GRC and precast concrete panels solve the same problem with opposite economics. Precast is a thick, steel reinforced element that can carry load and form part of the structure. GRC, or glass reinforced concrete, is a thin glass fibre reinforced skin that carries only itself and the wind on its face. The decision between them is settled less often by the rate per square metre than by what the panel weight does to the steel, the fixings, the crane and the install sequence behind it.
The short rule: flat, repetitive and loadbearing favours precast. Curved, detailed, high, heavy-to-reach or weight-constrained favours GRC. The rest of this guide is the detail behind that rule, including the cases where precast is clearly the better answer.
The difference that drives everything: section thickness
A reinforced precast panel needs enough concrete to develop its steel and enough cover to protect it from corrosion, which sets a floor on thickness at around 100 mm and usually more. GRC has no steel, so no cover requirement, and its glass fibre is distributed through the section rather than concentrated in a cage. That lets a GRC panel do a cladding job at 10 to 25 mm. ShapeShift’s ShapeShell-RC panels run 15 to 25 mm. Panel sizes, weights and fixing options are set out in GFRC panels: sizes, thickness, fixing and cost, and the three ShapeShell substrates are compared in FRP vs GRC vs GRG.
Every other difference in this comparison follows from that one. Thickness sets weight, weight sets the supporting structure, and the supporting structure sets most of the installed cost.
Weight, and what it costs downstream
ShapeShift rates ShapeShell-RC at around 50 per cent lighter than precast concrete. The panel supply saving from that is the least interesting part. The consequences sit in other trades:
| What changes with a lighter facade | Effect |
|---|---|
| Supporting steel or framing | Sized for a smaller dead load, so lighter sections and fewer of them |
| Fixings and brackets | Smaller, cheaper, faster to install, with less penetration of the backing wall |
| Crane class and hire period | Smaller crane, or the same crane reaching further, or fewer lifts |
| Slab edge and transfer conditions | Less load to resolve at the slab edge on a tower |
| Retrofit and overclad | Often the only viable option, because the existing structure cannot take precast |
| Transport | More square metres per truck, which matters on any job feeding from one factory |
This is why the material comparison is the wrong comparison. On a tower, halving facade mass changes the steel schedule, the fixing count, the crane class and the installation sequence at once, and those line items usually exceed the difference in panel rate.
Structural role: cladding against structure
Precast can be loadbearing. A precast panel can be the wall, carry floors and brace the building, and on the right building that removes a whole frame. GRC cannot do any of that. It is a cladding material, engineered to carry its own weight and the wind load on its face and transfer both into a supporting structure.
If the design intends the panel to be the structure, the comparison ends here and the answer is precast. If the building already has its structure and the panel is a skin, GRC is in play.
Geometry and moulds
Both materials are cast against a mould, so both can take shape. The difference is what shape costs.
A thick precast element in double curvature needs a heavy mould, careful reinforcement placement and a large volume of concrete in an awkward form. A thin GRC skin in the same geometry is sprayed into a lighter mould, in layers, with fibre orientation controlled between passes. Deep relief, perforation, single and double curvature are routine work in GRC and expensive work in precast.
In both cases the cost driver is the number of unique moulds, not the area. Twenty panels off one mould is a different job from twenty panels off twenty moulds. Panel type rationalisation early in design is the largest single lever on either material, and it is usually available without changing how the building looks.
Fire and compliance
Both are cement based and both are non-combustible, so neither carries the compliance risk that ended the use of polymer-cored composite panels in Australia. GRC is classified non-combustible when tested to AS 1530.1, and independently tested data for ShapeShell-RC covering combustibility, reaction to fire, heat and smoke release and ignitability is published on the material fire rating page.
Two things to hold onto. First, fire compliance is assessed on the whole wall assembly, including backing wall, supports, insulation, cavity treatment, fixings, sealants and coatings, not on the panel in isolation. Second, the evidence that matters is the test report matched to the product supplied, not the word “non-combustible” in a brochure. That applies equally to both materials. The NCC requirement itself sits in clause C2D10, which applies to buildings required to be of Type A or Type B construction and reaches the facade covering, framing and insulation rather than the panel alone. Which NCC edition applies now varies by state, and both points are set out in non-combustible facade cladding and what the NCC requires.
Where precast has a genuine edge is fire resistance level. A thick concrete element can achieve an FRL and act as a fire separating element. A thin GRC skin is non-combustible but is not an FRL rated wall on its own, so where the design needs an FRL the rating comes from the backing wall behind the GRC.
Finishes
Precast offers the full range of concrete finishes: acid wash, sandblast, polished, and stone bonded to the face. GRC offers those plus through-pigmented colour in the mix, coatings including fluoropolymer and gel coat systems, textured mould faces, and stone facing at a fraction of the installed weight. ShapeShift’s range is on the colour and surface finish page.
Two practical notes. Because GRC colour can run through the full section, a chip or a drilled penetration exposes the same colour rather than a grey substrate, which matters on any facade where access is expensive. And on both materials, colour consistency across a large elevation is a manufacturing quality question, so ask how many panels come off one mould before it is replaced, and ask to see panels from two different batches side by side.
