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Guide

How to Measure Up Sliding Gates on Raked Ground

Updated · ~14 min read

Two ways to build a sliding gate over raked ground. Match the rake with a parallelogram-shaped panel, or keep the panel rectangular and live with a wider gap at the low end. The single most common mistake is measuring at the closed position only and missing the rake along the runout.

TL;DR

  • Two design approaches: raked bottom rail (gate matches the ground) or level rail with extra clearance at the low end.
  • Raked-rail wins on aesthetics, takes longer to build, and needs every batten cut to a different length.
  • Level-rail wins on cost and rolling action, but the under-gate gap grows visibly at the low end.
  • Cantilever gates handle rake better than tracked sliders. The structural rail stays straight; only the panel below it follows the rake.
  • Measure five points across the runout, not just the closed position. Most install failures trace back to a single-point measurement.
  • Aim for 30 to 50 mm ground clearance at the closest point along the gate’s full travel.

What ‘raked’ means and why it matters

Rake is just a slope. Australian builders call it rake; surveyors call it gradient or fall. They all describe the same thing: ground that rises or falls along a defined direction. Quote it as a ratio (1 in 50 means 20 mm of rise per 1000 mm of run) or a percentage (1 in 50 is 2%).

A swing gate over rake is easier than a sliding gate over rake. The swing gate hinges at one fixed point. The leading edge sweeps an arc through the air, well clear of the ground. As long as the swing radius doesn’t intersect the ground at any point in its travel, the gate works.

A sliding gate has to clear the ground along its entire travel. Imagine a 4 m gate sliding 4 m sideways: every point on the bottom rail passes over every metre of ground in the runout. If the ground rises by 30 mm halfway along the runout, the bottom rail had better be at least 30 mm higher than the gate-closed clearance. If you don’t plan for it, the gate jams. See the sliding gate and cantilever gate glossary entries for the underlying mechanics.

Three rake scenarios

Three ways the ground rakes relative to a sliding gate. Each behaves differently and has its own design call.

Scenario 1: Cross-fall

HighLowGate panel (level rail)Cross-fall: gap grows toward the low end

Cross-fall is rake across the opening, perpendicular to the gate’s travel. Common around pool surrounds where the deck is graded toward a drainage line. The gate panel itself runs perpendicular to the slope. Cross-fall translates to a side-to-side height difference along the gate width but doesn’t move along the runout. A level-rail gate ends up with a 30 mm gap at one end and a 60 mm gap at the other.

Scenario 2: Long-fall toward the runout

ClosedRunoutClosed positionOpen (rises into runout)

The ground rises as the gate slides open. Common on driveways with a downhill kerb at the front. The gate-closed end sits over the lower ground; the runout end sits over the higher ground. Critical detail: the bottom rail at the runout end has to clear the ground at every point along the runout. If the rake is steep, the bottom rail may need to be 60 mm above ground at gate-closed but 100 mm above ground at the runout end.

Scenario 3: Long-fall away from the runout

ClosedRunoutClosed positionOpen (falls into runout)

The ground falls as the gate slides open. The trickiest of the three because the bottom rail and the rollers can drift apart in alignment. With a tracked V-track running level (or worse, running uphill against the rake), the rollers want to be on a different plane to the bottom rail. The gate ends up rocking on the rollers and clattering at every cycle. The fix is a cantilever gate where the structural rail stays straight regardless of ground.

The two design approaches

Approach 1: Raked bottom rail

Build the gate panel as a parallelogram. The top rail stays level (parallel to the level top of the fence run). The bottom rail follows the ground rake. Battens or slats are cut to varying lengths to span between the two non-parallel rails.

Pros: tight, even ground clearance along the full runout. The gate looks ‘right’ against the ground. No visible wedge gap at one end.

Cons: every batten or slat is a unique length. Workshop cutting time roughly doubles. The bottom-rail-to-stile joint is no longer a clean 90 degrees, so mitre cuts go up in complexity. Cantilever rail (the structural top of a cantilever gate) must still stay straight, so a raked-rail cantilever gate has a level cantilever rail above the raked panel, with a small triangular spacer between them.

Approach 2: Level bottom rail

Keep the gate panel as a clean rectangle. Top rail level, bottom rail level. Set the gate height so the bottom rail clears the high point of the rake by the standard 30 to 50 mm. Live with the larger gap that opens up at the low end.

Pros: standard rectangular fabrication. Every batten cut to the same length. Mitre joints stay 90 degrees. Easier to roll because the bottom rail and any track or rollers stay parallel.

