An old fuse box is not illegal, and age on its own is not a reason to change one. What matters is what it does and does not protect against. If yours has rewireable fuses with wire in them, or a row of plug-in cartridge fuses and no test button anywhere on it, then it has no fast-acting shock protection at all. That is the main reason to replace one.
The other triggers are practical. You are adding an electric shower, a car charger or an extension and there is no spare way. Circuits keep tripping and the board makes it impossible to tell why. Your EICR flagged the board. Or it is corroded, warm to the touch or smells hot, in which case it should be looked at straight away rather than added to a list.
Rewireable fuses
The clearest reason. No fast shock protection, and the fuse rating depends on whoever last rewired it.
No spare capacity
Adding a shower, a charger or an extension with a full board means replacing it is part of the job anyway.
Heat, smell or corrosion
Any of those means stop and get it looked at now, not at the weekend.
Your questions, answered
How much does a new fuse box cost?
A standard replacement around King's Lynn and West Norfolk is usually £450 to £800 depending on the number of circuits and what we find behind the old board. Fixed price before we start.
Is my old fuse box illegal?
No. Old boards are not illegal and you cannot be forced to change one in your own home. It will be noted on any EICR though, and if you let the property that matters.
Will a new board stop things tripping?
Not if a circuit has an actual fault. A modern board is more sensitive, so it can trip more at first. We test the circuits before fitting so we find any fault beforehand.
How long does it take?
Usually one day, with the power off for a few hours in the middle. Everything is tested before we leave and you get the results in writing.
Ready for electrics done properly?
Free fixed quotes across King's Lynn and Norfolk. Careful work, an immaculate finish and a price that doesn't move.