Who this guide is for
- Self-builders choosing a structure before a design is fixed
- Owners given two options by a designer and unsure what separates them
- Anyone comparing quotations that assume different build methods
- Owners who want to know what a method will demand of them later
- Buyers trying to understand how an existing house was built
What the comparison is actually about
Read together, the five entries are not arguing about strength. They differ in where the work happens, when the information has to be finished, what the wall will let you attach to, where the services can go, and who absorbs the difference between the drawing and the building.
Those five axes recur in every one of the entries, in their own vocabulary. Setting them out as a common frame is the only way to compare systems that are each forbidden to compare themselves.
- When the design stops being changeable
- Where the services are allowed to run
- What a fixing can reach, and whether its position was decided in advance
- How much deviation the method can absorb, and where
- What the structure needs while the building is still open to weather
When the design stops being changeable
Masonry and a site-built timber frame keep their options latest, though neither keeps them indefinitely: layout changes in a framed building are structural changes even when no member is being removed, because a plan that works well for rooms may leave too little uninterrupted wall to brace a storey.
A cold-formed steel frame is usually panelised away from site, so openings, connection points and service holes are set during fabrication and the sequence is set before delivery. A structural insulated panel building is made to a layout, so a late change to an opening or a fixing position is an alteration to a manufactured structural element. An insulating concrete formwork wall is stacked dry and filled, so the point of no return is the fill.
What the wall will let you fix to
This is the axis owners notice years later. In masonry the strength is the section, so anything that removes material from it, a chase, a recess, a flue, removes part of the load path, and which of those are acceptable is settled before the wall is built rather than negotiated once the trades are on site.
In a framed wall, fixings land back on framing members whose positions were set for structural reasons, and where they need to go is worth establishing before linings close the frame in. In a light steel frame, heavy fixings cannot rely on a thin section, so backing or noggings are added during fabrication and their positions have to be known before the panels are made.
In insulating concrete formwork the ties are the map. They hold the faces apart during the fill, and afterwards those same positions become where a handrail, a kitchen run or a cladding rail can be attached, because the faces have no holding power. A fixing decided late has nowhere to go except into the core.
Where the services are allowed to run
In a timber platform frame the stud cavity is competed for by insulation, cables and pipes, and what passes through it is drilled or notched through members that are carrying, so the route is agreed with the designer rather than found by the trade that arrives first.
In a steel frame the service holes are formed at fabrication in positions the designer has accepted, sized and placed so the web retains the shape it depends on; a hole cut later removes part of the very thing that lets a thin section behave as a member. In insulating concrete formwork the runs are formed in the inboard insulating face rather than in the core, and whether a run crosses a tie is settled with the designer.
Structural insulated panels have nowhere neutral at all. A chase into a panel removes facing, core and sealing at the same place, which is why an inboard batten zone is part of the system rather than an extra layer.
Tolerance and what inherits it
Every method hands a line to whatever is built next, and they differ in how forgiving that handover is. An insulating concrete formwork wall inherits the substructure: the first course sets the plumb and line the rest of the wall follows, and deviation in the substructure becomes deviation in the wall.
A framed panel arrives at a fixed size. A light dry frame lands on a heavy construction that was recently wet, and both the anchorage and the separation between them are formed at the same line; setting out there is unforgiving, because a panel positioned late cannot be adjusted once the anchors are in.
Movement, weather and the gap before enclosure
Masonry changes length with temperature and moisture, and where the wall is expected to change length is a design decision expressed as movement joints rather than as cracks the wall chooses for itself.
A timber frame shortens slightly as it dries, and the shrinkage concentrates in the horizontal timber at each floor band, so anything rigid and continuous past that band has to be detailed for it. A steel frame does not shrink but conducts, which moves the insulation strategy out of the stud zone and makes the frame designer and the wall designer unable to work in sequence.
All of the light methods share one exposure. A frame is at its most vulnerable between erection and weathertightness, and protection during that period is a planning question whose record belongs with the handover information.
What none of these pages will tell you
No entry in the library states which of the five is better, and this guide does not either. The comparison exists so that a proposal can be understood on the terms it is actually made on, and so that the questions above are asked while there is still time for the answers to change something.
Comparing house structures on even terms
- 1Ask, for each option, at what point the design stops being changeable.
- 2Ask which walls are carrying and which are bracing in the proposed layout.
- 3Ask where the services are intended to run and who agrees that route.
- 4Ask what a fixing into each wall type will actually reach.
- 5Identify now where heavy items will later be hung, and ask how that is provided for.
- 6Ask how much deviation the method can absorb, and where it is absorbed.
- 7Ask what the substructure has to hand over, and how accurately.
- 8Ask what protects the structure between erection and weathertightness.
- 9Ask where the insulation sits relative to the structure in each option.
- 10Ask what record of the structure will be handed over at completion.
- 11Compare quotations on the same scope rather than on the same drawing.
- 12Ask what each option would make difficult if the house were altered later.
Common mistakes to avoid
- Comparing the options as materials when the differences that matter are about programme, services, fixings and tolerance.
- Assuming a factory-made structure needs less design, when the design has to be finished earlier.
- Deferring the fixing positions for kitchens, sanitaryware and guarding until the linings are going on.
- Treating light steel framing as timber framing in another material, when the conductivity changes the whole wall build-up.
- Reading the insulating units of a formwork wall as the wall, when the wall is the cast core.
- Cutting a chase into a structural insulated panel, which removes structure and insulation in the same stroke.
- Changing a room layout late in a framed building without asking what it does to the braced wall lengths.
- Leaving a frame exposed to weather without having agreed who is responsible for protecting it.
When to involve a professional
- Nothing here establishes which structure suits a particular project; that is a determination for the designers advising on the site, the brief and the budget.
- No member size, section, fixing schedule, spacing or capacity appears in this guide, and none should be inferred.
- Fire and acoustic behaviour are properties of complete tested assemblies and of the construction around them, and neither is stated here.
- Whether a section, panel or wall may be cut, drilled or altered is a determination for the structural designer and, where relevant, the supplier of the system.
- Where the insulation sits and what any arrangement achieves in a given climate is assessed by a qualified professional for the whole build-up.
Frequently asked questions
Questions readers ask about this topic
Which of these is the best structure for a house?
No entry in the library ranks them and this guide does not either. They answer the same need differently, and what suits a project depends on the site, the design, the programme and the people building it, which is a determination for the advising professionals.
Why does the choice affect where I can hang a shelf?
Because each system gives a fixing something different to reach. Masonry offers its own section, a framed wall offers members whose positions were set structurally, and an insulating formwork wall offers tie positions, because the insulating faces have little holding power.
Does a factory-made structure mean less work for me?
It moves the work earlier. Openings, service holes, connection points and backing are set during fabrication, so decisions that would be made on site in a masonry house have to be made before anything is manufactured.
Why is the insulation position different for a steel frame?
Because every stud and every track is a metal path running from the lining to the sheathing, and the frame fixes where those paths are before it reaches site. What the surrounding build-up does about them belongs to the wall designer rather than the frame designer.
What happens if I change the layout late?
In a framed building, layout changes are structural changes even when no member is removed, because the braced wall lengths may no longer be available. In a manufactured system, a late change alters something that has already been made.
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