Granny flat slabs
Full raft slabs to engineering for secondary dwellings, including the service set-outs. A steady category across both the Hills and the Hawkesbury.
Concrete slabs & footings
Concrete Slabs & Footings — Hawkesbury & Hills District
A slab is only as good as the ground and steel underneath it. We prepare the site, set out the footings and reinforcement and pour to your engineer’s specification, so it’s ready for the build on top.
- Licensed NSW concreting contractor
- Public liability & home warranty insured
- 13+ years on the tools
- ABN 55 852 128 340
What is the difference between a slab and a footing?
A footing transfers the load of a wall or column into the ground. A slab is the floor. In most residential work the two are combined — a raft or stiffened slab has thickened beams around the edges and under load-bearing lines, so the floor and the footings are poured as one piece.
- WhereHawkesbury, the Hills District and surrounding acreage
- WhatGranny flat, carport, garage and extension slabs, strip and pad footings
- Who does itExcavation, base, formwork, steel and pour by one crew
- Working withOwner builders, builders and developers, to engineering drawings
The complete package
How A Slab Gets Built
The sequence is the same whether it is a carport or a house. What changes is the engineering, and how much of the site has to be rebuilt before it can start.
Set-out to drawings
Working from your engineer or builder’s plans. Dimensions, levels and beam positions marked and checked before anything is dug.
Excavation and base
Site stripped, beams and footings dug, and a compacted base laid. On sloping or filled sites this is most of the job.
Beams and footings
Edge beams, internal beams and pad footings excavated to the depth and width the engineering calls for, not to whatever the ground makes easy.
Membrane and services
Vapour barrier laid and taped where specified, and plumbing, drainage and electrical penetrations set in position before steel goes down.
Reinforcement
Mesh, trench mesh and bar placed to the drawings, on chairs at the specified cover. Cover is the thing that decides whether steel lasts.
Pour, finish and cure
Placed, screeded, finished to the required surface and cured. Levels checked before the crew leaves, because a builder will find every millimetre.
Types
Slabs And Footings We Pour
Shed slabs have their own page — they are our biggest slab category and a different buying decision. Everything else sits here.
Carport & garage slabs
Vehicle-rated slabs with the falls, edge details and thresholds worked out so water runs out rather than in.
Extension slabs
Tying a new slab to an existing building — the fussiest residential slab work there is, with levels, damp and existing footings all to manage.
Strip & pad footings
Footings for walls, posts, columns and piers where the structure does not sit on a slab at all.
Shed slabs
Our largest slab category, covered in full on the shed slabs page — garden sheds through to machinery sheds.
Our standard
What We Build To
On engineered work we build to your drawings. Where there are no drawings — a carport slab, a small extension — this is our own standard, and it is on the quote.
| Design basis | Sites classified under AS 2870, which sets the deemed-to-satisfy footing designs for Class 1 dwellings and Class 10a outbuildings across seven site classes. Where an engineer has issued drawings, we build to those. |
|---|---|
| Inspections | We work in with your certifier or engineer for pre-pour inspection and hold points. Nothing gets poured over unapproved steel. |
Pricing
What Affects The Cost Of A Slab
Two slabs of identical area on neighbouring blocks can differ substantially in price, and almost all of it comes from the ground rather than the concrete.
- Area and shapeSquare metres, plus how much perimeter there is. A long narrow slab costs more than a square one of the same area.
- Site classificationReactive clay under AS 2870 needs deeper beams and more steel than a sand or shale site. Set by the ground, not by the contractor.
- Fall across the siteHow much cut and fill is needed to get to a working level, and whether retaining is needed first.
- Engineering requirementsBeam depths, pier or pile requirements and reinforcement schedules from your engineer.
- ServicesPlumbing and drainage penetrations, conduits and pits set before the pour.
- AccessTruck access to the pour, or the need for a pump and the time that adds.
- Existing structuresTying into an existing building, working around it, or demolishing what is there first.
- TravelDistance to site, which matters on the far Hawkesbury and river jobs.
