04 Oct 2026
8" Fence Post in black: height, groove sizes and posts per run
This guide is about
8" Fence Post - Black (1 Pack / 2pcs)
A fence is only as straight as the posts holding it. The 8" Fence Post - Black (1 Pack / 2pcs) is the taller of the two composite posts in the fencing range, listed at 10 x 10 x 240cm, and it is the one to look at when a boundary needs height or the ground falls away along the run.
What the listing states
- 10 x 10 x 240cm per post.
- Two posts per pack.
- A three-way post, grooved to take 2cm thick fence panels.
- Grooves 20mm wide and 18mm deep.
- Composite, black finish, described as UV-resistant and as resisting rot and splitting.
- Described as designed to be buried 2" underground for strength and stability.
- Supplier code AWS-ID16086218342782.
Two of those figures are worth reading twice. The grooves are 18mm deep, so a short length of every board sits hidden inside the post, which means post centres are not simply the board length. And the inch mark in the name is a trade label: the dimension to work to is the 240cm the listing gives, because the listing does not explain the name.
How many posts a run takes
The composite boards in this range are 180cm long, so a bay works out at roughly 180cm across once the groove depth at each end is allowed for. Posts sit between bays, so a run always needs one more post than it has bays.
| Run length | Bays at 180cm | Posts | Packs of 2 |
|---|---|---|---|
| 1.8m | 1 | 2 | 1 |
| 3.6m | 2 | 3 | 2 |
| 5.4m | 3 | 4 | 2 |
| 7.2m | 4 | 5 | 3 |
| 9.0m | 5 | 6 | 3 |
Always round up, and expect a spare: posts come two to a pack, so an odd number leaves one over. Set the positions out with a line and pegs before you order, allowing for the 18mm the groove swallows at each end of a board.
Height, and how the post is fixed
Twelve boards at 15cm each stack to 180cm, which is the full height of a bay in this range. A 240cm post therefore stands 60cm clear of that stack before any of it goes into the ground, which leaves room either for a taller boundary or for setting the post down into soil. The listing gives the setting depth as 2" and says nothing more about ground conditions, so ask the shop what it advises for the ground you are digging into.
Where the surface is concrete or tarmac there is nothing to dig. The Fence Post Fitting Kit - Black is listed for slabs, tarmac and similar floors and includes a post hat, base cover, bracket and stainless steel bolts. One thing to settle before ordering: the kit's own listing names the 8 x 8cm post pack, so confirm with the shop that the bracket suits a 10 x 10cm post.
What it works with
The post is grooved for 2cm boards, which is the thickness of the composite fencing here. Fencing 86A - Oak 03 is listed at 15 x 180 x 2cm per fitted board, six to a pack and two packs per bay. If a lower fence or a shorter run suits the garden better, the 6" Fence Post - Black (1 Pack / 4pcs) is the same idea at 8 x 8 x 190cm, four posts to a pack. Both post listings are black only, so if the boards are one of the wood-named or grey finishes the posts will read as a contrast rather than a match.
Before you order
- Measure the run, mark the post positions, and count one more post than bays.
- Decide between digging and bolting down, and ask which fixing suits a 10 x 10cm section.
- Check the board finish against a black post while you are in the shop.
- Delivery is free within 50 miles of the Glasgow store and £50 beyond.
If the run is long or the boundary needs the extra height, the 8" Fence Post - Black (1 Pack / 2pcs) is the one to price up, and the shop can check the groove and bracket combination against the boards you have chosen before anything is ordered.