** Owner- or contractor-controlled insurance programmes (OCIP/CCIP) are built around site payroll, and may fit poorly when most labour is in a factory. Confirm with the broker. - **Workers' compensation.** NCCI uses separate classifications for factory work (code 2797, modular building manufacturing, shop work) and for site set-up and installation (code 2799). Some states use their own systems, so check locally. - **Lending.** Lenders may treat finished modules as materials rather than work in place. Agree how factory progress will be certified and paid for, including deposits, before the loan closes. A shorter programme also changes cash flow: interest is paid for fewer months and income starts sooner, so financing should be modelled on the modular schedule rather than a conventional one. Our guide on [managing construction project risk](https://essential.construction/academy/tutorials/construction-project-risk/) has a framework for the rest of the risk register. ### Understand codes, approvals and inspections A permanent modular building must meet the codes in force where it will stand, not where it was made. There are no lighter rules for modular, but approval works differently: - **States with a modular program** review the module drawings centrally, approve manufacturers and their quality systems, and oversee inspections in the factory, usually through licensed third-party agencies. Each approved module gets a label or insignia, and the local authority accepts it without opening up the work. - **States without a program** leave the whole building to the local authority having jurisdiction, which may need to arrange factory inspections or rely on third-party reports. - **Site work**, including foundations, utilities, site-built elements and the connections between modules, is permitted and inspected locally in every case. Since 2021 there have also been consensus standards for off-site work, developed by the International Code Council and MBI. **ICC/MBI 1200-2021** covers planning, design, fabrication, transport and assembly; **ICC/MBI 1205-2021** covers inspection and regulatory compliance, including third-party and remote virtual inspection; and **ICC/MBI 1210-2023** covers mechanical, electrical, plumbing, energy and water provisions. A growing number of states and the U.S. General Services Administration have adopted them, so check whether your jurisdiction has. They do not apply to HUD-code manufactured housing. To find the program and contacts for a given state, use MBI's [building codes and contacts directory](https://www.modular.org/?p=58280). Where modular is rare, meet the building department early. ## Design Phase: Working With the Manufacturer ### Choosing a modular manufacturer Build a long list from referrals, industry associations and comparable completed projects, then use a prequalification questionnaire to produce a shortlist. A [supplier prequalification form](https://essential.construction/files/pre-construction/business-development/construction-supplier-prequalification-form/) is a good starting point, and the principles in our article on [prequalifying subcontractors](https://essential.construction/academy/tutorials/why-every-contractor-needs-to-prequalify-their-subs/) apply here too. Evaluate: - Experience with the building type, height and level of design complexity. - Production capacity and available slots against the project size and programme. - Distance from plant to site. Many manufacturers ship within a radius of roughly 350 to 500 miles; beyond that, freight can erode the savings. - Approval in the project's state and any licences needed for its scope (general contractor, electrical, plumbing, structural engineering). - Financial strength, insurance and the depth of its supplier network. - Quality system, inspection records and willingness to host factory visits. ### Define the manufacturer's role Manufacturers can play quite different roles, and the contract must say which one applies. Three arrangements are common: 1. The manufacturer is a subcontractor that builds and delivers modules; the general contractor sets and finishes them. 2. The manufacturer is a subcontractor that builds, delivers and sets the modules, and nothing more. 3. The manufacturer acts as general contractor and is responsible for both factory and site work. In general it is better for the manufacturer to be engaged as a subcontractor building to the project specification than as a vendor selling a product. A sale of goods brings in the Uniform Commercial Code and product-liability rules that suit consumer goods better than buildings. Design responsibility needs equal care. The manufacturer may only advise, or it may take on the structural engineering of the modules. Where it designs a system it should carry the liability for it, and the architect's scope should be adjusted; vague roles breed disputes. Early input from the manufacturer pays for itself: specifications that avoid long-lead products, a key plan optimised for production and lifting, transport cost per module weighed against site