I'm thinking of doing my own window replacement rather than pay for a FENSA registered installer and get if signed off by LABC but I'm aware that I may need to provide lintels if they don't already exist. The spans aren't great and I've read that you can use angle iron. How can I tell if a window already has these installed before removing the old window. Presumably they're fitted to the back of the brickwork course. Does anyone have a photo of one in situ? I'm replacing the original single glazed aluminium windows in a 70's bungalow.