Holding Down Bolts — M16, M20 & M24 Sets
Our holding down bolt sets provide a reliable way to anchor steel columns, stanchions and structural elements to concrete foundations. Each set is supplied complete — bolt, nut, square plate washer and tapered waxed cone — in M16, M20 and M24 as standard.
The bolts are manufactured to British Standard and supplied in a self-colour finish, with hot-dip galvanising available as an option on commonly stocked sizes. We also make up complete holding down bolt clusters (boltboxes) in our Burnley workshop, set out on plywood templates to the exact dimensions on your foundation drawings — ideal for steel fabricators, groundworks and civil engineering contractors who need the bolts positioned accurately on site.
Browse the sets below, or request a quote with your sizes, quantities or setting-out drawings.
Holding Down Bolt Set (M16)
Holding Down Bolt Set (M20)
Holding Down Bolt Set (M24)
What’s included in a holding down bolt set
Each holding down bolt set is supplied complete and ready to cast in:
- Holding down bolt – manufactured to British Standard, supplied in a self-colour finish
- Hex nut
- Square plate washer sized to the bolt
- Tapered waxed cone to form the void for adjustment and grouting
Sizes and finish
| Size | Standard finish | Typical use |
|---|---|---|
| M16 | Self colour | Lighter portal frames, mezzanines, smaller stanchions |
| M20 | Self colour | Standard steel portal frames and industrial units |
| M24 | Self colour | Heavier structures, distribution centres, stanchion bases |
Galvanised finish: hot-dip galvanising is available as an option on the most commonly stocked sizes for added corrosion resistance. Galvanised orders carry a small premium and a longer lead time, so please order early. Ask us which sizes are available galvanised.
Boltboxes & clusters made up to your drawings
As well as individual sets, we make up complete holding down bolt clusters (boltboxes) in our Burnley workshop. Your bolts are fixed into a plywood template at the exact centres and projection shown on your foundation drawings, so the cluster drops straight into the shutter and casts in true – saving time and avoiding setting-out errors on site. Send us your setting-out drawing for a quote.
Applications
Holding down bolts (also called HD bolts, hold down bolts or foundation bolts) anchor structural steelwork to concrete. BoltBox supplies them for steel portal-frame buildings, industrial and warehouse structures, distribution centres, and stanchion bases for overhead signs, floodlights and similar structures.
Why choose BoltBox
- Boltboxes and clusters made up in-house in Burnley to your drawings
- Bolts manufactured to British Standard
- Self colour as standard, with galvanising available on common sizes
- Complete sets supplied with nut, square plate washer and tapered cone
- Fast quotes and dispatch to site to suit your programme
Request a quote → or call 07929 142325
Holding down bolts – FAQs
What are holding down bolts used for?
Holding down bolts secure structural steel columns and stanchions to concrete foundations. They are cast into the foundation so the steel can be bolted down accurately once the concrete has cured.
What is a holding down bolt cluster (boltbox)?
A boltbox, or cluster, is a group of holding down bolts fixed into a template at the correct spacing and projection so they can be cast into the foundation accurately. We make these up in our Burnley workshop from your foundation drawings.
Are your holding down bolts galvanised?
Bolts are supplied in a self-colour finish as standard. Hot-dip galvanising is available as an option on the most commonly stocked sizes for added corrosion resistance; galvanised orders carry a small premium and a longer lead time.
What sizes of holding down bolts do you supply?
M16, M20 and M24 sets are available as standard. We also make up complete clusters (boltboxes) to the sizes and centres on your drawings.
How are holding down bolts set into concrete?
They are positioned using a template before the pour, with a tapered waxed cone forming a void around the thread to allow final adjustment and grouting. The cone is supplied with every set.