Cons: under-gate gap grows visibly at the low end. On a 4 m gate over a 1 in 30 cross-fall, the gap goes from 30 mm at the high end to 130 mm at the low end. That’s a security and aesthetic call, not just a fabrication choice. For pool gates the larger gap may also breach the AS1926.1 100 mm rule at the low end if the gate runs over the non-climbable zone.

Step-by-step measurement procedure

The procedure below uses five measurement points across the gate’s full travel, not the standard two (post centres only). Five points catches the rake in every direction and flags any intermediate dips a regrade missed.

Tools

  • Tape measure, 8 m or longer.
  • Rotary laser (preferred) or 4 m straightedge plus spirit level.
  • Marker spray or chalk for ground marks.
  • Notebook (paper still beats phone in a workshop).

Step 1: Establish a level datum

Set up a rotary laser sweeping a horizontal plane across the full gate runout. The laser line is your datum. If you don’t have a laser, stretch a string line between two stakes and level it with a spirit level. Mark the datum height clearly on each post (or fence post if there are no gate posts yet).

Step 2: Take five height measurements

Measure the ground height below the datum at five points: the catcher post, the gate-closed midpoint, the runout end, and two intermediate points spaced evenly between them. For a 4 m gate with 5 m of runout, the points sit at 0, 1.25, 2.5, 3.75, and 5 m. Record all five numbers.

Step 3: Calculate the rake angle

Subtract the lowest measured height from the highest to get the rise. Divide by the runout length to get the gradient as a ratio (1 in N) or a percentage. For example, 60 mm of rise over 5000 mm of run is 1 in 83 or 1.2%, which is a small rake. 100 mm of rise over 4000 mm is 1 in 40 or 2.5%, which is significant.

While you’re at it, scan for intermediate dips. If the midpoint reads lower than both ends, the ground isn’t a clean linear slope; it has a saucer in it. That changes the design call.

Step 4: Decide which design approach

Three quick rules.

  • Under 1 in 50 (2%) rake: level bottom rail. The under-gate gap variation is small enough that no one notices.
  • 1 in 50 to 1 in 30 (2 to 3.3%): aesthetic call. Pick raked bottom rail if the gate is a feature of the front fence (street-facing slatted or battened build). Pick level bottom rail if cost matters more.
  • Steeper than 1 in 30 (over 3.3%): raked bottom rail or regrade. A level-rail gate at this rake gets ugly fast.

Step 5: Verify clearance at every point

For your chosen approach, work out the bottom-rail height above the ground at every measured point. Confirm it stays in the 30 to 50 mm target range across the full travel. If a point drops below 30 mm, the gate jams on debris. If a point rises above 80 mm, you have a security gap. Adjust the design (raise the gate, switch approaches, regrade) before fabrication starts.

Cantilever vs tracked sliders on rake

Cantilever and tracked sliding gates handle rake very differently. Worth knowing before you spec the build.

Cantilever sliding gatesride on top rollers fixed to the receive post. The cantilever rail (the heavy structural section running the gate’s full length) stays whatever shape it was welded as, irrespective of the ground below. So a cantilever gate can carry a raked bottom rail without affecting roller alignment, as long as the structural cantilever rail itself is welded straight. This makes cantilever the natural choice for raked sites.

Tracked sliding gates are more constrained. The V-track or U-track must stay either dead level or run a smooth slope. Bottom rollers run perpendicular to the rail face. If the panel above is parallelogram-shaped (raked bottom rail) but the track is level, the rollers and the bottom rail are no longer parallel and the gate rocks at every cycle. Above about 1 in 60 (1.67%) long-fall, switch to a cantilever and stop fighting the track.

Worked example: a 4 m cantilever gate over a 60 mm cross-fall. The cantilever rail is welded straight. The bottom rail is welded raked, parallel to the ground line, dropping 60 mm across the 4 m gate width. Battens are cut to fit between the two rails and read as a clean rhythm of varying heights. Top rollers on the receive post handle the gate weight; the rake under the bottom rail is invisible to the roller mechanism.

