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I have taken down the ceiling in a small kitchen in a cottage bungalow with a view to opening up the void to create a feeling of space and to put a roof window in. The kitchen roof can best be descried as a ‘lean too affair’. The joists supporting the roof are 8 feet long by 2 ½ x 2 ¼ and there are 10 of them at 16 inch intervals. They angle up at about 30 degrees. They are supported by one long cross beam which sits on two other beams underneath running at right angles. The tiles are very new and are man made. My first impression is the joists are not thick enough and were obviously put in when the house was built (1895) . I would have preferred them to be 4 x 2. I am wondering if I put in another 8 joists ( 4 x 2) in between the others would this allow me to take out the cross beam and the other two beams sitting underneath?

merlin1244,
As a general guide 100x50 rafters at 400 centres should be OK over a clear span of 2.4m. If you are fitting a roof window you should double up the rafters either side of the window.
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