Concrete Slabs in George — Ground Slabs, Suspended Slabs & Surface Beds
Engineered concrete slabs across George and the Garden Route — correct mix design, correct reinforcement, correct curing. We build slabs that don’t crack or settle.
✓ NHBRC enrolled ✓ SANS 10400 compliant ✓ Workmanship guarantee ✓ Fully insured
What We Do
The three slab types we build most often on the Southern Cape.
Ground Floor Surface Beds
Residential and light-commercial surface beds — DPC under, reinforcement to engineer’s spec, concrete to SANS 10100, power-floated or broomed finish. Correct sub-base compaction and moisture barrier.
Suspended Slabs
Engineered suspended slabs — rib-and-block, hollow-core, or in-situ reinforced — installed to the structural drawings. Correct propping, reinforcement placement, and controlled curing for full design strength.
Industrial & Warehouse Slabs
Heavy-duty slabs for workshops, warehouses and commercial yards — engineered thickness, mesh or rebar to load spec, joint layout to control cracking, and power-floated hard-wearing finish.
How It Works
- Engineering and spec. We work to the structural engineer’s spec — or help you get one where there isn’t one. Mix design, thickness, reinforcement, and joint layout all engineered to the intended load.
- Sub-base preparation. Ground slabs live and die on the sub-base. We excavate, compact in layers, verify with plate compactor, and install the DPC and reinforcement before any concrete is called up.
- Ready-mix delivery. Concrete from reputable local suppliers, mix design to match the spec, slump tested on arrival, and cube samples taken where required by the engineer.
- Pour, finish, control joints. Concrete placed and vibrated, screeded to level, floated, and finished to the agreed spec. Control joints cut at the correct spacing to prevent random cracking.
- Curing and protection. Slab covered and kept moist for the required curing period. Foot traffic and loading delayed until the concrete has reached acceptable strength. Handover with the written workmanship guarantee.
Slab Types, and Which One You Actually Need
Ask what types of slab exist and you get a textbook list. On a Garden Route residential or light commercial job, three cover almost everything.
Ground-bearing slabs sit on prepared fill and transfer load straight into the ground. Floors, garages, patios, workshops. The ground carries the load and the slab spreads it, which means the critical work happens under the slab rather than in it.
Suspended slabs span between walls, beams or columns and carry their load in bending. First floors, roof slabs, slabs over basements. These are engineered every time, and the reinforcement design is the job.
Rib-and-block slabs use precast concrete ribs with hollow blocks between them and a structural topping poured over. Lighter, less propping, faster than a solid cast-in-place slab, and the common choice for South African first floors.
Which one you need is usually settled by what is above and below it rather than by preference. Where a slab holds anything up other than itself and the floor finish, an engineer designs it.
| Slab type | Load path | Typical use | Design input |
|---|---|---|---|
| Ground-bearing | Straight into the subgrade | Floors, garages, patios, workshops | Soil assessment; engineer if loads are heavy |
| Suspended, cast in place | Bending, into walls or beams | First floors, roof slabs, over basements | Always engineered |
| Rib-and-block | Bending, via precast ribs | Residential first floors | Supplier design plus engineer sign-off |
Thickness, MPa and Reinforcement Work Together
Three variables decide whether a slab performs, and changing one without adjusting the others is how slabs crack under load or deflect under span.
Thickness governs stiffness and load spread. What pushes it up is rarely the load on top — it is the ground underneath. A slab on poor or variable fill has to bridge soft spots, and bridging is a thickness problem. Adding depth is usually cheaper than a callback.
Strength in MPa is the compressive strength at 28 days. It governs load capacity and abrasion resistance, and — importantly here — density. A stronger mix is a tighter mix, and a tighter mix lets less salt-laden moisture through to the steel.
Reinforcement does almost nothing in compression. Mesh in a ground slab controls shrinkage cracking and keeps any crack that forms tight. Bars in a suspended slab carry the bending load, and their position within the depth is what makes them work.
The single most common failure we find is mesh lying on the subgrade. Steel at the bottom of a slab cracking from the top does nothing at all. Mesh belongs in the upper third, on proper chairs, and it has to stay there while the concrete is placed — dragging it up with a rake during the pour is not a method.
What Goes Under the Slab Decides More Than the Slab Does
By the time concrete arrives, most of the outcome is already fixed. The layers below the slab are where slabs are won and lost, and none of them can be revisited afterwards.
The subgrade is stripped of topsoil and organic material, then made up in compacted layers rather than dumped and levelled. Fill placed in one deep lift consolidates unevenly, and the slab then spans across the soft patches whether it was designed to or not.