Common mistakes

  • Measuring at the gate-closed position only.The gate doesn’t live at the closed position. It travels the full runout every time it opens. A two-point measurement (post centre, post centre) misses every metre of ground in between.
  • Forgetting future driveway re-paving.Resurfacing typically lifts the driveway by 30 to 50 mm. A new gate at 70 mm clearance becomes 30 mm clearance after the next overlay, which is the floor of the workable range. If the customer says ‘we’re re-doing the driveway in three years’, build at 100 mm.
  • Specifying a cantilever rail at an angle.The cantilever rail is the structural fulcrum the gate hangs off. If it’s welded at any angle other than straight along its length, the top rollers fight it on every cycle. Fab the cantilever rail straight; rake the bottom rail and battens below it instead.
  • Mounting the gate motor pad on rake. The motor pinion runs in a horizontal plane and meshes with the drive rack on the gate. If the motor pad sits on rake, the pinion-to-rack mesh angle is wrong and the gear runs noisy and wears fast. Pour the motor pad level even if the rest of the driveway is raked.
  • Setting up a level-rail gate with too small a clearance at the low end. A 30 mm gap at install becomes a 0 mm gap on a hot summer day when the steel expands. Workshop steel grows about 1 mm per 100 mm length per 30 degrees C of temperature change. A 4 m gate that was 30 mm clear in winter is jamming at noon in February.
  • Ignoring intermediate dips.The two end heights tell you the rake, but they don’t tell you about a saucer or a hump in the middle. Five points catches them. Two points doesn’t.

Generate a sliding-gate drawing for raked ground in 60 seconds

Pick a sliding-gate model below, enter your opening width and your raked left and right heights, and CAD60 generates the dimensioned A4 drawing pack. Battens or slats get cut to length per row, the bottom rail follows the rake, and the cutting list reflects every unique length needed.

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Frequently asked questions

How much rake is too much for a sliding gate?

About 1 in 50 (20 mm of rise per 1000 mm of run) is the practical ceiling for a level-rail sliding gate before the gap at the low end becomes ugly or unsafe. Past that you go to a raked bottom rail, or you regrade the driveway. Cantilever gates handle rake more gracefully than tracked sliding gates because the cantilever rail itself stays straight.

Should I level the driveway before installing a sliding gate?

If the rake is over 1 in 30, regrading is usually cheaper than a custom-fabricated raked-rail gate over the next 20 years of maintenance. Below 1 in 50 the rake is small enough to absorb in ground clearance. The middle band (1 in 50 to 1 in 30) is the awkward zone where you weigh fabrication cost against driveway works cost.

Does a cantilever gate work on raked ground?

Yes, and better than a tracked slider. The cantilever rail rides on top rollers fixed to the receive post. As long as that cantilever rail is welded straight, you can rake the bottom rail and infill below it without affecting the rolling action. Tracked sliders have to keep the V-track on a smooth slope or level, which constrains site fit.

What's the minimum ground clearance under a sliding gate?

Aim for 30 to 50 mm at the closest point along the gate's full travel. Under 30 mm and the gate jams on debris, leaves, and minor frost heave. Over 80 mm and you have a security gap (a child or pet can crawl under) plus an unsightly view straight under the gate face.

Can a tracked sliding gate handle a slope?

Only a smooth, single-direction slope along the gate's travel, and the V-track must follow the slope at the same gradient. Cross-fall, dips, and irregular ground all make tracked sliding gates fail. Above about 1 in 60 long-fall, switch to a cantilever and stop fighting the track.

Should the bottom rail of a sliding gate be straight or follow the rake?

Two valid answers. Straight (level) is simpler to fabricate, easier to roll, and accepts a wider gap at the low end. Raked matches the ground for a tighter, cleaner look, but the gate panel becomes a parallelogram, infill battens vary in length, and the build is more expensive. Pick straight unless the gap looks wrong.

How do I measure rake without a builder's level?

A 4 m straightedge plus a spirit level works for short runs. Lay the straightedge on the ground, level it, and measure the gap underneath at the low end. That gap divided by the straightedge length is the rake. For runs over 4 m, hire a rotary laser. They're $150 a day and the only reliable way to take five points across a 6 m runout.

Will an automated gate motor work on raked ground?

The motor pad has to be level. The gate can be raked, but the motor itself runs a horizontal pinion that meshes with the drive rack on the gate. Pour the motor pad on the level, set the rack height to match the rake of the gate's bottom rail, and the geometry works.

What's the maximum cross-fall allowed at a pool gate runout?

There is no hard cross-fall limit in AS1926.1. The standard cares about the barrier's height, gap, and self-closing/latching, not the ground beneath the runout. But be careful: cross-fall under a pool gate often reduces the effective height (you measure from the lowest non-climbable surface), and you can lose your 1200 mm minimum at the downhill side without realising.

How do I plan for future driveway re-paving?

Resurfacing typically lifts the driveway by 30 to 50 mm. Build that allowance into your ground-clearance number now. A new gate at 70 mm clearance over a 20-year-old driveway becomes 30 mm clearance after the next overlay, which is the floor of the workable range. Build at 100 mm if a re-pave is expected within five years.

References & related