Direct answer: To specify terracotta facade panels, establish the elevation grid and visual intent first, then coordinate panel geometry, finishes, joints, support system, movement, interfaces and replaceability. Convert project wind, fire, impact, moisture and durability criteria into verifiable submittals, including representative samples, calculations, test reports, installation drawings and a project mock-up before approval.
A successful specification defines an integrated cladding system: panels, joints, clips, rails, brackets, anchors, cavity, protected wall layers, flashings, fire-safety measures and interfaces.
The architect can lead the visual, dimensional and coordination requirements. However, project-specific structural, wind, seismic, fire and life-safety decisions must be completed or reviewed by appropriately qualified professionals under the applicable local laws, codes and approval procedures.
1. Start with the elevation module—not an isolated panel
The most useful early question is not simply “Which panel size?” but “How should the complete facade grid resolve?”
Set out primary horizontal and vertical control lines across:
- Floor edges and parapets
- Window heads, jambs and sills
- Building corners and returns
- Entrances, soffits and recessed zones
- Movement joints
- Louvres, signage and service penetrations
- Changes in material or facade depth
Test whether the module can continue through these conditions without narrow cuts, disruptive joint offsets or excessive specials.
Nominal module versus actual panel size
Keep these dimensions separate:
- Nominal module: the repeating elevation dimension.
- Actual panel dimension: the manufactured panel size.
- Joint dimension: the intended visible separation between panels.
- Coordination zone: space for tolerances, supports, movement and access.
State which dimensions are design intent and which remain subject to engineering and manufacturing limits. A rendered module is not automatically manufacturable or structurally suitable.
Coordinate panel orientation and geometry
Record panel orientation and identify flat, profiled, corner, reveal, soffit, perforated and cut units separately. Notches and unusual edges require product-specific engineering review rather than being treated as routine site cuts.
2. Define joints, tolerance and movement together
Joint width cannot be selected only as a graphic preference. The joint has to accommodate manufacturing variation, supporting-wall tolerance, rail alignment, installation clearance and movement within the assembly.
Ask the facade team to identify:
- Panel manufacturing tolerances
- Substrate and structural-frame tolerances
- Adjustment available at brackets, rails and clips
- Fixed and sliding points within the support system
- Thermal and moisture-related movement provisions
- Building movement and structural deflection criteria
- Joint alignment at interfaces
The EOTA assessment document for mechanically fixed external-wall cladding kits specifically treats the assembled kit—including cladding elements, fixings, profiles and brackets—and requires manufacturing and installation tolerances and temperature- or humidity-related deformation to be considered in wind assessment.
Do not use sealant in open panel joints unless the selected, engineered system specifically requires it. In a drained and ventilated rainscreen, the visible cladding is not normally expected to be the sole watertight layer.
3. Specify the visual range, not just one colour chip
Colour, tone and surface character should be controlled through an agreed range rather than an expectation that every fired-clay unit will look identical.
Define the following where relevant:
| Appearance item | What the specification should establish |
|---|---|
| Body colour | Intended colour family and acceptable tonal range |
| Surface finish | Natural, engobed, glazed or other verified finish |
| Texture | Smooth, sanded, combed, grooved or project-specific profile |
| Gloss | Intended visual character under representative lighting |
| Orientation | Whether texture or profile has a directional installation |
| Distribution | How approved tonal variation should be blended across elevations |
| Reference | Signed samples and an approved facade mock-up |
Review multiple production-representative samples in relevant lighting. Use a larger mock-up to assess colour, joints, fixing visibility, corners and normal variation; it does not replace structural, fire or durability evidence.
4. Describe the complete fixing and support concept
A panel needs a traceable load path through clip, rail, bracket and anchor to the supporting construction. Do not name a panel while leaving its support system undefined.
Require the design team or specialist contractor to document:
- Panel-to-clip engagement
- Clip material and retention method
- Vertical and horizontal rail arrangement
- Bracket spacing and adjustment
- Fixed and sliding connections
- Dead-load support and wind-load transfer
- Edge, corner and high-suction wind zones
- Anchor type and actual substrate
- Corrosion resistance and material compatibility
- Provisions for panel removal and replacement
Official UK guidance warns that cladding calculations should address wind-pressure zones, fixing patterns, pull-through, pull-out, safety factors, substrate testing and installation methodology. It also notes that inadequate assessment can create a falling-component hazard. See the UK government’s wind-loading guidance for cladding systems.
