I have a fireplace that was blocked up with hardboard.
Looking behind the board, i have a bruick arch, but also a very thin (10mm thickness) wooden beam right below the arch. This beam is keyed into the brick at either end - see attached image
This beam seems far too flimsy to be a lintel - the load is surely taken by the arch, but the fact it is keyed in seems odd. Might it have been put in to support the arch during construction, and simply never removed?
I don't need to remove it either, but would like to understand why it is there...
Sorry I thought you meant a curved arch. You are sure it is timber and not iron or steel? I looks as though it's an old building, if so then it was the practice in days gone by to use a thin piece of iron plate to support a brick arch such as this. If it is timber then I cant see how it would survive the fires so close.