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# Window guardrail: when a low sill requires one

Made-to-order wrought-iron window guardrail, required when the sill and window frame together don't reach 0.90m — the French building regulation explained.
   [Get a quote](https://garde-corps-fer-forge.fr/en/quote/)
French building regulations

## The 0.90m rule

Unlike stair, balcony or terrace guardrails (governed by the NF P01-012 standard), whether a window guardrail is needed comes from a different rule set by French building regulations: if the combined height of the sill (the solid wall section below the opening) and the window frame already reaches 0.90m, no additional protection is required. Below that threshold, an added guardrail becomes necessary to secure the opening.

This 0.90m threshold answers a different question than the guardrail's own height once fitted: the first determines WHETHER protection is required, the second determines its height if it is — the two should not be confused.

> Detail on height rules by context (stairs, balcony, terrace) on our [standards and safety](https://garde-corps-fer-forge.fr/en/standards-and-safety/) page.

For comparison

## What's available off the shelf

Ready-to-fit window guardrail packs are found around 185 to 190 € in hardware stores — standardised products, designed for a common opening size, not for a particular configuration (non-standard reveal, unusual sill height, a style matching the rest of the facade).

> Market benchmark collected in 2026 (subject to change), not this workshop's own rates — see our [full pricing grid](https://garde-corps-fer-forge.fr/en/pricing/) .

Frequently asked questions

## What we're asked most often
        When is a window guardrail required?
When the combined height of the sill (the solid wall section below the opening) and the window frame is under 0.90m. Above that threshold, French building regulations do not require additional protection.
     What exactly is a "low sill"?
The sill is the solid wall section below a window opening. It's called "low" when, added to the window frame's height, it doesn't reach 0.90m — the threshold above which no protection is required.
     How tall does the guardrail itself need to be once fitted?
It follows the same dimensional principles as a balcony guardrail (1m as a reference), adjusted to the exact opening configuration and existing sill height — confirmed at the quote stage.
     What is the maximum baluster spacing for a window?
The same rule as for a staircase or balcony: 11cm maximum for vertical balusters over the full height.
     Does the guardrail fix inside or outside the window?
Both are possible depending on configuration (window reveal, facade) — confirmed at the quote stage based on your opening and the desired look.

Contact

## Describe your window

Opening width, current sill height — the workshop replies with a first estimate within 48h.