Complete Guide

Fences & Picket Fencing

Everything you need to build a fence — from planning permission and neighbour notification through to post depth, timber grades and fixings.

Planning permissionTimber treatment classPost foundationsFrost heavePicket fencing

Planning & Regulations

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Check your local planning rules BEFORE erecting a fence. National guidelines are minimum requirements — your local authority may impose stricter limits on height and placement.

Boundary with neighbour

In most jurisdictions you may erect a fence on the boundary line. Notify your neighbour as a courtesy before work begins.

Boundary with road

Rules vary by location. Open, lightweight structures up to 1 m are generally permitted development. Solid fences and visibility splays: stricter controls apply.

Solid screen / wind break

Permitted development rules typically allow solid structures up to 2 m high. Higher or closer to a highway may require planning permission.

Boundary position

Confirm the legal boundary line before installation. A fence must not encroach on a neighbour's land. Check title deeds or land registry documents.

Fence Types

Type	Height	Use	Notes
Picket fence	900–1,200 mm	Garden, decorative boundary	48 mm pickets, 30–50 mm gaps
Close-board fence	1,200–1,800 mm	Privacy, garden boundary	Solid or 5 mm gap between boards
Slatted fence	900–1,800 mm	Contemporary, semi-transparent	20–50 mm gap between slats
Post and wire / rail fence	800–1,200 mm	Boundary marking, paddock	Cheapest, lowest maintenance
Ranch rail fence	800–1,000 mm	Decorative / rustic	No post digging required

Materials & Timber Grades

Timber treatment classes for outdoor use

All timber used outdoors must be treated to the correct use classⓘuse classEuropean timber use classes (EN 335) define the level of treatment required based on exposure to moisture and soil contact. Use class 4 covers ground contact; use class 3 covers above-ground exterior exposure.. Using the wrong treatment class is the most common cause of fence post rot.

Use Class 4 (UC4)

Ground and concrete contact. Mandatory for all posts set in the ground. Typically pressure-impregnated with preservative (green or brown tint).

Use Class 3b (UC3b)

Above ground, fully exposed with trapped moisture risk. Used for rails (stringers) and cladding boards. Withstands weather exposure.

Use Class 3a (UC3a)

Above ground, fully exposed but with rapid runoff. Minimum for fence boards — use UC3b for longer service life.

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Naturally durable species (oak, larch, western red cedar, Douglas fir) can be used untreated for above-ground applications but cost more. Softwoods such as pine and spruce must always be pressure-treated for outdoor use.

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Never cut pressure-treated timber without sealing all cut surfaces with end-grain preservative or end-grain primer. Cut faces are unprotected and will rot quickly. Fence boards must not rest on the ground — maintain at least 50–100 mm clearance.

Typical Dimensions

Component	Section	Treatment	Length
Post	75×75 or 100×100 mm	UC4	2.4–3.0 m (depending on fence height)
Rail (stringer)	47×100 mm	UC3b	Cut to panel width
Picket board	28×70 or 28×120 mm	UC3b	900–1,200 mm
Close-board / feather-edge	22×125 or 22×150 mm	UC3b	1,800 mm standard
Screws	Hot-dip galvanised 4.0×50 mm	—	Never use uncoated steel outdoors

Frost Depth & Post Setting Depth

The most common fencing mistake is posts set too shallow. Frost heaveⓘFrost heaveFrost expansion in the ground that pushes posts upward and out of position. The problem is worsened by water collecting around the post base and freezing. destroys fences whose posts are not set below the frost depth for the region.

Climate Zone	Typical Frost Depth	Recommended Post Depth
Mild coastal (e.g. southern UK, Atlantic coast)	0–300 mm	450–600 mm
Temperate inland (central Europe, northern UK)	300–600 mm	600–750 mm
Cold continental (northern/eastern Europe)	600–1,000 mm	800–1,000 mm
Subarctic (Scandinavia inland, Canada)	1,000–2,000 mm	1,100–1,500 mm

A simple rule of thumb: set posts to a minimum depth of 1/3 of the total post length, or to below local frost depth — whichever is greater.