Transport and installation
Precast is heavy, which limits panels per load and dictates lifting equipment at both ends. GRC gets more square metres onto a truck and into a container, which is what makes a single factory viable across multiple states or countries.
On site the difference shows up in crew size, lift rate and access. Lighter panels can often be installed from inside the slab edge, or with smaller plant, or in locations a crane cannot reach economically. On a constrained inner-city site that can be the deciding factor before cost is discussed.
Lead time and programme
For both materials the long pole is mould fabrication and shop drawing approval, not casting. What differs is flexibility. GRC moulds are lighter and faster to build and to modify, so a late design change is usually cheaper to absorb. Compressing delivery on either material means building more moulds to hold the production rate, which is a direct cost rather than a scheduling trick.
Where the programme is very tight and the geometry is simple, stock sizes remove the mould question altogether. ShapeShift holds standard GRC facade panels in set sizes for exactly that case. Lead times depend on tooling, panel count and finish, and are confirmed at quotation.
Cost: where the money actually is
Comparing a GRC rate to a precast rate answers the wrong question. The comparison that decides projects is the installed cost of the facade system, which is:
- Panel supply
- Supporting steel or framing, sized for the panel dead load
- Fixings, brackets and their engineering
- Transport, including how many panels per load
- Cranage and lifting plant, including hire duration
- Installation labour and the rate of install
- Programme effect, including how long the crane and the crew are on site
- Whole-of-life maintenance and the cost of access to do it
Run those eight lines for both materials on the actual elevation and the answer is usually unambiguous, and it is not always GRC.
When precast is the right answer
Precast wins, and should be specified, when:
- The panel needs to be loadbearing or to brace the structure
- The wall needs a fire resistance level in its own right
- Elevations are flat and highly repetitive at volume, where mould economics favour thick panels and the weight penalty is small
- The element is heavy civil: retaining, culverts, barriers, structural floors
- Mass or acoustic performance is part of the design intent
- The structure is already sized for the load and the site has easy crane access
When GRC is the right answer
GRC wins when:
- Weight is constrained, by a tower’s slab edges, a transfer structure, or an existing building in a retrofit or overclad
- The facade has curvature, deep relief, perforation or non-repeating geometry
- Access is difficult or crane time is expensive
- Panels ship a long way, including across states or from offshore
- The design wants a concrete appearance without the structural consequences of concrete
- The element is sculptural, as in public art and feature fabrication, covered under public artwork
A seven question decision checklist
- Does the panel need to carry load or brace the structure? If yes, precast.
- Does the wall itself need an FRL, or can the backing wall provide it?
- How many unique panel types does the current design create, and can that be reduced?
- Is any part of the elevation curved, perforated or deeply modelled?
- What does the structural engineer say the facade dead load allowance is?
- What crane and access is available, and for how long?
- How far do the panels travel, and how many fit on a load?
Answers to one, two and five usually decide it on their own.
Project evidence
The weight argument on this page is not theoretical. On these projects it changed the building.
- Queens Domain: a lightweight slab edge treatment, designed with the structural engineers before the structure was set, let the slabs be thinned. Over 20 storeys that bought the building a whole extra level inside the same height limit.
- Royal Randwick Racecourse: the facade was originally specified in concrete and the weight of 5,500 discs exceeded what the car park structure could reasonably carry. The lighter equivalent made the design buildable as drawn.
- Marina Concourse: tapered columns, which are one of the least economical things to cast because the formwork changes with the taper.
- Oasis Apartments: slab edge panels on a multi-storey residential building, the point on any floor plate least able to carry load.
Frequently asked questions
Is GRC cheaper than precast?
Not reliably on panel rate, and frequently yes on installed cost, because a lighter facade reduces supporting steel, fixings, cranage and install time. The comparison is only meaningful on a specific elevation with those items priced.
Is GRC as strong as precast concrete?
It is much stronger than unreinforced concrete in tension and bending, which is what allows thin-wall casting, but it is not a substitute for a structural precast element. GRC is engineered as cladding.
Can GRC replace precast on an existing building?
This is one of GRC’s strongest cases. Overcladding often fails on precast because the existing structure cannot accept the added dead load, and a thin non-combustible skin can.
Do GRC and precast look different?
Not necessarily. GRC panels can be finished to read as precast, including through-colour, acid wash, sandblast and stone facing. The difference a specifier notices is in the joints and the depth of reveal available at thin section.
Which has the longer service life?
Both are long-life materials. The most common deterioration mechanism in a precast facade is corrosion of the reinforcement and spalling at the cover zone, which does not apply to GRC because there is no steel. GRC’s service life is governed instead by the fibre specification, the coating where one is used, and the joint and fixing detail. Warranty terms are confirmed at quotation and depend on the panel and the coating specified.
Getting a real answer for your project
For a live facade package, send the elevations, the structural dead load allowance and the nominated compliance pathway rather than a request for a rate. That is enough for ShapeShift’s engineers to come back on panel type rationalisation, fixing approach, fire evidence and programme, and to say plainly where precast would serve the project better. Start at contact, see built work in the project archive, or read the material background in what is GRC.
Terms explained
Short definitions of the terms on this page, in our facade materials encyclopedia.
