Key Decision: Use Visible Fixings for Economy and Direct Access; Use Concealed Fixings for a Hardware-Free Elevation
For a low- or mid-rise facade with smaller repetitive panels, controlled joints and a cost-led brief, start with a visible edge-clip or face-fixed system. For a premium elevation where exposed metal is unacceptable and the project can support factory rear machining, additional rails or hangers, tighter quality control and system testing, start with concealed rear-undercut fixings.
Do not select either family from building height alone. Freeze the architectural intent, provisional panel module, slab thickness, material data and wind zones, then ask the facade engineer to calculate the exact anchor pattern and subframe. This article compares the choices; the facade installation guide owns the installation sequence. For the wider application and supply scope, see Sintered Stone Outdoor Facades.
The Eight-Point Selection Matrix
| Decision factor | Visible edge clip or face fixing | Concealed rear-undercut hanger | Buyer decision |
|---|---|---|---|
| Appearance | Clips, rivets or screw heads remain part of the joint pattern. Colour matching reduces contrast but does not make the hardware invisible. | The panel face remains free of fixing hardware; open joints and panel geometry carry the visual composition. | Use visible hardware deliberately as a repeatable detail, or specify concealed if the design review will reject any face hardware. |
| Required panel thickness | Often available for thinner panels, but the permitted range belongs to the tested clip/fastener and panel combination. | Blind undercut depth, residual material behind the hole and anchor approval set a practical lower limit. Thin-panel options exist, but 6 mm is not an automatic approval. | Ask for a named panel + anchor + embedment combination, not a generic “6–12 mm compatible” statement. |
| Backside machining | Edge-clip systems normally avoid blind rear holes; face-fixed systems require controlled face holes. Edge preparation may still be specified. | Requires accurate blind undercut holes and rear anchors/hangers, preferably under monitored workshop conditions. | If the fabricator cannot document drilling geometry and inspection, do not release a concealed undercut option. |
| Panel replacement | Usually the simplest route to one-panel access because the retaining hardware is visible and direct. | A hook-on panel can be individually replaceable, but only if the rail layout, lift clearance and local access strategy were designed for removal. | Request a one-panel replacement demonstration on the project mockup for either family. |
| Adjustment capability | The subframe can provide alignment and fixed/sliding points; final face position is still governed by the selected clip or fastener geometry. | Hanger systems can add height-adjustment screws and defined fixed/sliding points behind the panel. | Compare the exact system drawings: “concealed” does not automatically mean adjustable, and “visible” does not mean rigid. |
| Cost | Usually lower first cost: fewer machined rear operations and simpler panel hardware. Fischer describes its exposed systems as economical and quick to install. | Usually higher first cost: blind-hole machining, anchors, hangers, extra rails, inspection and engineering coordination. | Price the complete installed square metre, including panel yield, machining, subframe, testing, labour, access and replacement stock. |
| Building height and panel size | Strong starting point for low/mid-rise buildings and smaller repetitive modules. It can also be engineered at height; the wind-zone calculation decides. | Strong starting point for premium mid/high-rise elevations and larger modules when the full system has matching data. Taller buildings may still require smaller panels or more anchors. | Use height as a wind-and-access input, not as a pass/fail rule. Never infer full-slab suitability from the word “concealed.” |
| Final calculation | For both families, the qualified facade/structural engineer responsible for the project must release panel dimensions, thickness, anchor number and position, rails, brackets, structural anchors, movements and safety factors. Manufacturer data supplies inputs; it does not replace the project calculation. | Put the named engineer and required calculation package in the procurement schedule before purchase. | |
Appearance: Decide Whether the Fixing Pattern Is Part of the Elevation
A visible system is not automatically a low-quality detail. A regular clip pattern can work on schools, stations, service buildings and disciplined industrial elevations when the joints, clip finish and panel modules are coordinated. It becomes visually weak when clip spacing changes without reason, hardware colours vary by batch, or the specification promises that colour-matched clips will disappear at close range.
A concealed system removes that hardware from the face, but it does not correct a poor panel layout. Joint width, corner returns, window alignment, cut-panel proportions and batch variation become more visible when the face is clean. Select concealed fixings because the elevation requires a hardware-free reading—not because “concealed” sounds more advanced.
