Here is a quick breakdown for adding and changing Normal Map intensity effect for adding damage look to walls or any surfaces in UE5.

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Is there a particular reason you're just putting the 1 value into the blue rather than just passing the blue channel back in?

When changing Normal Map intensity, you'll only want to change Red and Green channels but not Blue. That is what Component Mask is doing. Append +1 simply adds the Blue channel back in after adjustments. There are other setups you can do to be more clear, to do the same thing.

Great tip

There is a node called flatten normals. Might be more efficient way to do this.