I'm replacing two small windows in the 1st floor bathroom with one large PVC window 1890mm long. The old timber lintel spans both existing windows and is 2680mm long by 155mm high by 75mm wide and the 4x2 wall plate sits on top. I will be removing the masonry pillar between the two existing windows, but the water tank in the loft is located on ceiling joists which bear on the centre of the timber lintel. The pitched roof above is of clay pantiles, so also quite heavy. I have now just found that one end of the timber lintel is completely rotten and the whole lintel now needs replacing. The wall plate is also rotten in the same area but the roof truss timbers are OK. Phew! What sort of lintel should I use to replace the timber one with? Any other advice will also be very welcome.