This would not be capital in my book. It’s repair. It’s akin to servicing or replacing the boiler would be my view.
And it will have to be done every few years.
To me capital is adding an extension or converting an attic. Something substantial.
One time new double glazing was considered capital. Now it’s not. As an example of how things changed. There was also the thing about garage forecourts, about the canopy overhead. One of the accountants or revenue guys on here might remember that from back in the day.