Is your property protected against invisible damage to load-bearing iron profiles?

Do you know the condition of your property's hidden structures? If you own or are responsible for maintaining older properties, you should be aware that it is not only balconies that are at risk of collapse.

This also applies to other structures designed with so-called cantilever irons. In addition to balconies, cantilever irons are also used in bay windows and some deck structures, such as filler-joist floors, jack arch floors or floors with iron beam systems, as well as iron lintels above windows and doors. And it is precisely corrosion in cantilever irons that has caused many of the collapsed balconies.

So what can you do to avoid the structure collapsing in the worst case? In this article, you will get advice on how to inspect and repair corrosion damage in existing structures with cantilever irons.

What is the problem with cantilever irons in older properties?

Cantilever irons are the steel structure that connects the balcony, bay window or deck to the property's facade, which is most often an external brick wall.

The problem arises when the cantilever iron starts to rust. You cannot always see this with the naked eye. And if you can see it, you can be sure that the problem is already serious. The rust product can occupy up to 10 times as much as the iron profile itself. So when the wall cracks, it may be because the rust is pressing against it, and you may have a serious problem.

Voids and moisture are the main culprits

Rust starts to form if the iron profiles are not properly protected by the mortar and when moisture gets in. The moisture problem can arise naturally due to rain penetrating the masonry. But the moisture can also come from inside if there are defective water pipes or drains in the property, or because condensation forms on the steel structure.

The condensation comes from the cold bridge that occurs when the cold iron profile from the outside meets the warm air inside the building. The mortar is often a masonry mortar that does not provide good protection against corrosion, and there are often voids because the masonry has not been laid correctly around the iron profile; there is simply a lack of mortar.

The older the structure, the greater the risk of corrosion in the load-bearing structure. This shortens the service life of the structure.

How to inspect the condition of the load-bearing steel structures

There is a limit to what non-destructive testing can be carried out to assess the condition of the cantilever irons inside the wall. As a starting point, you can measure moisture in the wall and look for cracks in the external wall.

Therefore, our best advice is to screen the steel structures by physically opening up access to them, so that they are exposed. This is typically done by removing some of the bricks in the facade, so that you can see the current condition of the cantilever iron.

It is also important to look at the bearing plates on which the iron profiles rest. We have seen several cases where much of these plates were severely corroded and therefore were no longer suitable for distributing the load to the masonry.

There are no rules for how many places you need to open up the structure, but it is important to choose places that are representative of the rest of the property. An experienced inspector knows where the critical points are, how deep you need to go to get an accurate picture of the condition, and how to open the structure without causing it to collapse.

How you repair the damage depends on the extent

Once you know the extent of the damage, you need to determine how best to repair it. If the cantilever iron is badly affected by corrosion, you need either to replace it or reinforce it. You must assess whether it is so deteriorated that it can no longer fulfil its function and whether the load-bearing capacity is therefore threatened. This can leave you with a dangerous structure that, in the worst case, may collapse.

If the steel structure is not badly affected, it may only be necessary to protect the iron profile with a zinc-containing paint. You can also consider whether the best solution is to use cathodic protection. Here, you apply a weak current to the cantilever iron, which prevents corrosion from occurring in future. In this way, you significantly extend the service life of your property.

Alternatively, you can choose to monitor the development of the rust if everything looks reasonably sound, and then carry out a new condition assessment in, for example, five years.

If there is moisture in the masonry, you must of course also find the source of this and ensure that it is stopped.

Contact us if you need to have your property inspected or have questions about your load-bearing structures.