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Why Are The Metal Tabs Protruding From My Poured Concrete Foundation Walls?

Many homeowners notice and complain about little tabs of metal sticking out of their foundations; often, these are rusty, and apart from the eyesore, they can hurt people unaware of the protuberance. These pieces of metal can also let water into your basement! But what are they?

In the building world, these metal tabs are called “form ties.” As the name suggests, many builders use them to keep the inner and outer concrete forms in position, and most are designed to be snapped off after the concrete hardens. However, sometimes these ties aren’t properly removed, and you’ll notice them sticking out and making the surrounding concrete rusty. What can you do with any protruding metal tabs?

What Are The Metal Tabs?

fiorino-concretewall-whataremetaltabsForm ties are used in concrete foundations during the construction phase. These pieces of metal hold two opposing sides of concrete forms together when the contractors pour the foundation at the proper distance to create the right concrete thickness. Once the concrete dries, the full tie cannot be removed, but a modern type called the snap tie has a weaker cross-section so that the worker can break the tie off on the inside of the foundation. 

When the snap tie properly breaks off, the metal should sit flush with or below the surface of the concrete; the hole can then be patched over with cement. Form ties still leave their mark on the concrete: after it’s broken off, a snap tie leaves a small dimple on the inside walls of the foundation. Workers should remove any form ties as early as possible after removing the concrete form. If the basement isn’t finished, or if they were not broken off and patched properly, the bars can protrude from the concrete. If it creates a weakness in the foundation, outside water can rust the ties, stain the wall, and even cause spalling and pitting in the concrete.


Removing The Metal Tabs From Your Poured Concrete Foundation

Even if the snap ties are removed, they can leave your concrete foundation vulnerable to water damage. The damage becomes evident on the inside in the form of a small stain roughly the size of a Loonie, but you might notice a water line that leaks down to the floor. If you see metal tabs coming out of your home’s foundation, or there are degradations around the depressions in the concrete that signal the presence of form ties, have them patched over or repaired ASAP.

Sometimes, it’s necessary to seal off the metal form ties by getting right into the concrete. Contractors would drill next to the tie, put ports in, and inject the ports with closed polymer resin. This resin material stops water and air from coming in, preventing leaks that can degrade your concrete and lead to flooding. Even if leaks aren’t coming out through the holes of the form ties, you should have them covered as preventative maintenance.

If you see the metal tab of a form tie coming out of your foundation, you can try and remove them by hitting them with a hammer bending them back and forth with a wrench. Because they’re hardened steel, they should snap off, but if it’s not coming off, call a concrete professional to have them removed without doing damage to your foundation.

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