installation cost, and early warning, with alternatives, when an idea cannot be shipped or built. ### Split the scope and plan the interfaces Modular projects fail at the interfaces: between factory and site, between modules, and between modules and site-built work. Before design starts, write down who does what, using a responsibility matrix or a detailed [scope of work](https://essential.construction/files/pre-construction/estimating/scope-of-work-template/), so that every cost is priced once and nothing falls between contracts. | Item | Questions to settle | | --- | --- | | Factory scope | What level of finish leaves the factory? Which services are pre-installed and tested? | | Site scope | Who builds foundations, podium, cores, roofs and site utilities? Who closes the mate lines? | | Ownership | Who owns and insures each module in production, in storage, in transit and after setting? | | Tolerances | What tolerances apply to foundations, embeds, modules and stacking? Who surveys and when? | | Connections | Who designs and supplies module-to-module and module-to-foundation connections? | | Sequence | What is the set sequence, and how will delivery, crane time and weather windows be coordinated? | | Inspections | Which inspections happen in the factory, which on site, and who attends? | Share a milestone schedule with every party and review it regularly; a few days' slip in foundations can leave finished modules with nowhere to go. If the architect manages this extra coordination, the fee should reflect it. ![Key questions to ask during the design process for modular construction](https://essential.construction/academy/wp-content/uploads/sites/22/2023/04/image-3.png) ### Use BIM to coordinate design, factory and site A shared model is close to essential. BIM lets the team clash-check services and structure at the mate lines, check stacking tolerances, simulate the set sequence and produce data the plant can use directly. Agree modelling standards, levels of development, file exchange and model ownership up front in a [BIM execution plan](https://essential.construction/academy/tutorials/the-importance-of-bim-execution-plans-in-construction-key-considerations-and-best-practices/); errors that would be fixed on a site-built job can stop a production line. ### Lay out the module key plan Once the design has taken shape, the manufacturer and design team produce a **module key plan** showing how the building divides into modules, how each is numbered and where it sits in the set sequence. Aim for the largest modules that can be shipped and lifted economically, because fewer modules means fewer lifts, fewer deliveries and fewer joints to close. Check that walls, doors, shafts and services do not clash with mate lines, and be prepared to adjust room layouts slightly to suit the module grid. Size limits come from transport rules, which vary by state and province. As a rough guide, the AIA/NIBS introduction for architects gives typical volumetric module sizes of: | Dimension | Typical range | Main constraint | | --- | --- | --- | | Width | 12 to 14 ft | Road permits, escorts and route clearances | | Length | 50 to 60 ft | Trailer length, turning radius, site access | | Height | 11.5 to 13 ft | Bridge and overhead clearances on the route | The manufacturer's engineers normally design the lifting points into each module, and once the key plan fixes bearing points and loads, the foundation can be designed. ### Detail the connections and mate lines Connections need as much attention as the modules. Detail, with the manufacturer and the site contractor: - **Structural ties** between modules horizontally and vertically, and to foundations, podiums, cores and any site-built frame, with access to make them on site. - **Fire resistance** at every joint between modules and between modules and the facade, so that fire-resistance ratings and compartments are continuous. - **Thermal performance**, avoiding thermal bridges through steel connection plates at external mate lines. - **Air and water control**, with continuous barriers across mate lines and a clear sequence for closing them, especially in cold or wet climates. - **Acoustics**, isolating structure-borne sound at connections. - **Placement aids** such as guides and alignment pins, and a decision on whether mate lines are expressed or hidden. Develop any unusual detail with the manufacturer early, and consider a full-size mock-up of a typical module or junction to test buildability and performance before production. ### Design for disassembly If the building may be moved, extended or recovered at the end of its life, design for it from the start: keep connections simple, repeated and accessible, and maximise the share of the building that is made off-site, since a building that is 90 percent modules comes apart far more easily than one that is half site-built. Record how the building was assembled and how it is meant to be taken apart, and hand that record to the owner with the operation and maintenance information. ### Freeze the design Set a firm design freeze