Building envelope · Facades & Cladding
Sheeted Metal Wall Cladding System
A reference for how a site-assembled metal wall divides weathering, thermal and air control duties between separately fixed layers, and why a break in the liner reports as a leak that is not coming from outside.
Educational reference entry. How this system behaves depends on climate, jurisdiction, loading, substrate, the adjacent systems it meets, how the building is used, the manufacturer's instructions and qualified professional design.
Overview
What sheeted metal wall is
A sheeted metal wall is built in operations rather than delivered as a wall. Side rails span between the frames of the structure, a profiled liner sheet is fixed across them and its laps are sealed, a spacer system stands off that liner, insulation is laid over it, and a profiled outer sheet is fixed through to the spacers. Each layer arrives and is fixed separately, and each is the substrate for the next.
The outer sheet here is the weather line, not a screen in front of one. It is expected to shed water, and the assembly behind it is not organised as a drained cavity with a separate control layer. That is the fact which separates this wall from a rainscreen, and it is why the sealing of the outer laps and the closure of the sheet at every edge matter in a way they would not on a screen.
The liner sheet does the work the outer sheet is not doing. It is the internal face, and it is also the air and vapour control element of the wall, which makes its side laps, end laps and perimeter sealing the airtightness of the building. Because it is fixed early and covered immediately, it is also the layer that is hardest to revisit.
The spacer system between liner and outer sheet is what makes the build-up dimensional. It transfers wind load from the outer sheet back to the rails, sets the depth available for insulation and holds the insulation at that depth, and it does all three at once — which is why it is a component rather than an accessory.
Terminology
Common names and aliases
These names describe the same assembly. The encyclopedia keeps one entry per system so that a trade term or a regional name never becomes a second, thinner page.
- built-up twin skin metal wall
- profiled metal wall cladding
- site-assembled metal wall
- industrial wall sheeting
- liner and outer sheet wall
Purpose
What this system is intended to do
The job the assembly exists to perform, conceptually. An intention is not a guarantee that any particular build achieves it.
- Enclose a framed building with a wall built from separate layers fixed in sequence on site.
- Shed weather at the outer profiled sheet, which is relied on as the weather line rather than as a screen.
- Carry air and vapour control at the liner sheet, whose laps and perimeter are that control.
- Hold a thermal layer between the two sheets at a depth set and maintained by the spacer system.
- Transfer wind pressure and suction on the outer sheet back through the spacers and the side rails into the structure.
- Close the profiled sheets wherever they stop, at sills, eaves, corners and openings, where a profile leaves an opening of its own.
Composition
The roles this system is made of
What each part does in the assembly and what it depends on — never a product, a thickness, a fixing or a determination that anything is adequate for the role.
Order is meaningful in this system. The roles below sit in sequence, and moving one relative to another changes what the assembly does. The sequence is conceptual only: it states no thickness, no dimension, no fixing and no order of work on site.
- Layer 1 of 8. Order is meaningful.Primary supportSide rails and the structural frame
The horizontal members spanning between the frames of the building, which receive the liner sheet and, through the spacers, the outer sheet. Their positions set where anything can be fixed, so they are the first decision in the wall and the one everything else is dimensioned from.
- Layer 2 of 8. Order is meaningful.Control layerProfiled liner sheet with sealed laps
The inner profiled sheet, which is the internal face and the air and vapour control element at the same time. Its continuity is a property of its side laps, its end laps and its sealing at every perimeter, and it is covered by the rest of the build-up as soon as it is fixed.
- Layer 3 of 8. Order is meaningful.AttachmentSpacer, bracket and rail system
The components standing between liner and outer sheet. They transfer wind load from the outer sheet back to the rails, set the depth of the cavity the insulation occupies and hold the insulation at that depth, and their pattern is what the outer sheet's fixings land on.
- Layer 4 of 8. Order is meaningful.Thermal layerInsulation over the liner
The layer laid over the liner and dressed around the spacers, filling the depth the spacer system creates. Because it is placed rather than fixed and then immediately covered, whether it is continuous and at its intended depth is decided during one short part of the sequence.
- Layer 5 of 8. Order is meaningful.Finish surfaceProfiled outer weathering sheet
The outermost layer, which here is the weather line rather than a screen in front of one. Its profile governs the fixing pattern, the filler pieces needed at every edge, the load it passes back to the spacers and how it behaves where it is cut, lapped or turned.
- Layer 6 of 8. Order is meaningful.Jointing and sealingSealing at both sheets
The lap sealing at the liner and at the outer sheet, which is the same operation doing two different jobs. At the outer sheet it is about water arriving from outside; at the liner it is about air and moisture leaving from inside, and the consequence of missing it shows up at the other sheet.
- Layer 7 of 8. Order is meaningful.Edge and terminationFlashings, fillers and closures
The sill, eaves, corner, verge and opening pieces, and the profile fillers that close the shaped voids a profiled sheet leaves wherever it stops or changes direction. Every one of them is a place where the sheeting plane has to become something else.