Panel Thickness and Size: Select a Tested Combination, Not a Standalone Number
The market does not support one universal rule such as “visible requires 8 mm” or “concealed requires 12 mm.” Current system documents show why. The Fischer facade systems catalogue separates fixing structures by cladding material, thickness and panel format. Fischer’s current concealed undercut overview includes solutions for thin ceramic panels, while its exposed systems include clamps and face-fixed variants with their own limits.
| Published system example | Published thickness/format signal | What the buyer may conclude | What the buyer may not conclude |
|---|---|---|---|
| Cosentino DKT1 concealed undercut | The current facade manual lists 8, 12 and 20 mm; 12 and 20 mm carry the cited ETA/BBA route in that system table. Full-slab formats are shown as possible. | A rear-undercut system can be designed around several thicknesses and large formats when the named material/system evidence applies. | That every 8 mm slab is certified, or that a full slab is acceptable for every wind zone and support spacing. |
| Cosentino DKT4 visible clip | The same manual lists 4 and 8 mm as standard signals, with 12/20 mm noted, and shows a 1200 × 3200 mm limit for the displayed configuration rather than unrestricted full slab. | Visible clips can suit thin panels and substantial formats within a defined supplier system. | That all visible clips share this range or that 1200 × 3200 mm is suitable on the reader’s building. |
| KEIL concealed undercut family | The system information describes geometry beginning at 6 mm; the material-specific ceramic ETA ties minimum panel thickness to embedment depth and test conditions. | Thin concealed anchoring is technically possible in selected systems, and blind-hole geometry must be controlled. | That an unspecified 6 mm sintered-stone panel is approved for any KEIL anchor, load or facade. |
The Cosentino technical manual also states that thickness suitability must be assessed by the project author and that a competent technician must define and calculate the substructure for each project. That boundary is the correct procurement rule: use manufacturer tables to shortlist, then release only the calculated combination.
For a proposed 6 mm facade panel, the default answer is not “yes” or “no.” The release question is: which named anchor, embedment depth, residual thickness, panel test data and project wind calculation cover this exact combination?
Backside Machining: Concealed Fixings Add a Factory-Control Gate
Visible edge clips normally retain the panel without a blind hole in its rear face. Face-fixed rivets or screws move the machining to controlled holes through the face. Concealed undercut systems instead require blind rear holes whose diameter, depth, undercut geometry, edge distance and residual panel thickness match the anchor data.
This is a selection issue, not an installation tutorial. If the panel processor cannot provide the drilling machine specification, calibrated depth checks, sampling frequency, rejection criteria and anchor traceability, the concealed option is not procurement-ready. KEIL recommends controlled workshop machining for repeatability; Fischer pairs concealed anchors with defined material and thickness ranges rather than treating the anchor as universal.
Replacement and Adjustment Are Separate Decisions
Visible hardware gives the maintenance team direct access, so one-panel replacement is usually easier to explain and price. That advantage matters on schools, transit areas, retail podiums and loading zones where impact damage is plausible. The project still needs an access plan: a visible clip at the joint is not useful if the lift, scaffold or rope-access method cannot reach it.
Concealed does not mean permanently trapped. Rear-anchored panels hung from horizontal rails can be designed for individual removal. Fischer’s horizontal clasp systems include height-adjustment screws on selected top hangers and fixed/sliding-point provisions. The maintenance question is whether there is enough lift and extraction clearance at the actual window, parapet, soffit and corner conditions. Require the mockup team to remove and reinstall one central panel without damaging its neighbours.
Adjustment is also system-specific. Both families can use adjustable brackets and rails to correct the backing wall. Concealed hanger systems often add panel-level height adjustment behind the face; visible edge clips may provide less local correction after their support rails are set. Compare the exact drawing, tolerances and adjustment range instead of assigning the advantage from the fixing name.
Cost: Compare the Installed System, Not the Clip Price
Visible systems normally win first-cost comparisons because the panel package needs less rear machining and fewer concealed components. Fischer describes exposed systems as economical and quick to install. Concealed undercut systems add precision holes, anchors, hangers, horizontal profiles, inspection and a more demanding coordination package.
The correct tender comparison still includes the complete square metre: saleable panel yield after cutting, drilling or face holes, rejected-panel allowance, anchors and clips, vertical and horizontal rails, brackets, structural anchors, engineering, testing, labour, access, mockups, spare panels and the planned replacement method. A cheap clip on a wasteful panel layout can cost more than a better integrated system. Use the separate sintered stone facade cost guide when preparing that full system budget.
Three Project Profiles With a Clear Recommendation
Height, panel module, exposure, access and elevation intent change the preferred fixing family. The three profiles below show where each recommendation leads.
A. Four-Storey School, 8 mm Panels, Repetitive 600 × 1200 mm Module
- Design priority
- Controlled capital cost, rapid enclosure, predictable maintenance and a regular joint grid.
- Exposure
- Moderate inland wind; local impact risk at ground floor; standard mobile access to upper elevations.
- Starting choice
- Visible edge clips.