before fabrication starts and make sure the owner signs it off. After the freeze, every change has to be priced against lost production, re-engineering and possible rework of modules already built. Run [submittals](https://essential.construction/academy/tutorials/managing-construction-submittals/) and long-lead orders against the production schedule, not the site schedule. ## Construction Phase: Factory, Transport and Set ### Run factory and site work in parallel Once production and site work start, the project manager keeps the two programmes in step. Regular coordination meetings with the manufacturer and site team should track module output, inspection results, foundation progress, survey checks on embeds and anchor bolts, and the delivery forecast. Factory visits are worth the travel: the design team of Carmel Place in New York (see below) reported that weekly visits to the nearby plant caught errors early and built the working relationship the project depended on. Before each module ships, a pre-shipment inspection should check it against the drawings, record open items and confirm openings and finishes are protected. A [project quality plan](https://essential.construction/files/pre-construction/project-planning/construction-project-quality-plan/) covering both factory and site checks avoids gaps between them. ### Plan transport and staging Just-in-time delivery, where modules arrive in set order and are lifted straight off the truck, keeps the site clear and avoids double handling. It depends on permits, traffic, weather and crane availability all lining up, so many projects keep a staging yard near the site holding enough modules to keep the crane busy. On larger mid- and high-rise jobs the plant may need to increase output to match the speed of setting, because the crew can usually set modules faster than one line can build them. Transport rules are set state by state, so a route crossing state lines must satisfy each one. Survey it for clearances, weight limits and turns, and confirm site access for trucks and crane. ### Set, connect and close the envelope Setting day is a planned crane operation. Use an engineered [lift plan](https://essential.construction/academy/tutorials/how-to-plan-your-next-construction-crane-lift/) that covers crane selection and position, ground bearing, rigging, the heaviest and furthest pick, wind limits, exclusion zones and communication. For mobile cranes, a [mobile crane checklist](https://essential.construction/files/construction/safety/inspections/mobile-crane-construction-checklist/) helps with the daily checks; on taller projects a [tower crane](https://essential.construction/academy/tutorials/a-guide-to-construction-tower-cranes/) may be more economical. After each module is landed it is tied to its neighbours and the foundation, then the envelope is closed: infill sheathing at mate lines, continuous air and water barriers, and cladding where the factory did not complete it. This closing work governs airtightness and energy performance, so inspect it closely. ### Site supervisor checklist for setting day - Foundation or podium surveyed and within tolerance, with anchor bolts and embeds checked against the key plan. - Lift plan approved and briefed; crane inspected; rigging certified; wind limits agreed. - Exclusion zones, traffic management and neighbour notices in place. - Delivery sequence confirmed with the plant and haulier; staging area ready if used. - Each module checked on arrival for transit damage and against its label and shipping list. - Fall protection planned for work at module edges and on roofs. - Weather protection ready for open mate lines and roofs. - Connection hardware, fire-stopping and sealants on site before the first lift. - Inspector visits booked for connections and mate-line closure. ## Modular Construction Examples ### Carmel Place, New York City Carmel Place (originally called My Micro NY) in Manhattan's Kips Bay was the winning entry in the city's adAPT NYC competition for micro-apartments. It has 55 studios of roughly 250 to 370 square feet, 40 percent of them affordable, and was assembled from steel-framed volumetric modules, published as 55 apartment modules plus 10 for the building core, made in a factory at the Brooklyn Navy Yard. The modules arrived with services installed, and the design team stressed how much the plant's proximity helped. The city waived some zoning rules, including the minimum unit size, to allow the pilot. ### 220 Terminal Avenue, Vancouver Vancouver's first temporary modular housing project, completed in early 2017 on vacant city land, provides 40 self-contained units with their own kitchens and bathrooms plus shared laundry and amenity space. Its above-grade foundation barely disturbs the ground, so a site that would otherwise need remediation could be used, and the building is designed to be moved. The housing agency reported that complex approvals took away part of the time saved, a reminder that permitting needs as much planning as the factory work. ### Pocket Living, London In 2017 the Mayor of