Concrete Surround

Hole diameter: 3× post width (100 mm post → 300 mm hole)
Standard post: approx. 1.5 bags of 25 kg concrete mix. Corner/gate post: 2–2.5 bags
Place 150 mm of gravel or crushed stone in the base for drainage — never pour concrete against the bottom
Taper the concrete surface away from the post to shed water
Curing time: at least 24–48 hours before applying any load

Bolt-down / Spike Post Supports

Steel spike driven into ground; post slots into the bracket above soil
Advantage: post end does not contact the soil — no rot at the base
Typical drive depth: approx. 500–600 mm
Maximum recommended fence height: 1,200 mm using spike supports
Not suitable in loose soil or frost-susceptible ground

Step by Step

Measure the run and mark post positions. Always start and end with a post.

Post spacing: 2.0–2.4 m centres for picket fencing. Close-board (high wind load): max 2.0 m centres.
Run a taut string line between corner posts as a reference
Verify the fence does not cross the legal boundary — consult the title plan if in doubt
Notify your neighbour before installing a solid fence over 1,200 mm or where they may be affected

Depth is the most critical step — shallow posts are the leading cause of fence failure.

Use a post-hole borer (manual or hired petrol auger) — produces clean holes without disturbing the sides
Place 100 mm of gravel in the base for drainage
Set post, check plumb in both directions with a spirit level
Pour concrete and brace the post until set (use temporary wedges and support boards)
Crown the concrete slightly away from the post to direct water away

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Corner posts and end posts carry more load. Use a minimum 100×100 mm section and set them 100–150 mm deeper than intermediate posts.

Rails are the horizontal members that the cladding boards fix to.

Two rails for fences up to 1,500 mm high; three rails for taller fences
Top rail: 100–150 mm from the top. Bottom rail: 100–150 mm from the ground
Check rails are level with a spirit level
Fix with at least 2 hot-dip galvanised screws per joint, or use proprietary rail brackets

Start from a corner and work along the fence
Use a spacer block for consistent gap width between boards
Check vertical with a spirit level every 3rd or 4th board
Use a minimum 2 screws per board per rail (4.0×50 mm hot-dip galvanised)
Avoid screwing into end grain — poor holding strength and higher rot risk
Pointed picket tops: cut at 45° or use a jigsaw for a curved profile

Apply stain, oil or paint to all surfaces — including cut faces and end grain
End grain (tops of boards and posts) absorbs water most readily — apply two coats there
Pressure-treated timber can be painted after 6–12 months (allow to dry thoroughly)
Maintenance: re-apply a coat every 3–5 years depending on exposure
Inspect post bases annually — algae growth and soil packed against the post accelerate decay

Materials per Linear Metre

Common Mistakes

Calculate Fence Materials

Enter the fence length, height and style — get a full material list including posts, rails, boards, screws and concrete.

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Frequently asked questions

How deep should fence posts be set?

Set posts at least 1/3 of their total length in the ground, with a minimum of 24" depth. In frost-prone climates, posts should extend below the frost line (typically 36–48").

What wood is best for fence posts?

Use pressure-treated (PT) lumber rated for ground contact (UC4A or UC4B). Cedar and redwood can be used above-ground but PT is required for posts in the soil.

Do I need a permit to build a fence?

Many jurisdictions allow fences under 6 ft without a permit, but regulations vary. Always check local zoning ordinances and HOA rules and consider notifying neighbors before building.

References

→ TRADA — timber fencing design and durability guidance
→ AWC — wood construction standards including post foundations
→ Local planning authority — boundary fence height rules, permitted development rights and neighbour notification requirements

Post spacing, depth and concrete volumes are indicative. Actual requirements depend on fence height, soil conditions and local wind load. Last reviewed: May 2026