# Stainless Steel Fasteners for Facade Fixing

> Facade fasteners are the bolts, screws, anchors and clips that hold a facade to the building: a tiny fraction of its cost but the entire load path. Grade decides how long they last: A2/304 suits sheltered inland sites, while A4/316 resists the chloride pitting found in coastal, polluted urban and pool environments.

## What it is

The bolts, screws, anchors and clips that hold a facade to the building. They
are a tiny fraction of the cost and the **entire load path**.

## Grade selection

| Grade | Where it belongs |
| --- | --- |
| **A2 / 304** | Inland, low pollution, sheltered |
| **A4 / 316** | Coastal, polluted urban, pool environments |
| Duplex | Severe exposure, high load |
| Carbon steel | **Never** in contact with aluminium or externally exposed |

## What the specification must state

- **Grade** in explicit terms, A2 or A4 / 304 or 316
- **Property class** for strength, per ASTM A193 or the IS equivalent
- **Isolation** requirements where dissimilar metals meet
- **Edge distance** and embedment for anchors
- **Torque** values, since over-tightening is as damaging as under-tightening
- **Pull-out test** requirement on the actual substrate

## Why this is not a minor item

A facade panel is held by its fixings. When a fastener corrodes, loses preload
or pulls out, the panel is what falls — and panels fall from height onto public
areas. Every facade failure investigation looks at the fixings first.

That is why the fixing schedule deserves the same attention as the panel
specification, and why substitution at site level — when the specified fastener
is not on the trolley — is a genuinely serious act rather than a practical
shortcut.

## Where projects go wrong

- **304 used in coastal exposure**, pitting within a few seasons.
- **Carbon steel substituted on site** because it was available.
- **No isolation** between dissimilar metals in aggressive exposure.
- **No pull-out testing** on the actual substrate, especially into old or
  variable concrete.
- **Over-torqued fixings** crushing gaskets, distorting panels or stripping
  threads.

## Standards referenced

Stainless fastener material under **IS 6603**. Bolting property classes under
**ASTM A193**. Wind loading that the fixings must resist under
**IS 875 (Part 3)**.

## Frequently asked questions

### When must 316 be used instead of 304?

Anywhere chlorides are present: coastal sites, swimming pool environments, and heavily polluted urban atmospheres. The molybdenum in 316 resists chloride pitting; 304 does not, and in those environments it pits and streaks within a few seasons. Since the fastener is often a tiny fraction of the panel cost and the entire fixing depends on it, 316 is cheap insurance wherever there is doubt.

### What is tea staining and is it structural?

Tea staining is a brown surface discolouration on stainless steel, most common in coastal and marine air. It is a cosmetic surface effect rather than structural corrosion, so the fastener retains its strength, but on a prestige elevation it looks like rust and clients treat it as a defect. A higher grade, a smoother surface finish and regular washing all reduce it.

### Can stainless fasteners be used directly into aluminium?

Generally yes, because the galvanic difference between stainless and aluminium is moderate, and it is common practice on facades. In severe or chloride-rich exposure, isolation washers or sleeves should be used to break the contact. The combination to avoid entirely is carbon steel against aluminium, which corrodes quickly and is still used on site when the right fixings run out.

## Sources

- [IS 6603](https://standards.bis.gov.in/website/published-standards/department-wise) — Stainless steel bars and wires for fasteners
- [ASTM A193](https://www.astm.org/products-services/standards-and-publications.html) — Alloy steel and stainless steel bolting
- [IS 875 (Part 3)](https://standards.bis.gov.in/website/published-standards/department-wise) — Wind loads on buildings

---

Source: https://hagerstone.com/materials/stainless-steel-fasteners-facade