A flat block makes fencing easy. A sloping one raises the question every DIYer asks at the string-line stage: how do you keep the fence looking neat when the ground falls away beneath it? The good news is that Colorbond fencing handles slopes well — you just need the right method and a few components prepared differently. This guide covers both approaches and the exact measurements for a clean result.
Stepped vs Raked: Which Should You Choose?
There are two ways to run a fence downhill, and the difference matters:
Stepped panels stay horizontal and drop down in steps as the ground falls, leaving triangular gaps under each panel. It’s simpler to set out but leaves gaps that need filling, and the stepped look isn’t for everyone.
Raked panels follow the slope of the ground, with the rails and infill sheets angled to match. ClickSteel recommends raking over stepping wherever possible — it achieves a better finish and a stronger fence, with no gaps underneath.
For gentle to moderate slopes, raking is almost always the better call. Very steep or terraced blocks are where stepping (or a mix, with plinths filling gaps) earns its place.
Handling Small Rakes: No Rail Change Needed
Here’s a detail that saves a lot of over-ordering: small rakes of less than 150mm do not require any increase in rail length. For these gentle slopes, the standard 2365mm rail works fine — you simply adjust the infill sheet cuts to suit.
As the rake increases, the infill cut height changes on a predictable scale. Using the standard 2365mm rail:
| Rake height (Y) | Infill cut height |
|---|---|
| 150mm | 50mm |
| 200mm | 67mm |
| 250mm | 83mm |
| 300mm | 100mm |
| 400mm | 133mm |
The formula behind it is simple: the total rake (Y) is divided by the number of infill sheets in the panel to give the cut per sheet (X). With three sheets per standard panel, a 300mm rake means each sheet is trimmed by 100mm across its angle.
How to Cut Infill Sheets for a Raked Panel
Getting the angle right is the whole game. The method:
- Place a spirit level inside the rail at the high end.
- Measure across the width of one sheet, then measure the height from the bottom of the level down to the inside of the rail. This gives you the angle of the cut.
- Match the top rail angle to the bottom rail where possible. You can adjust the top rail angle if you prefer — just remember it raises the post height, so allow for that when setting posts.
- Cut all three infill sheets together. Stack them, measure edge to edge, and cut once — this guarantees every sheet matches and the panel looks uniform.
Vertical Slitting on Steeper Slopes
On slopes steeper than 1:8, the rake can reduce the three-sheet coverage to the point where one sheet needs vertical slitting (a lengthways trim). On Colorbond and Zincalume sheets this is done cleanly with a straight edge and tungsten-tipped hand cutters — score the line, then bend and snap the sheet. Avoid anything that throws hot metal filings onto the coating.
Don’t Forget the Post Heights
Raking changes your post maths. Because the fence rises along the slope, and matching the top rail angle can add height, posts on a raked run often need to be longer than on a flat run. Work out your required post length before ordering — our step-by-step Colorbond fence installation guide explains the footing-plus-height calculation, and the DIY fence kit cost breakdown helps you budget the extra.
Filling Gaps With Plinths
Where you do end up stepping — or where the ground is uneven under a raked panel — plinths are the neat fix. They fill gaps beneath the fence and can retain low volumes of soil, stacking from 155mm for a single plinth up to 595mm for five. Note that when stacking more than one plinth, a heavier SHS post is needed between the standard posts to strengthen the run.
Ready to Tackle Your Sloping Block?
Sloping sites reward a bit of planning, but they’re well within reach for a confident DIYer. Choose your method, get the infill cuts right, and order the correct post lengths from the start. Browse Colorbond fence kits with instant online pricing, and explore the full COLORBOND® fencing colours range. Call us for any further assistance.