{"id":19919,"date":"2026-10-23T10:11:27","date_gmt":"2026-10-23T08:11:27","guid":{"rendered":"https:\/\/jansametal.com\/fire-resistance-of-metal-structures-r30-r60-r90\/"},"modified":"2026-10-23T13:42:57","modified_gmt":"2026-10-23T11:42:57","slug":"fire-resistance-of-metal-structures-r30-r60-r90","status":"publish","type":"post","link":"https:\/\/jansametal.com\/en\/fire-resistance-of-metal-structures-r30-r60-r90\/","title":{"rendered":"Fire Resistance in Metal Structures: R30, R60, and R90 Explained with Real-World Examples"},"content":{"rendered":"\n

How to Protect Steel Without Sacrificing Aesthetics or Overpaying<\/em><\/p>\n\n

\"\"<\/figure>\n\n

Before delving into regulations, it\u2019s worth dispelling two widespread misconceptions about steel and fire.<\/p>\n\n

The first is that Steel melts in a regular fire<\/strong>. That’s not the case: it melts at temperatures above 1,400 \u00b0C, and in the reference fire specified in the regulations, the air reaches about 1,000 \u00b0C after 90 minutes. What it does, however, is lose strength<\/strong> as it heats up. The second is that is the material most vulnerable to fire<\/strong>, for example, compared to concrete. This is only partly true: an unprotected profile heats up faster, but regulations require the same fire resistance as any structural material<\/strong>, and a properly designed and protected steel structure can do the same.<\/p>\n\n

That changes the question. It\u2019s no longer \u201cWhich material is safer?\u201d but \u201cHow many minutes must this structure hold up, and how can that be achieved?\u201d And the answer today is much easier to see than it was a few years ago: today\u2019s intumescent paints are thin, smooth, and can be finished in the project\u2019s chosen color<\/strong>, so the steel can remain exposed and be the building\u2019s focal point, without the thick, rough layers of the past.<\/p>\n\n

But the most important part happens before<\/em> painting. Effective protection starts with engineering: each part of the structure is calculated individually<\/strong> to determine what it needs, how much product it should receive, and how to comply with regulations without overspending.<\/p>\n\n

Let\u2019s start with the basics: what do R30, R60, and R90 mean; what temperatures does a structure actually reach during a fire; what do the regulations require; and how are these requirements met in practice?<\/p>\n\n

\"Metal<\/figure>\n\n

What do R30, R60, R90, and R120 mean?<\/strong><\/h2>\n\n

The regulations specify how long each structural element must withstand fire. This requirement is expressed as an “R”<\/strong> (for “r\u00e9sistance<\/em>,” or load-bearing capacity) followed by the number of minutes<\/strong>:<\/p>\n\n

Class<\/strong><\/td>What does<\/strong><\/td><\/tr>
R30<\/strong><\/td>The structure maintains its load-bearing capacity for 30 minutes<\/td><\/tr>
R60<\/strong><\/td>60 minutes<\/td><\/tr>
R90<\/strong><\/td>90 minutes<\/td><\/tr>
R120<\/strong><\/td>120 minutes<\/td><\/tr><\/tbody><\/table><\/figure>\n\n

Time is measured in a reference fire that is the same for everyone (the ISO 834 standardized curve), so that any solution is compared to the same standard.<\/p>\n\n

The UNE-EN 13501-2 standard uses three letters that should not be confused:<\/p>\n\n

Lyrics<\/strong><\/td>What is guaranteed<\/strong><\/td>Where it is required<\/strong><\/td><\/tr>
R<\/strong><\/td>The structure continues to bear its load<\/td>Columns, beams, floor slabs, trusses<\/td><\/tr>
E<\/strong><\/td>Flames and hot gases do not pass through to the other side<\/td>Elements that separate fire compartments<\/td><\/tr>
I<\/strong><\/td>The unexposed side does not overheat<\/td>Partition walls, doors, and floor slabs<\/td><\/tr><\/tbody><\/table><\/figure>\n\n

They are classified according to their function: a beam or column is R<\/strong>; a wall that separates sections is EI<\/strong>; a floor slab that supports a load and<\/em> separates sections is REI<\/strong>. Specifying \u201cEI 60\u201d for a beam is a common error in specifications and estimates: the correct designation is R 60<\/strong>.<\/p>\n\n

What temperatures does a structure face during a fire?<\/strong><\/h2>\n\n

Higher than many people imagine. In the standard test fire, the air around the structure exceeds 550 \u00b0C in about 5 minutes<\/strong>, reaching 842 \u00b0C at 30 minutes<\/strong>, 945 \u00b0C at 60 minutes<\/strong>, and 1,006 \u00b0C at 90 minutes<\/strong>.<\/p>\n\n

No structure is designed to withstand those temperatures on its own.<\/strong> That is why the code does not ask, \u201cCan it withstand the fire?\u201d but rather, \u201cHow many minutes can it withstand the fire before failing?\u201d<\/p>\n\n

And here\u2019s a very common misconception. It\u2019s true that steel doesn\u2019t melt in a building fire (its melting point is over 1,400 \u00b0C), but it doesn\u2019t need to melt to fail: it loses strength as it heats up, just like any other building material.<\/strong><\/p>\n\n

Steel Temperature<\/strong><\/td>Strength retained (approx.)<\/strong><\/td><\/tr>
Up to 400 \u00b0C<\/td>100%<\/td><\/tr>
500 \u00b0C<\/td>78%<\/td><\/tr>
600 \u00b0C<\/td>47%<\/td><\/tr>
700 \u00b0C<\/td>23%<\/td><\/tr>
800 \u00b0C<\/td>11%<\/td><\/tr><\/tbody><\/table><\/figure>\n\n

Reference values from Eurocode EN 1993-1-2.<\/em><\/p>\n\n

Since a structure bears less load during a fire than during normal use, the steel withstands the heat<\/strong> until it reaches its critical temperature<\/strong>, which is typically around 550 \u00b0C<\/strong> (this is a reference value; it is calculated for each individual component). An unprotected section can reach this temperature in a few minutes\u2014around 10 to 20, depending on its size.<\/p>\n\n

Fire protection does not make the steel stronger; it slows down its heating<\/strong> so that it does not reach that temperature before the required time has elapsed.<\/p>\n\n

\"ISO<\/figure>\n\n

Critical temperature of steel<\/p>\n\n

Each part is calculated individually<\/strong><\/h3>\n\n

Here’s what makes the difference: there is no “standard” protective thickness for an R60.<\/strong> Two beams in the same building, subject to the same load requirements, may require very different protective measures because two factors vary:<\/p>\n\n