Toughened, Laminated, Float or Double Glazed: Which Glass Goes Where

Most people only think about glass types when something breaks. This is a plain guide to the four you will actually be offered, how each behaves when it fails, and where the standards require which.

Float glass

Ordinary glass with no safety treatment. Cheapest, and can be cut to size on site, which makes it the fastest to replace.

How it breaks: into large, sharp shards. This is the one that causes serious injuries, and it is why the standards changed.

Where it belongs: positions where nobody can walk into it and AS1288 does not require safety glazing. Plenty of older homes still have it in places it would no longer be permitted.

Toughened (tempered) glass

Heat treated so the surface is in compression and the core in tension. Much stronger than float against flat pressure.

How it breaks: all at once, into small blunt granules. Safer fragments, but you lose the entire pane rather than getting a crack. A concentrated impact on an edge or a weak point releases the whole sheet.

The catch: it cannot be cut, drilled or modified after manufacture. Every panel is made to final size, which means roughly five days of processing and no on-site adjustment.

The other catch: toughened can fail spontaneously, years later, with nothing touching it. The usual cause is nickel sulphide inclusion, a microscopic particle trapped during manufacture that eventually expands and releases the stored tension. We attend these regularly, and it is never something the homeowner did.

Laminated glass

Two sheets bonded to an interlayer. Our most common replacement, and usually what we recommend.

How it breaks: it cracks and stays in place. The interlayer holds every fragment, so a break is a damaged panel rather than an open hole.

Why that matters: nothing falls into a doorway, a walkway or a child's bedroom. It also makes forced entry considerably harder, and it is not subject to spontaneous failure.

We have seen a shopping trolley hit a laminated shopfront at shopper height and not one fragment reach the walkway. That is the argument in one sentence.

Double glazed units (IGUs)

Two panes with a sealed cavity between them, manufactured as a single sealed assembly for thermal and acoustic performance.

How they fail: either a pane breaks, or the seal fails. Watch for condensation forming between the panes. That fog is inside a sealed cavity, cannot be cleaned, and means the unit has lost its insulating value even if the glass looks fine.

The constraint: a broken pane cannot be replaced on its own. The whole unit is replaced, custom made to the frame, which is why it is never a same-day job.

Where safety glass is required

Under AS1288, human-impact areas need compliant safety glass, which in practice means laminated or toughened. That covers doors and side panels, low-level windows, glass in and around wet areas like bathrooms and showers, and anywhere someone could reasonably walk into it.

Safety glazing also has to be permanently marked, so an inspector, insurer or future owner can verify it. Glass without those markings is effectively unverifiable, however good it is.

What we would put in your house

In most residential positions, laminated. It looks identical to what came out, it holds together when broken, and it turns the next accident into a booked repair rather than an emergency callout.

Where a position genuinely does not require safety glass, we will fit like-for-like and charge you less. The recommendation follows the position, not the invoice.

See glass replacement services for what we supply and install, shower screens for bathroom glazing, or emergency glass repairs if something is broken right now.