Gate Installation Guide
How to Measure for a Garden Gate
Accurate measurements are essential when choosing or fitting a garden gate. This guide explains how to measure the opening, allow for posts, hinges and clearances, and record the details needed before ordering.
In this guide
Before You Measure
Before taking any measurements, decide where the gate will be fitted and what type of gate is required.
You will normally need:
- Tape measure
- Spirit level
- Notepad or phone
- Straight edge
- A second person for wider openings
- Photographs of the opening and surrounding area
Before starting, check:
- Whether the gate will fit between posts, walls or a combination of both
- Whether new posts are required
- The preferred opening direction
- Ground levels and slopes
- Nearby fences, walls, steps or paving
- Whether the gate needs to match an existing fence
- Whether there is enough space for the gate to open fully
Measure the opening in more than one place, particularly where posts or walls may not be perfectly vertical.
Identify the Gate Opening
The gate opening is the clear space between the two supporting points.
These may be:
- Two timber posts
- Two concrete posts
- Two metal posts
- A wall and a post
- Two walls
- Existing gate posts
- New posts that still need to be installed
Do not measure only the old gate itself. Measure the full opening and record what is supporting each side.
Also note:
- Which side will carry the hinges
- Which side will carry the latch
- Whether the supports are vertical
- Whether either support moves
- Whether the opening narrows at the top or bottom
- Any obstructions such as pipes, walls or raised paving
Photographs taken from both sides are useful if you need advice before ordering.
Measure the Opening Width
Measure the clear width between the supporting posts or walls.
Take measurements at:
- The top
- The middle
- The bottom
Use the smallest measurement when checking whether a gate will fit.
For example, an opening may measure:
- 930mm at the top
- 925mm in the middle
- 918mm at the bottom
In this case, the smallest opening is 918mm.
Do not assume an opening is square simply because the existing gate fits.
Also check whether the posts or walls lean inward or outward.
Measure the Required Height
Measure from the planned bottom of the gate to the required finished height.
Allow for:
- Ground clearance
- Paving or finished surface
- Sloping ground
- Gravel boards
- Fence-panel height
- Decorative tops
- Posts extending above the gate
The gate normally needs a small clearance beneath it so it can open without dragging on the ground.
The required clearance depends on:
- Whether the surface is level
- Whether the gate opens over grass, soil or paving
- Seasonal ground movement
- Leaves, gravel or debris
- The direction of any slope
Measure the required height on both the hinge side and latch side.
Allow for Posts
Gate posts must be strong enough to support the gate and the movement created when it opens and closes.
If new posts are needed, record:
- Post material
- Post width and thickness
- Post length
- Foundation depth
- Gate weight
- Gate width
- Wind exposure
The hanging post is particularly important because it carries the gate’s weight.
A lightweight pedestrian gate may be suitable for a standard timber gate post, while larger or heavier gates may need:
- Larger timber posts
- Purpose-designed metal posts
- Heavier foundations
- Additional bracing
- A pair of substantial driveway gate posts
Do not assume that a standard intermediate fence post will be suitable.
If the gate is being fitted between existing posts, check that both posts are secure, vertical and in good condition.
Allow for Hinges and Latches
The gate itself is usually slightly narrower than the full opening.
Space is needed for:
- Hinge clearance
- Latch clearance
- Expansion and movement
- The chosen gate furniture
- Posts or wall plates
- Adjustment during installation
The exact allowance depends on the hinge and latch type.
For example:
- Tee hinges usually fix to the face of the gate and post
- Hook-and-band hinges may require more space and adjustment
- Adjustable hinges may need additional clearance
- Wall-mounted hinges may use plates or hooks
- Latches and bolts need enough room to operate freely
Do not order the gate based only on the opening width without checking the fitting system.
Check the Ground Level
Check the surface beneath the gate and the area it will swing across.
Look for:
- Sloping ground
- Raised paving
- Steps
- Gravel
- Uneven soil
- Drain covers
- Kerbs
- Changes in level
- Areas where water collects
Use a spirit level or straight edge to check whether the ground is level.
A gate may fit correctly when closed but catch the ground as it opens.
Where the ground rises in the opening direction, you may need:
- Additional clearance
- A shorter gate
- A different opening direction
- Hinges that lift the gate as it opens
- Ground adjustment
Record the highest point across the full swing of the gate.
Decide the Hanging Direction
Decide which side the hinges will be fitted to and which way the gate will open.
Consider:
- Available space
- Ground slope
- Paths and access routes
- Buildings or walls
- Steps
- Parking areas
- Neighbouring property
- Wind direction
- The position of the latch
A gate should normally open without:
- Blocking a public path
- Hitting a wall or fence
- Catching the ground
- Restricting access
- Damaging nearby plants or structures
Stand on both sides of the opening and check the proposed movement before ordering.
Also record whether the gate should be viewed or described as left-hand or right-hand hung according to the supplier’s convention.
Measuring Between Walls or Existing Posts
Openings between walls or existing posts need extra care because they may not be square or vertical.
Measure:
- Width at top, middle and bottom
- Height at both sides
- Diagonal dimensions where useful
- Post or wall thickness
- Any offset between supports
- The condition of existing fixings
Where fixing to a wall, check:
- Wall material
- Wall condition
- Render thickness
- Whether suitable fixings can be used
- Whether a timber wall plate is required
- Whether the wall is straight and vertical
Where using existing posts, check for:
- Rot
- Cracks
- Movement
- Loose foundations
- Previous repairs
- Undersized posts
It is usually better to replace an unsuitable support than to fit a new gate to a weak one.
Common Measuring Mistakes
Avoid these common problems:
- Measuring only the old gate
- Taking only one width measurement
- Ignoring posts that lean
- Forgetting hinge and latch clearances
- Failing to allow for ground clearance
- Measuring the opening without checking the gate swing
- Using the widest measurement instead of the narrowest
- Assuming walls and posts are vertical
- Forgetting to include new gate posts
- Choosing the gate before deciding the hinge type
- Ignoring raised paving or sloping ground
- Failing to check whether the support post is strong enough
- Measuring in feet and ordering in millimetres without checking
- Not recording which side the hinges will be fitted to
Final Check Before Ordering
Before ordering the gate, confirm:
- Clear opening width
- Required gate width
- Required gate height
- Ground clearance
- Post size and material
- Hinge side
- Opening direction
- Hinge type
- Latch type
- Wall or post condition
- Ground slope
- Gate weight
- Wind exposure
- Matching fence style
- Required fixings
- Whether new posts are needed
Take photographs and prepare a simple sketch showing:
- Opening width
- Gate height
- Hinge side
- Latch side
- Opening direction
- Posts or walls
- Ground levels
- Nearby obstructions
Need Help Checking Your Measurements?
Bring your measurements, photographs and sketch into our Harlow store. Our team can help you choose a suitable gate, posts, hinges, latch and fixings.
Before You Start
- Check where the gate will be fitted
- Decide the gate type
- Confirm whether new posts are required
- Note walls, fences and obstructions
- Check the ground level
- Decide which way the gate should open
Need Help with Your Measurements?
Bring your measurements, photographs and a simple sketch into our Harlow store. Our team can help calculate the panels, posts, gravel boards and fixings required.