A spectrum, not a product
Modular is binary. Either the box arrives finished or it does not. Panelisation is a dial, and the position of the dial is the whole negotiation.
At the open end, a panel is a framed wall: studs, plates, sheathing, nothing else. It arrives flat, it is stood up in hours rather than days, and every trade that follows works exactly as they would on a stick-framed house. At the closed end, a panel arrives with insulation, a weather barrier, services roughed into the cavity, sometimes windows already fitted and sealed. The building is weathertight faster and a large part of the trade sequence has moved indoors.
The dial has a cost. A closed panel is a commitment made early. Every socket position, every pipe run and every window opening is fixed when the panel is manufactured, which is typically weeks before anything reaches the site. Changing one afterwards means cutting into a finished, insulated assembly, and the saving that justified the panel disappears with it.
Structural insulated panels are a different animal
A structural insulated panel is not a framed wall with insulation added. It is a sandwich: rigid foam bonded between two structural skins, most often oriented strand board, acting compositely so the panel itself carries load. There are no studs to bridge heat across, which is the main reason people specify them.
The trade-off is that a SIP building is airtight in a way a framed building is not, and airtightness is a consequence rather than a feature. A house that does not leak has to be ventilated deliberately, which becomes a mechanical design problem rather than an accident of construction. That is not a drawback of panels. It is a requirement that arrives with them, and a project that treats it as optional produces a tight house with poor air.
Openings, service routes and any later alteration are also engineered rather than improvised. Cutting a new opening in a SIP wall is a structural change, not a carpentry job.
Precut kits, and what the word kit hides
The Census Bureau defines a precut package as lumber or timber, cut to exact size, length and quantity, shipped from a factory to be assembled on site. [1] No panels, no assemblies, just an exact bill of materials with the cutting already done.
That is the honest description of most timber frame and log packages, and of many so-called kit homes. The saving is in waste, in cutting labour and in not having a pile of the wrong lengths on site. It is not a saving in construction. Somebody still builds the entire house, and the kit supplier is usually not that somebody.
The word kit does a lot of quiet work in the marketing of these packages. A kit implies completeness. Read the inclusion list instead: it is the only document that tells you what you are buying, and the gap between the kit and a finished house is where the budget goes.
Panels are flat and foundations are not
A panel is manufactured to a tolerance measured in millimetres, on a jig, on a level factory floor. A foundation is built outdoors by a different contractor, in weather, to a tolerance an order of magnitude looser. Panelised construction puts those two tolerances in direct contact, and the panel always loses.
The failure is not dramatic. A foundation that is out of level or out of square by a small amount does not stop the panels going up. It means the first course sits on a packing shim, the shim grows along the wall, and by the far corner somebody is scribing a component that was supposed to drop into place. The saving in erection time goes into that scribing, and everybody blames the panels.
Experienced panel suppliers deal with this by specifying the foundation tolerance in the contract and requiring a survey before delivery. If your supplier does not raise the subject, raise it yourself, and get the required tolerance in writing before the concrete is poured. It is the cheapest piece of coordination on the job and it protects the thing you paid extra for.
The category is bigger than the one everyone talks about
The Census Bureau reports panelised and precut units together as a residual alongside modular and site-built. In 2025 that residual accounted for 16,000 of the 1,005,000 single-family completions, against 14,000 modular. [2]
The gap is small in absolute terms and it has been consistent: the panelised and precut residual has been at or above modular in most recent years. The publicity has gone the other way round for a decade, because a crane setting a finished box makes a better photograph than a truck of flat panels.
For a buyer, the useful implication is that the market is not asking you to choose between a factory house and a site-built house. It is offering a dial, and most of the people who have actually moved work indoors chose a position in the middle of it. You can read the counts yourself on the front sheet and in the Bureau's table.
Questions
- Do panelised houses need a crane?
- Usually, but a much smaller one than a modular set, and often for hours rather than a day. Panels are heavy and awkward rather than enormous. Site access still governs, and it is worth confirming before the panels are ordered rather than after.
- Can I change the plan after ordering panels?
- Assume not. The point at which the manufacturer releases the panel drawings is the point at which the design is fixed. Ask for that date in writing and treat it as the design freeze, because that is what it is.
Sources
- 1U.S. Census Bureau. Survey of Construction: Definitions. Accessed 2026-08-29
- 2U.S. Census Bureau. Type of Construction Method of New Single-Family Houses Completed, Characteristics of New Housing, 2025 data, released 1 July 2026. Accessed 2026-08-29