London invested £25 million in developer Pocket Living to start at least 1,059 affordable homes by March 2021, about a third of them factory-built. For more cases from the affordable-housing sector, see the white paper on [modular construction for multifamily affordable housing](https://essential.construction/files/information/white-papers/modular-construction-for-multifamily-affordable-housing/). ## The Modular Construction Market Today MBI's 2026 U.S. Permanent Modular Construction Industry Report estimates the U.S. permanent modular market at $20.5 billion in 2025, about 5.1 percent of construction activity in the segments it tracks; its Canadian report puts modular at around 5.5 percent of that market. Several large general contractors have opened modular divisions or partnered with manufacturers. Collaborative delivery, shared models, factory automation and the ICC/MBI standards are making off-site construction a normal option to test on every project. For a view of where the industry is heading, see the white paper [Modular Construction: From Projects to Products](https://essential.construction/files/information/white-papers/modular-construction-from-projects-to-products/). ## Frequently Asked Questions About Modular Construction ### What is modular construction? Modular construction is a building method in which sections of a building, either complete three-dimensional modules or panels and sub-assemblies, are made in a factory, shipped to site and assembled on foundations built at the same time. Overlapping factory and site work is what shortens the schedule. ### What are the main types of modular construction? The two basic types are volumetric modular, where complete 3D boxes of space are built off-site, and non-volumetric or panelized construction, where walls, floors, roof trusses and facade units are prefabricated. Pods, permanent and relocatable buildings, and hybrids of modules, panels and site-built work are common variations. ### What are the steps in the modular construction process? Commit early, choose a collaborative delivery model, prequalify a manufacturer, design the module key plan and connections together, obtain approvals, freeze the design, build modules and site works in parallel, transport and stage, set and connect, then finish and hand over. ### Is modular construction faster than traditional construction? Usually, yes. Because modules are built while the site is prepared, the Modular Building Institute cites schedules 30 to 50 percent shorter than site-built construction on well-coordinated projects. Late changes, one-off designs and slow approvals erode that saving. ### Is modular construction cheaper? Not automatically. Costs are usually more predictable and a shorter programme reduces financing and site overheads, but transport, cranes, stronger module structures and up-front engineering add cost. Compare total hard and soft costs, including earlier occupancy. ### Do modular buildings have to meet the same building codes? Yes. In the United States, permanent modular buildings must meet the same state and local codes as site-built buildings, usually based on the IBC or IRC, although plan review and factory inspection often go through a state modular program or third-party agency. ### What is the difference between modular and manufactured homes? Manufactured homes are built on a permanent steel chassis to the federal HUD Code. Modular homes are built to the same state and local codes as site-built homes and are set on permanent foundations, so they are generally financed, valued and permitted like site-built houses. ## Related Templates and Guides - [Everything You Need To Know About Modular Construction](https://essential.construction/academy/tutorials/modular-construction/): a shorter introduction for owners and contractors - [The Importance of BIM Execution Plans in Construction](https://essential.construction/academy/tutorials/the-importance-of-bim-execution-plans-in-construction-key-considerations-and-best-practices/) - [Common Types of Construction Contracts and Their Use](https://essential.construction/academy/tutorials/common-types-of-construction-contracts-and-their-use/) - [How To Plan Your Next Construction Crane Lift](https://essential.construction/academy/tutorials/how-to-plan-your-next-construction-crane-lift/) - [Fundamentals of Construction Scheduling](https://essential.construction/academy/tutorials/fundamentals-of-construction-scheduling/) and [Lean Construction: Pull Planning Explained](https://essential.construction/academy/tutorials/lean-construction-pull-planning-explained/) - [Controlling Quality on the Construction Site](https://essential.construction/academy/tutorials/controlling-quality-on-the-jobsite/) - [Saving Time With Modular Bathroom Pods](https://essential.construction/files/information/white-papers/saving-time-with-modular-bathroom-pods/) (white paper) Further reading: the Modular Building Institute at [modular.org](https://www.modular.org/) and the AIA and NIBS guide *Design for Modular Construction: An Introduction for Architects*.