Kick plates are added to fire doors constantly, usually by a maintenance team responding to damage, and they are one of the most frequent causes of an otherwise sound door falling outside its certification. The plate itself is rarely the problem. The fixing method and the size are.
Why the fixing matters
A doorset was tested as a sealed assembly. Screws driven through the leaf create a path through the core and can carry heat into it, and a plate fixed on both faces with through bolts creates a continuous metal path from the fire side to the escape side. Certification schemes therefore state how a plate may be attached: usually adhesive of a specified type, or short screws that do not penetrate beyond a stated depth, and often only to one face.
Size limits
Most certifications limit the height of a plate and require it to stop short of the edges of the leaf so that the intumescent seals and the perimeter are not covered or interfered with. A plate that runs to the full width can trap the seal or interfere with the closing gap. The limit is in the manufacturer's instructions, and there is no universal figure.
Intumescent backed plates
Plates supplied with an intumescent backing are made for this purpose and are the straightforward answer where a certification permits them. They are more expensive than a plain plate from a general hardware supplier, and the difference in price is the evidence that the door remains as tested.
What to do about the underlying problem
Kick plates are fitted because doors are being kicked, usually by people carrying things through a door that closes on them. Where that is happening, a hold open device released by the alarm often solves the cause rather than the symptom, and costs less over time than repeated leaf replacement.
Questions people ask about fire door kick plates
Can a kick plate be screwed on?
Only if the doorset's certification allows screws, and then at the depth and pattern it states. Through fixings are generally not permitted.
Does a kick plate need to be on both sides?
Only if the certification permits plates on both faces. Many allow one face only, because a plate on each side creates a heat path through the leaf.
Does fitting one void the certification?
Fitting one outside the manufacturer's instructions does. Fitting a permitted plate by a permitted method does not, and the instructions are the document that decides.