Featheredge Fence Calculator – Boards, Posts and Rails
Enter the run and height and we'll work out the featheredge boards, posts, arris rails, gravel boards, postcrete and nails — with a cost estimate.
Featheredge Fence Calculator
You need
148boards
10m run at 1.8m high, including 10% waste
- 2.4m posts
- 5
- Arris rails
- 12
- Gravel boards
- 4
- Postcrete bags
- 10
How we worked this out
Your shopping list
148 × 100mm × 1.8m featheredge boards
134 needed plus 10% waste.
£237
5 × 2.4m treated fence posts
4 bays at 3m centres.
£90.00
12 × 3m arris rails
3 rails per bay for a 1.8m fence.
£72.00
4 × 3m gravel boards
Takes the ground contact so the featheredge stays dry.
£56.00
10 × 20kg bags of postcrete
2 bags per post.
£65.00
3 × 1kg boxes of 50mm galvanised ring shank nails
About 888 nails — two per board per rail.
£36.00
Featheredge fence quantities per metre of run
| Item | 100mm boards | 125mm boards | Notes |
|---|---|---|---|
| Boards per metre | 13.3 | 10 | 25mm overlap |
| Posts | 1 per 3m + 1 | 1 per 3m + 1 | Fence height + 600mm |
| Arris rails | 2 per bay up to 1.2m | 3 per bay above 1.2m | Length = post spacing |
| Gravel boards | 1 per bay | 1 per bay | 150mm or 300mm deep |
| Postcrete | 2 × 20kg per post | 2 × 20kg per post | 3 bags on corners and gates |
How this calculator works
Close board — or featheredge — fencing is built on site rather than dropped in as panels, so the quantities come from the run length rather than from a panel count. Each board overlaps the one before it, so the covering width is the board width minus the overlap. A 100mm board with the standard 25mm overlap covers just 75mm, which is why a 10m run needs 134 boards rather than 100.
Posts are worked out from the bays: run ÷ post spacing, rounded up, then one extra post to close the last bay. Arris rails follow the height — two per bay up to 1.2m and three above that, because a tall fence with two rails bows. Gravel boards are one per bay, and postcrete is two 20kg bags per post by default.
Worked example: a 10m run at 1.8m high
With 100mm boards at 25mm overlap: 10 ÷ 0.075 = 133.3, so 134 boards, or 148 with 10% waste for cuts, splits and the odd twisted board. At 3m post spacing you have four bays, so five 2.4m posts, twelve 3m arris rails (three per bay for a 1.8m fence), four gravel boards and ten 20kg bags of postcrete.
At typical merchant prices that is roughly £240 of boards, £90 of posts, £70 of rails, £55 of gravel boards and £65 of postcrete — around £520 in materials for a fence that a contractor would quote £1,100 to £1,400 to supply and fit.
Building it in the right order
Set a string line first, then dig the post holes 600mm deep with 100mm of compacted hardcore in the bottom for drainage. Set the two end posts, level and brace them, then run a line between them so the intermediate posts land dead straight. Let the postcrete go off for at least an hour before hanging rails.
Fit the gravel boards next, then the arris rails into the mortices, then start boarding from one end. Check plumb every fifth board — small errors in the overlap compound quickly, and it is much easier to steal 2mm across five boards than to cut a wedge at the end. Finish with a capping rail if you want the boards to shed water off their end grain.
Tips from the trade counter
- Buy pressure-treated everything. Featheredge, rails, posts and gravel boards should all be tanalised. Cut ends need end-grain preserver.
- Use ring shank galvanised nails. Smooth nails work loose as the boards move; stainless is better still near the coast.
- Nail through the thick edge only. Two nails per board per rail. Nailing through both thicknesses splits the boards as they shrink.
- Keep timber off the ground. Gravel boards should carry the ground contact, with the featheredge stopping 20mm above them.
- Talk to the neighbour first. Agree the boundary line and who owns the fence before you dig — it saves a great deal of grief later.
UK fence height rules
Under permitted development in England and Wales you can usually build up to 2m high at rear and side boundaries, and 1m where the boundary adjoins a road or a footpath used by vehicles. The height is measured from the higher ground level, and trellis on top counts towards it.
Listed buildings, conservation areas, new-build estates with covenants and properties where permitted development rights have been removed all have tighter rules. Always check with your local council before you build.
Frequently asked questions
How many featheredge boards do I need per metre?
With 100mm boards and a 25mm overlap each board covers 75mm, so you need about 13.3 boards per metre. With 125mm boards at 25mm overlap each covers 100mm, so 10 boards per metre.
How deep should fence posts go?
Roughly a quarter of the above-ground height, and at least 600mm. A 1.8m fence normally uses 2.4m posts set 600mm into the ground on a bed of hardcore, then concreted.
How many bags of postcrete per post?
Two 20kg bags per post is the usual allowance for a 1.8m fence. Exposed sites, corner posts and gate posts often take three.
Two rails or three?
Two arris rails up to 1.2m high, three above that. A 1.8m close board fence with only two rails will bow within a couple of winters.
How high can my fence be without planning permission?
In England and Wales, up to 2m at rear and side boundaries, and 1m where the boundary adjoins a road or footpath used by vehicles. Different rules apply to listed buildings and some estates — check with your local council.
Do I need gravel boards?
They are strongly recommended. A gravel board takes the ground contact and rot, and is far cheaper to replace than a whole run of boards. Concrete gravel boards last longest.
Which way do featheredge boards overlap?
Thick edge over thin edge, with each board overlapping the last by 25mm, working in one direction along the run. Fix with two galvanised nails per board per rail, through the thick edge only.