- Layer 8 of 8. Order is meaningful.ProtectionCoating, cut edges and fixings
The coated surfaces of the sheets and the condition of every cut edge, drilled hole and fastener head. The wall is built by cutting and piercing coated metal on site, so what happens at those points is a property of the installed assembly rather than of the delivered sheet.
Interaction
How the parts work together
The reason this is a system rather than a list of parts: what depends on what, and what stops working when one part is changed.
The rails, the spacers and the outer sheet are one dimensional problem. Set out the side rails without knowing the spacer system and the outer sheet has nowhere to land; change the outer profile and the fixing pattern, the filler pieces and the load reaching the rails all change with it.
The insulation is only as thick as the spacer system lets it be. Compress it at every spacer and the layer that was drawn as continuous is not, and the places where it is thinnest are also the places where a conductive component crosses it, so the two effects coincide rather than average out.
Sealing the outer laps and neglecting the liner laps produces a defect that presents as a leak and is not one. Warm moist air from inside passes the unsealed liner, reaches the cold outer sheet and condenses on it, and what runs down the inside of the outer sheet and appears at a lap is being read as rain that has come in.
The two sheets are doing opposite jobs and are commonly fixed by the same operation on the same day. Because the liner is covered as soon as it is complete, everything depending on it — airtightness, the position of the vapour control line, the insulation's protection from internal air — is settled before anyone can see the wall as a whole.
Materials
Material families commonly met in each role
Commonly encountered, not recommended. Whether a material suits a given project depends on the whole assembly, the exposure, the manufacturer's documentation and qualified professional review.
Primary support
Side rails and the frames they span between are commonly formed in these families. What any given rail arrangement can carry is an engineering matter established for the particular building.
Control layer
Liner sheets are commonly met in profiled metal families, sometimes with a separate sheet material where the liner alone is not being relied on for vapour control. Which arrangement is used in a given wall is a design decision rather than a property of the sheet.
Thermal layer
These families are commonly encountered between the sheets. How readily each is compressed where a spacer crosses it, and how it behaves when laid over a profiled liner, differ between them.
Finish surface
Outer sheets and panel faces are commonly met in these families. They differ in how they are formed, how they are coated and how they behave at cut edges, and those differences bear on the terminations more than on the field of the wall.
Jointing and sealing
Lap sealing at both sheets is commonly carried out with materials from these families. What is used at the liner and what is used at the outer sheet are commonly different products doing different jobs, and are read from the manufacturer's documentation.
Edge and termination
Flashings, closures and trims at sills, eaves, corners and openings are commonly formed in these metals. Which metal may sit against which sheet and which fastener without one attacking the other belongs with the product documentation and the designer.
Boundary
Where this system ends and meets another
The edge of this system. Everything above is inside it; each junction below is a condition at its boundary, where an adjacent system or an adjacent building condition takes over. Junctions are where most assemblies actually fail, so they are set out explicitly rather than left inside the prose. What resolves one is a detail designed for the specific building — not a rule of thumb.
Side rails on the frame
The frame's side rails are structural participants in the building as well as the plane the wall is fixed to, so the sheeting layout and the rail layout are the same drawing. A change to either is a change to both, and the bracing planes in the frame have to coexist with the wall's fixing pattern.
Read about Portal Frame →Sheeting carried on a framed structure
Where the wall is hung on a steel frame that is not a portal, the columns and the secondary steel define where the rails can go and how far the sheets span. The frame's own movement under load then has to be accommodated where the sheeting is fixed to it.
Read about Steel Frame →The same build-up turned horizontal at the eaves
The roof equivalent of this wall meets it at the eaves, and the two build-ups have to be made continuous there: liner to liner, insulation to insulation and outer sheet to outer sheet, at a junction where the water on the roof is being collected and the water on the wall is running past.
Read about Twin-Skin Metal Roof →A panel roof over a sheeted wall
Where a factory-made panel roof sits over a site-assembled wall, the layers do not correspond one to one at the junction, because what arrives bonded into a single component on one side arrives as three separate operations on the other. The eaves detail has to reconcile that.
Read about Composite Panel Roof →The liner as part of a whole-enclosure line
The liner is the wall's contribution to a barrier that has to continue onto the roof, down to the floor and around every opening. Every one of those changeovers is from a profiled sheet onto something with a different shape, which is the recurring difficulty of making a profiled liner airtight.
Read about Air Barrier System →Openings trimmed through the sheeting
An opening interrupts the liner, the insulation, the spacers and the outer sheet in one line, and each has to be trimmed and closed. The profile of the outer sheet means the closure at the head, jambs and sill is a shaped piece rather than a flat one.
Read about Window Opening Interface →The base of the sheeting at the slab edge
The bottom of the wall is where the sheeting stops, where water running down the outer sheet has to be discharged clear, and where the liner's air line has to be closed onto the floor construction. It is also the line most exposed to impact, splash and standing water from outside.
Considerations
Topics worth discussing
Which topics genuinely apply to this system and what to raise about them. Measured values, classes and ratings come from a qualified professional's design for the specific building, not from a reference page.
- Moisture
- Because the liner carries the vapour control duty and the outer sheet is cold, a break in the liner puts internal air against a cold metal surface. Whether that is a risk in a given building depends on the internal conditions, the climate and the whole build-up, and is assessed by a qualified professional.
