Garden Fence Panel & Post Calculator

Fence Installation Guide

What do I need to know about Fence Layout?

Number of panels = total run / panel width (round up). Number of posts = panels + 1 (one post each end plus one between each panel). Example: 25m run with 1.83m panels: panels = 25/1.83 = 13.7 → 14 panels. Posts = 15. Concrete per post: for a 6ft fence panel, posts should be approximately 2.4m (8ft) long — 600mm in the ground. A 200mm diameter × 600mm deep hole for each post. Postcrete per post: 1 × 20kg bag fills approximately 150-200mm diameter × 600mm hole. Allow 1.5-2 bags per post for a standard fence post hole, though larger or deeper holes for taller, more exposed fences will need more.

What should I know about Post Installation?

Depth of post: minimum 600mm for 6ft fence, 450mm for 5ft. Rule: 1/3 of post above ground + 1/3 in ground + 1/3 of panel height. Postcrete method: dig hole, put post in, pour dry Postcrete powder in, add water on top, level post, brace with temporary support. Sets in 10 minutes, full strength in 24 hours. Traditional concrete: slower but stronger for heavy-duty installations. Timber posts: use pressure-treated UC4 rated posts (rated for ground contact). Paint the end grain with preservative before positioning the post, since the cut end is the most vulnerable point for water to enter and cause rot.

What do I need to know about Gravel Boards?

Gravel boards are horizontal boards fitted at the bottom of the fence, between the posts, with the fence panels resting above them. Benefits: the bottom of fence panels is the most vulnerable to moisture damage. Gravel boards take the ground-level moisture and wood rot, and are replaced every 5-10 years rather than the whole panel. Most gravel boards are 150mm × 22mm (6 inches deep). Fit below the panel on brackets or in concrete post slots. For timber posts: attach with galvanised timber clips.

What should I know about Planning and Neighbour Considerations?

Planning permission: a fence up to 2m high generally does not require planning permission in most residential areas. Exception: adjacent to highways (limited to 1m without permission). Listed buildings, conservation areas, or existing conditions on your planning consent may restrict this. Party boundary: if the fence is on the boundary, the convention is that the post faces you and the smooth face of the panel faces the neighbour (but this is convention, not law). Ownership: Land Registry plans and title deeds sometimes indicate which boundary and fence a property is responsible for, though this isn't always marked clearly or consistently.