Can I fit composite fencing between concrete posts?

Can I fit composite fence boards between my existing concrete posts?

Yes, if the posts are sound, upright and the right distance apart. The Nova concrete post adaptor is a U channel that gives the board ends a slot to sit in on each post, so the old panels come out and the posts stay. The digging is most of the labour on a new fence, which is why people ask.

The adaptor suits posts that are sound and upright. Posts set at regular spacings suit it best, because the board length is fixed. Measure the clear gap between post faces for every bay.

What does the U channel adaptor do, and what size is it?

It is a composite channel, 1,830mm long and 40mm, and it can be trimmed to adjust the length. The adaptor suits fence panels 18 to 21mm thick, and the Nova boards are 19mm thick, 152mm high and 1,800mm long. The boards are secured within the channel using some silicone, and the adaptor leaves no screws on show.

Posts differ in profile and in how the slot is cut, so check your post against the product page, or bring a measurement or a photo to the counter. The fitting steps for the aluminium-post version are in the composite fencing guide, and the order of boards is the same.

Concrete posts with adaptors, or new aluminium posts?

Two ways to post a Nova composite fence

Item	Existing concrete posts and U channel	New Nova aluminium posts
What you buy	U channel adaptors (1,830 x 40mm) and boards	Posts, 75 x 75mm, in 1.9m or 2.4m, and boards
Digging	The posts stay where they are	2.4m post is buried for a 1.8m fence; 1.9m post fixes to a base
Post fittings	Silicone in the channel	Post caps and, for 1.9m, a base plate, included
Posts must be	Sound, upright, close enough for the boards	Set to a string line at the spacing you choose
Boards	1,800 x 152 x 19mm, black or anthracite	The same boards
Ends of a run	Starting and finishing sections	Starting and finishing sections

If the existing posts are good, the adaptor saves the digging and the concrete. If you have to replace more than a few, new posts are simpler than propping and levelling old ones. Both routes use the Nova composite fencing panel, and the Nova Composite Fencing package is configured by post type, colour and finish if you want it picked together.

How far apart should the posts be?

The fitting guide’s rule is a clear gap about 60mm less than the board length. For the 1,800mm Nova board that is about 1.74m between post faces, leaving around 30mm of board in each channel. Old timber panels on 1.83m centres are close to that, though the exact figure depends on the width of your post. Take any shortfall on the last bay and cut one board down. Keep the remaining bays to the calculated gap.

How many boards make the panel height?

Divide the height by the 152mm board height. The adaptor can be trimmed, so a lower fence is possible. The 2.4m aluminium post is sold for a 1.8m finished fence, so the figures here work to 1.8m.

Boards for a bay, from the 152mm board height

Fence height	Boards per bay
0.6m	4
0.9m	6
1.2m	8
1.5m	10
1.8m	11 to 12, as the fitting guide says

These come from the board height alone, so build one complete bay, count the boards it took, and then order the rest. Each board is 1.8m long, so one board is one bay wide. Check with your council before putting up a tall fence.

How many adaptor lengths do I need?

Count one length for every post face a bay butts against. A bay between two posts has two faces, so two lengths. An intermediate post serves two bays and so carries a channel on each side. At the end of a run against a wall or a pier, use a starting or finishing section instead of one channel.

For example, three bays at 1.8m high between four concrete posts needs 36 boards (3 x 12), 38 with 5% added, and six lengths of adaptor (3 bays x 2). If one end meets a house wall, swap one adaptor for a section and keep five. Boards, adaptors and sections are all in Nova fencing items.

What are the starting and finishing sections for?

They close a run at a wall or pier in place of a post, so the board ends slot in and the cut edges are hidden. The Nova starting and finishing sections are aluminium, 1,800 x 20 x 55mm, and we recommend them for every Nova fence. Fix the section plumb to the wall before any boards go in, because the boards feed into it. Where a run meets a building at an angle or steps down a slope, measure it and ring us, and we will work out the parts with you.

Which silicone secures the boards?

The boards are secured with silicone. The catalogue has Silirub LM in black and anthracite grey, which are the board colours, and Soudal Trade Multi Purpose Silicone in clear, white or brown. Check the sealant page against the surface, and ask us which suits your board colour. The other options are in silicones.

Where can I get the parts in Liverpool?

Collect free from the Liverpool showroom at Unit 7, The Boxworks, Heysham Road, L30 6UR, Monday to Friday 7:30am to 4:30pm and Saturday 7:30am to 1pm. Delivery is priced by postcode and shown on each product page and at checkout. Bring the post spacings and heights for each bay, and we will work the quantities with you. For posts to bury, the Nova aluminium post is in the same range.