- Thermal
- The insulation is crossed by the spacer system and compressed wherever it is held, so the thermal layer's continuity is a function of the spacers rather than of the boards or rolls. What a given arrangement means for a particular building is assessed rather than assumed.
- Buildability
- The wall is built from the inside out in separate operations, and each layer covers the last. The liner in particular is complete and hidden before the wall exists as a wall, so sequence and supervision decide what can never be inspected again.
- Durability
- The assembly is made by cutting, drilling and fixing coated metal on site, and every cut edge, hole and fastener is a point where the coated system has been interrupted. Contact between dissimilar metals at those points is a question for the designer and the product documentation.
- Interfaces
- A profiled sheet leaves a shaped opening wherever it stops, so every termination needs a closure made for that profile. The number of such closures, rather than the area of sheeting, is what makes one of these walls complicated.
- Documentation
- The spacer arrangement, the sealing at the liner and the closures at each termination are not visible in a finished wall. Recording them is what makes later alteration, and later diagnosis of what appears to be a leak, possible.
Design
Questions the design has to answer
The decisions this assembly turns on. They are questions rather than answers, because the answer depends on the building.
- Where are the side rails, and has the spacer system been chosen before they are set out?
- What is the vapour control element in this wall, and is it the liner sheet itself?
- How is the liner sealed at side laps, end laps and every perimeter, and who is doing that sealing?
- What depth is available for insulation, and what holds it at that depth between the spacers?
- What happens to the insulation where a spacer crosses it?
- Which closures does the chosen outer profile need at sills, eaves, corners and openings?
- How does the base of the wall discharge water clear of the building, and how is the air line closed there?
- Where this wall meets the roof, which build-up is on the other side of the junction and how do the layers correspond?
Boundaries
Commonly misunderstood points
Distinctions that are easy to blur, and the places where a familiar term means something narrower than it sounds.
- This is not a rainscreen. A rainscreen's premise is that the outer screen is not relied on to exclude water, with a drained ventilated cavity and a separate control layer behind it. Here the outer sheet is the weather line and the liner is the control layer, which reverses where the duties sit.
- It is not a precast panel facade either. There the joints between large units do the weathering and the units are hung or restrained back to the structure; here the sheets lap over one another, are fixed through to rails, and are continuous rather than jointed at intervals.
- It is the wall case of a build-up the roof registry already covers, not a restatement of it. The differences are real: water runs down rather than across, the sheets are oriented differently, the spacers hold a vertical rather than a horizontal load path, and the terminations are sills, corners and openings rather than eaves, ridges and verges.
- A composite panel wall, where outer sheet, core and liner arrive bonded into one component, is a different assembly from this one in the same way that a composite panel roof is different from a built-up roof.
- Water appearing at an outer lap is not necessarily rain. On this build-up it is commonly internal air that passed an unsealed liner and condensed on the cold sheet, which is a defect in a layer nobody can see.
Conversations
Questions for qualified professionals
Bring these to the relevant qualified professional, manufacturer or authority. Requirements vary by project and location.
- What is carrying the vapour control duty in this wall, and what has been assessed about the internal conditions?
- How is the liner sealed, and what inspection is happening before it is covered?
- How has the wind load path from the outer sheet through the spacers to the rails been established?
- What is the insulation depth between the spacers, and what happens to the layer where each spacer crosses it?
- Which closures and fillers does the selected profile require, and are they all detailed?
- What has been considered about dissimilar metals at fixings, cut edges and flashings?
- How does this wall meet the roof, and who is detailing the eaves junction between the two build-ups?
What this page does not do
- This entry describes how the assembly is organised. It is not a specification, a wall build-up for a particular building, or a substitute for design by a qualified professional.
- No thermal, fire or weathertightness performance is stated here; those are properties of complete, tested and correctly installed assemblies in a specific context.
- Wind load, fixing arrangements and the structural behaviour of rails and sheets are engineering determinations and are never inferred from a general reference.
- Regulated questions about the external surfaces of a building vary by jurisdiction, by building height and by use, and must be verified against local requirements.
Related systems
How this system relates to others
Every link states what the relationship actually is, rather than leaving a bare list of related pages to be read as a suggestion.
Alternatives
Different systems answering the same need. Listing them together is not a comparison and does not suggest one is better — which, if either, suits a project is a design decision.
Commonly built alongside
Systems routinely present in the same building without a junction recorded between them and this one. Where two systems do meet, the junction is set out above instead.
Applications
Building contexts this system is used in
The functional parts of a building this assembly is commonly met in. This is membership, not a ranking and not a recommendation: several systems answer any one context, and which of them suits a project is a design decision. A context appearing here does not mean the system is suitable, permitted or adequate for it.
- Facade · Envelope
Go deeper
Related Build Design Hub guides
Planning guidance behind the decisions this assembly involves.
Preparation
Related planning checklists
Owner-side preparation before the conversation where this system comes up.
Facade and Cladding Systems
Outer skins carried on a wall that is already complete behind them, where the support, the joint and the cavity carry the durable knowledge rather than the finish.
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