Above the fill goes a compacted stone base giving the slab a uniform free-draining bed, then the damp-proof membrane — lapped, taped, turned up at the edges and not punctured. On low-lying erven around Wilderness, Sedgefield and the Great Brak flats, where the winter water table sits high, that membrane and the base thickness are doing real work.
This is also the answer to whether a slab needs waterproofing. A properly installed DPM under a ground slab is the waterproofing, and it has to be right first time. Coating the top afterwards to stop rising damp treats the symptom and usually pushes the moisture out at the wall junction instead.
Joints, Curing and the Coastal Problem
Concrete moves. Joints are where you decide in advance where that movement shows up instead of letting the slab decide for you.
Saw-cut or formed control joints at sensible centres, cut early enough to work, give shrinkage somewhere to go. Isolation joints keep the slab separate from columns, walls and anything else moving independently. Skipping joints on a large pour to save a day is how you get a random crack across a garage floor.
Curing is the other half, and it is the most-skipped quality control on any concrete job. Concrete gains strength by hydrating, and hydration needs water and time. On a windy George afternoon the surface can dry long before the concrete below has finished, leaving a weak, dusty, crazed top layer over sound concrete.
Coastal exposure sharpens all of it — salt air, humidity, strong drying winds and a large day-to-night swing. We plan pours around wind and heat here for the same reason contractors elsewhere plan around rain.
Common Questions
Why do concrete slabs crack?
Three main reasons: poor sub-base preparation causing settlement, inadequate reinforcement or joint layout, or inadequate curing. All three are avoidable. We handle every one — proper compaction, engineered reinforcement, correct joint spacing, and controlled curing.
What thickness should my slab be?
Residential surface beds are typically 85–100mm. Garage slabs 100–150mm depending on vehicle weight. Industrial slabs go 150–250mm and beyond depending on load. The engineer specs the thickness based on actual use — we don’t guess.
Can you match my existing slab level?
Yes — we survey the existing slab or floor level, confirm tie-in elevations, and pour to match. Critical for additions, renovations, and garages tying into the house.
Do you use ready-mix or site-mix?
Ready-mix for anything structural or larger than a small footprint — better quality control, consistent mix design, and delivery times we can plan around. Site-mix only for very small or inaccessible pours.
How thick should a concrete slab be?
For a domestic floor on sound, well-prepared ground, 100 mm with correctly positioned mesh is the usual specification. Garages and driveways typically move to 125–150 mm for vehicle loads, and workshop or light industrial floors start at 150 mm. Poor or variable ground pushes all of those up, because the slab then has to bridge soft spots rather than simply spread load. Suspended slabs are sized by an engineer to suit the span.
What MPa concrete do I need for a slab?
Domestic ground-bearing slabs commonly use 20–25 MPa, with 25–30 MPa typical where there is vehicle traffic, abrasion or coastal exposure. Suspended and structural slabs are specified by the engineer. Near the sea the case for the higher strength is not only load — a denser mix is more impermeable, which slows chloride ingress to the reinforcement.
Do I need mesh in a concrete slab?
In a ground slab, yes in almost all cases — not to carry load but to control shrinkage cracking and keep any crack that forms tight. What matters as much as having it is where it sits: in the upper third of the slab on proper chairs, with adequate laps between sheets. Mesh lying on the subgrade, or hooked up during the pour, contributes essentially nothing.
Why is my new slab cracking?
Almost always shrinkage. Concrete loses volume as it cures and if it cannot shrink freely it cracks; joints and reinforcement manage where that shows and keep the cracks tight rather than preventing them. It becomes a defect when joints were omitted or cut too late, when the surface dried before curing was complete, or when the mesh was in the wrong place. Wide, offset or progressively opening cracks are a different problem and need looking at.
Should a concrete slab be waterproofed?
A ground-bearing slab is protected by the damp-proof membrane installed underneath before the pour, lapped and turned up at the edges. That is the waterproofing and it cannot be redone later, which is why it deserves a walk-through before the concrete arrives. Suspended slabs exposed to weather — a roof slab or a balcony — are a different case and do need a designed waterproofing system over them.
How long before you can build on a slab?
Concrete reaches its specified strength at 28 days, but work usually proceeds before that against the strength actually gained, which depends on the mix and the curing conditions. The more useful answer is that curing should not be cut short to gain a day: a slab that dried out early has a weak, dusty top layer that will wear badly for the rest of its life. We programme the follow-on trades around the curing rather than the other way round.
We Serve George and the Surrounding Towns
Based in George, pouring floor slabs, garage and workshop slabs, patios and suspended slabs the length of the Garden Route.
George · Wilderness · Mossel Bay · Great Brak River · Glentana · Herolds Bay · Sedgefield · Knysna · Plettenberg Bay · Hartenbos · Oudtshoorn · Riversdale
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