For projects using US practice, ASCE identifies ASCE/SEI 7-22 as its current minimum-design-load standard. European projects may refer to the applicable Eurocode and National Annex; the European Commission’s Joint Research Centre lists EN 1991-1-4 as the Eurocode part addressing wind actions.
These references are not interchangeable default specifications. The project structural or facade engineer must determine the governing code, design actions, combinations, safety factors, serviceability limits and required testing for the actual site and building.
5. Request technical evidence that matches the proposed assembly
A report for “terracotta” in general is not enough. Evidence should identify the tested or assessed panel geometry, thickness, fixing arrangement, spans, joint configuration, substrate and support components.
The following matrix can be adapted for tender and technical submittals:
| Topic | Evidence to request |
|---|---|
| Product identity | Manufacturer, reference, intended use and manufacturing location |
| Geometry | Drawings, profiles, dimensions, mass, tolerances and permitted orientation |
| Appearance | Production samples, finish range and agreed mock-up |
| Panel mechanics | Relevant bending, groove, edge or connection evidence |
| System wind resistance | Calculations and/or tests representing the proposed panel, fixing and support configuration |
| Anchors and substrate | Product data and project-specific verification where required |
| Water management | Joint, cavity, flashing and drainage details |
| Impact | Evidence appropriate to exposure, access and occupancy |
| Fire | Product and complete-assembly evidence required by the applicable fire strategy and jurisdiction |
| Durability | Relevant water absorption, freeze-thaw, thermal cycling, finish, corrosion and compatibility evidence |
| Delivery and use | Production-control documents, installation instructions, inspection plan and replacement procedure |
Within the European system, the Construction Products Regulation provides a common language for declaring product performance. The European Commission explains that a Declaration of Performance communicates assessed performance, while assessment and verification procedures address its constancy. A declaration or CE mark does not by itself decide whether a product is suitable for a specific building; national rules and the project design remain decisive. See the Commission’s current Construction Products Regulation overview.
EOTA’s document includes routes for assessing wind, impact, component mechanics, water-related characteristics, dimensional behaviour and durability. Use product-specific evidence—not the EAD alone—to confirm what was assessed.
6. Treat fire performance as an assembly question
Do not reduce facade fire safety to the reaction-to-fire classification of the visible terracotta panel. The fire strategy may also need to consider insulation, membranes, brackets, rails, gaskets, cavity geometry, cavity barriers, fire-stopping, openings and attachments.
Requirements vary with jurisdiction, building height, use, boundary conditions and regulatory route. England’s current Approved Document B publication page illustrates how external-wall and cavity provisions can change over time.
All fire classifications, test routes, cavity-barrier locations and system acceptance must be determined by the project’s qualified fire professional and approving authority under the current local regulations. Never describe a complete facade as compliant solely because one component has a favourable classification.
7. Use a staged approval workflow
A practical workflow is:
- Concept stage: establish module, joint rhythm, orientation, texture and key interfaces.
- Design development: coordinate panel families, openings, cavity and supports.
- Tender: issue performance requirements and an evidence schedule.
- Specialist design: review calculations, tests, anchors, movement and shop drawings.
- Samples and mock-up: approve appearance and workmanship benchmarks.
- First installation area: verify setting out, support, engagement and interfaces.
- Handover: receive as-builts, inspections, maintenance and replacement references.
Common specification mistakes
Avoid these recurring problems:
- Selecting panel size before resolving the elevation grid
- Assuming the outer layer is waterproof
- Accepting tests that do not represent the proposed geometry and fixings
- Applying one wind pressure or fixing pattern to every zone
- Omitting corners, returns and soffits from coordination
- Rejecting normal colour variation without an approved range
- Allowing site cuts without defined limits
- Reviewing fire evidence for materials but not the relevant assembly
- Deferring access and replacement planning
Conclusion
A robust terracotta facade specification connects architectural intent to a buildable, inspectable and evidence-based system. Resolve the module and finish visually, but approve the panels, fixings, subframe and wall interfaces as one coordinated assembly.
Every project-specific structural, wind, seismic, fire and life-safety decision must ultimately be made or verified by qualified professionals and the relevant local authority.