The technical bit
Site Classification And Why It Decides Everything
If you understand one thing about slab pricing before you collect quotes, make it this.
Seven site classes
AS 2870, the Australian Standard for residential slabs and footings, covers Class 1 dwellings and Class 10a outbuildings such as garages, carports and sheds. It classifies a site into one of seven classes — A, S, M, H1, H2, E or P — based on how much the soil moves as its moisture content changes.
Class A is stable sand or rock. Class P is a problem site requiring custom engineering. Reactive clay sites in the middle of that range need deeper edge beams, more steel and a heavier slab than a stable site does.
This is why a slab quote without a site classification behind it is a guess. It is also why two quotes for the same building can differ by thousands without either being dishonest — they may be pricing different slabs.
Source: AS 2870:2011 Residential slabs and footings, Standards Australia (site classification, Section 2; outbuildings, Clause 1.8). Checked 15 September 2026.
When you need an engineer
For straightforward sites, AS 2870 provides deemed-to-satisfy designs that can be used without a bespoke structural design. Highly reactive and problem sites fall outside those tables and require a structural engineer working directly to the standard.
The standard also notes that residential footing design and construction complies with AS 3600 for concrete, except where AS 2870 takes precedence.
If your job needs an engineer, we will tell you at the quote. We would rather lose a week to a proper design than pour a slab that moves.
Sources: AS 2870:2011 Residential slabs and footings; AS 3600 Concrete structures. Checked 15 September 2026.
Recent work
Slabs We’ve Poured
Why Southo
Why Builders And Owners Use Us For Slabs
We prepare the site ourselves
Excavation, base and slab under one contractor. No handover point for a problem to hide in.
We build to the drawings
Beam depths, cover and reinforcement as specified, not as convenient. Pre-pour inspections respected.
Straight about the ground
If the site needs an engineer, more excavation or retaining first, we say so at the quote rather than as a variation.
Set-outs done before the pour
Services, penetrations and bolt positions in place beforehand, not cut in afterwards.
Works with builders
Used to working to a builder’s program and a certifier’s hold points. Commercial and civil work is on the commercial page.
Licensed and insured
Licensed NSW concreting contractor with public liability and home warranty insurance. Details supplied on request.
Got drawings. Need a price.
Send through the plans and engineering and we’ll come and look at the site.
Reviews
Our Customer Reviews
Service area
Where We Pour Slabs And Footings
Based in the Hawkesbury, working across the Hills, Sydney and the Central Coast.
Questions
Slab And Footing FAQs
Do I need an engineer for my slab?
For a straightforward site, AS 2870 provides standard designs that can be used without a bespoke structural design. Highly reactive and problem sites fall outside those tables and need an engineer. If your site is one of them we will tell you at the quote.
How do I know my site classification?
It comes from a geotechnical investigation, usually arranged as part of the building process. If you do not have one and the job needs one, we will point you to it — it is not something to guess at.
Can you pour a slab for an owner builder?
Yes, and a good share of our slab work is exactly that. We work to your engineer’s drawings and coordinate with your certifier’s inspections.
Do you do the plumbing set-out?
We set out and accommodate penetrations and conduits as part of the slab, working in with your plumber and electrician. The plumbing itself is their trade and has to be signed off before we pour.
What about the vapour barrier?
Where specified, the membrane is laid and taped before the steel. It is a standard requirement on habitable slabs and it is not somewhere to economise.
How long before we can build on it?
It varies with the slab, the weather and the engineering. We give you the date on the day of the pour rather than a rule of thumb.
Can you tie a new slab to an existing house?
Yes. It is fussier than a fresh slab — levels, damp management and the existing footings all have to be worked around — but it is common work for us on extensions.
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Accuracy note
Planning and engineering information on this page is general and was correct at the date checked against the sources named above. Rules change and every site is different — confirm your own situation with Hawkesbury City Council, The Hills Shire Council or a registered certifier. Spotted something out of date? Email southoconcrete2@outlook.com.
