How much crash barrier do I need?
Work in beams, not metres. Here is how to turn a run length into beams, posts, bolts and terminals without ordering twice.
The single biggest cause of a second delivery on a barrier job is the beam length. A beam measures 3504mm, but 304mm of that disappears into the overlap at the post. Order on 3504 and you will be short.
Beams
Divide the run by 3.2m and round up. A 20m run is 20 / 3.2 = 6.25, so seven beams. A 50m run is 15.6, so sixteen.
Beams by run length
| Run | Beams | Posts |
|---|---|---|
| 10m | 4 | 5 |
| 20m | 7 | 8 |
| 30m | 10 | 11 |
| 50m | 16 | 17 |
| 100m | 32 | 33 |
Posts
One post per beam, plus one to finish the run. Seven beams means eight posts. Then pick the profile — Z post for car parks and yards, H post where the barrier is protecting racking, plant or a structural line — and the length, remembering the figures quoted are overall lengths of steel, not heights above ground.
Pick a post
Bolts
Two different M16s, and this is the other reorder we see constantly.
- Post bolt, M16 x 50mm — beam to post. One at every beam-to-post connection.
- Lap bolt, M16 x 35mm — beam to beam at each overlap, and corners and terminals onto the run.
Count them off the layout rather than guessing a ratio, because corners and terminals change the count. Then add spares. A handful of M16 bolts is the cheapest insurance on the job, and running out stops the install.
Both bolts
Corners and ends
One corner section per change of direction — internal for the inside face of an angle, external to wrap the outside. Then two terminals per run, chosen by who is on foot: pedestrian ends where the run finishes beside a walkway or door, fish tail ends everywhere else.
Corners and terminals
Bolt-down runs
If the posts are base plated rather than dug in, add the anchor fixings — they are a separate item from the barrier bolts, sized to the post and the slab. Order those to the post count, plus spares, and check the concrete before the day.
Frequently asked questions
- How many crash barrier beams do I need for a 20m run?
Seven. Beams are 3.2m effective once overlapped, so 20 / 3.2 = 6.25, rounded up. You would need eight posts with them.
- How many bolts per crash barrier beam?
It depends on the layout rather than a fixed ratio — a post bolt at every beam-to-post connection, plus lap bolts at every beam overlap, corner and terminal joint. Count them off the drawing and add spares.
- Do I need a post at each end of a crash barrier run?
Yes. It is one post per beam plus one more to finish, so a seven beam run takes eight posts.