Use the clip rhythm as an intentional joint detail and colour-match the hardware only after a daylight mockup. The smaller module is compatible with a cost-led visible-system shortlist, and direct hardware access supports future replacement. Separate the ground-floor impact zone if it needs smaller panels, thicker panels or more robust backing. Do not change to concealed fixings merely to remove small clips that the architect has already accepted.
Release condition: a named 8 mm panel/clip system, wind-zone calculations for field/edge/corner areas, confirmed rail tolerances, pull-out data for the structural anchors and a one-panel replacement trial.
B. Twelve-Storey Headquarters, 12 mm Panels, 1200 × 2400 mm Starting Module
- Design priority
- A monolithic mineral elevation with no visible metal and strong alignment around full-height window bays.
- Exposure
- Urban mid-rise; significant corner suction; BMU or mobile-platform maintenance strategy available.
- Starting choice
- Concealed rear-undercut hangers.
The visual brief is explicit enough to justify rear machining, anchors, hangers and horizontal profiles. Start at 1200 × 2400 mm, not the manufacturer’s maximum slab size. Ask the engineer to test whether corner zones need a smaller module, additional anchors or a different rail span. Freeze the undercut anchor and embedment depth before issuing the panel fabrication schedule.
Release condition: matching panel/anchor approval or project test data, blind-hole QC plan, calculated hanger and rail loads, fixed/sliding-point layout, drained cavity details and a full-scale corner-and-window mockup that demonstrates adjustment and central-panel replacement.
C. Thirty-Two-Storey Waterfront Tower, 12 mm Panels, 900 × 1800 mm Starting Module
- Design priority
- Clean long-distance elevation, severe wind exposure, salt-laden environment and permanent rope-access maintenance.
- Exposure
- High corner suction, height-dependent pressure zones, tight access at slab edges and corrosion-sensitive hardware.
- Starting choice
- Concealed undercut only if the complete high-rise evidence package is available; otherwise select visible edge clips with a smaller calculated module.
The tower height does not by itself justify concealed fixings. The premium visual brief supports them, but the technical burden is higher. Begin with a conservative 900 × 1800 mm planning module, marine-grade compatible components and zone-by-zone anchor calculations. A catalogue statement that the concealed family permits “large panels” is not a release for full slabs at upper corner zones.
If the panel/anchor test data, fatigue or cyclic evidence where required, corrosion specification, blind-hole QC and replacement clearance cannot be closed before procurement, do not improvise a hidden detail. A visible system with smaller panels and directly inspectable hardware is the safer procurement recommendation until the concealed package is complete.
Who Owns the Final Calculation and Release?
Architect / specification author
Owns the elevation intent, acceptable hardware visibility, joints, corner language, panel schedule and approved visual mockup. The architect records whether visible clips are an accepted feature or a nonconformance.
Facade or structural engineer of record
Owns design wind pressures by zone, panel thickness and dimensions, anchor number and position, rail and bracket spans, structural anchors, movements, serviceability, safety factors and the final signed calculation package.
Fixing-system supplier
Supplies current system drawings, material and thickness scope, ETA or test values, anchor geometry, fixed/sliding-point rules, adjustment data and calculation inputs. It does not silently extend approval to another panel or thickness.
Panel supplier and processor
Confirms slab identity, thickness tolerance, fabrication limits, hole or edge quality controls, batch traceability, packing and replacement stock. Funtek can coordinate these inputs; final project engineering remains with the contracted qualified designer.
Facade contractor
Coordinates survey data, shop drawings, substrate tests, access, mockups, installation tolerances, inspection records and as-built information. Proposed substitutions return to the engineer before fabrication.
Building authority / appointed reviewer
Accepts the project compliance route required by local law and the contract. Supplier brochures and engineering calculations are submitted in the format required by that reviewer.
The final calculation belongs to the qualified project facade/structural engineer. The panel supplier, fixing-system supplier and contractor provide controlled inputs; none should be allowed to leave the interface between those inputs undefined.
Send a Decision-Ready Fixing Brief
For a useful visible-versus-concealed comparison, send the building location and height, elevation drawings, field/edge/corner wind pressures if available, preferred panel sizes and thicknesses, joint intent, acceptable fixing visibility, backing structure, cavity depth, fire/corrosion requirements, access strategy and the evidence standard required by the engineer. Funtek can then align the panel and fabrication shortlist with the fixing-system data before samples and mockups are ordered.
Use the mechanically fixed sintered stone facade planning to organize the panel, subframe and junction information for the engineer’s review.
Compare a Named Panel and Fixing Combination
Send the facade elevations, provisional module, thickness, wind pressures and appearance brief. We will prepare a panel-and-fabrication shortlist for review with your facade engineer and fixing-system supplier.