So you’re planning a build out in the backyard?
Whether it’s a shed, carport, granny flat or workshop. Whatever you build, the actual construction is only part of the process. Preparation you do prior to laying the first bag of concrete determines success or failure.
Skip it and you’ll regret it.
The best news? Prep isn’t hard. Just some advanced planning and diligence.
In this guide you’ll learn the essential preparation steps that every outdoor build should go through – Including those that most people get badly wrong.
Here’s what’s coming up:
- Why Prep Work Matters
- How To Assess Your Site
- Why Foundations Make Or Break The Build
- Council Approvals You Can’t Skip
- Marking Out, Tools And Timing
Why Prep Work Matters More Than You Think
Most outdoor builds fail because of one thing.
Poor preparation.
A survey found that 45% of homeowners have botched a DIY project by jumping in without proper planning. And the statistics are even uglier when you consider concrete alone.
The American Concrete Institute says 85% of concrete failures are caused by poor subgrade preparation. Cracked slabs, sinking pads, heaved edges… 90% of it can be linked back to preparation that was rushed or omitted.
Bottom line: what’s underneath your build matters more than the build itself.
Translation? Prep work is the highest-ROI time you’ll spend on the whole project.
Foundations First: The Reinforced Concrete Slab
Sheds, Garages, workshops & Carports – your best option for foundations is a reinforced concrete slab. It’s solid as a rock, will likely outlive you and prevents rising damp. It will also provide you with a level, dry base to build on – allowing you to fix walls and frames to it. Simplifying the build process.
And here’s the truth bomb… This is also the piece of the project that is the most difficult to redo. Therefore proper execution is even MORE important than anywhere else.
But not all slabs are equal.
If you need a concrete shed floor, you have to consider thickness, mesh, edge support and curing. A slab for a flat tin shed compared to a slab designed to support vehicles are two very different projects.
A solid reinforced concrete slab should include:
- A compacted base layer (100-150mm of crushed rock)
- A plastic membrane to block ground moisture
- Steel mesh reinforcement (SL72 or similar for shed floors)
- 100mm minimum thickness for most sheds
- Thickened edges for load support
Skip any of these and you’re rolling the dice on the slab’s lifespan.
Step #1: Assess Your Build Site
Walk and look before you dig and pour.
You need to know about:
- Slope – is the ground level or sloping?
- Soil type – clay, sand, loam, or rocky?
- Drainage – where does water flow after heavy rain?
- Access – can a concrete truck or trailer get in?
- Underground services – any pipes, cables, or stormwater?
Clay soils are a nightmare. They swell when they get wet and shrink when they dry. That movement moves your slab around. If you have clay soil, you’ll need a deeper engineered base under your concrete slab. You may even want to do a soil test prior to pouring if you plan on building something heavy.
Poor drainage is equally dangerous. Standing water around your build will erode the base eventually. Resolve all water problems prior to building, not after.
Step #2: Check Your Council Approvals
Boring? Yes.
Avoidable? Not really.
A lot of people mess this up and get fined heavily.
Most councils will have regulations around what you can and can’t build without a permit. Size, height, set back distances from boundaries, easements, bushfire or flood overlays…the list goes on.
Things to check before you start:
- Whether you need development approval
- Setback distances from your boundaries
- Maximum allowed height for your structure
- Stormwater and drainage requirements
- Bushfire or flood overlay restrictions
You can be fined thousands for unauthorised building work – even have it demolished. Five minutes on the phone to your council will save you from heartache and money.
Step #3: Mark Out The Build Area
Once you know what you’re building and where, it’s time to mark it out.
Few steps are more important than this one. Layout your project’s footprint with stringlines, nails, and spray paint. Recheck your measurements twice before making them permanent.
One report revealed that 47% of DIYers misjudge how long a project will take and 38% don’t bother with precise budgets – and many of those issues begin when you’re marking-out and measurements are incorrect.
Spend a few minutes with a string level or laser level now and you’ll save hours of cutting and packing later.
Do the framing right and everything else falls into place. Frame it wrong and you’ll be pulling things out to do over.
Step #4: Have All Tools And Materials Ready
Nothing kills momentum like running out of supplies halfway through a concrete pour.
Make a comprehensive checklist of everything you’ll require. Tools, fixings, concrete, reinforcement, shuttering timber, sealant, hire equipment – everything.
Common items you’ll need for a slab pour:
- Shovels and rakes
- Plate compactor (hire one)
- Bullfloat and screed
- Vibrating poker for thicker pours
- Curing compound, or hessian and water
Buyout the entire site before mixing or ordering concrete. Concrete does not stop for anyone.
Step #5: Time The Build Around The Weather
Weather makes or breaks an outdoor build.
This is the bit DIYers love to ignore – and then pay for.
Don’t want to pour a slab when it’s raining heavily or in the middle of a heatwave. Either can adversely affect the cure and cause a weaker finished product.
Ideal pouring conditions:
- Temperature between 10°C and 25°C
- Light cloud cover (no harsh direct sun)
- No rain forecast for 24-48 hours
- Low wind
Look at the forecast all the way through the week before you pour. If it looks questionable, reschedule the pour. You don’t want to ruin the whole slab over a few days.
Bringing It All Together
Prep work isn’t the fun part of any outdoor build.
HOWEVER, it’s the durability factor that determines if your project will last 5 years…or 50. If you forego preparation, your build will be a never ending maintenance cycle. Prepare correctly and you can put the slab out of mind for the next 50 years.
To quickly recap, before any outdoor build you should:
- Plan a proper reinforced concrete slab foundation
- Assess your site (slope, soil, drainage, access)
- Check council approvals and permits
- Mark out the build area accurately
- Have all tools and materials ready on site
- Time the build for good weather
Get these six things right and the actual build becomes the easy part.
Cut corners on any of them and you’ll be paying for it for years.
