Hi,
I am hoping to be able to use existing loft joists in a loft conversion without putting in a whole new load of joists. The middle 3 feet of the room is supported by staircase walls below, then if I put steels 6 feet further out on both sides (behind or below new roof supporting dwarf walls) and use hangers off them to support the existing joists (bit of damage to ceiling below but that needs underboarding anyway) that would give me a room 15 feet wide and lose no head height/ save on new/twinning joists.
The (Trada?) domestic span table I have goes as small as 97mm x 47mm joists at 400mm centres - the span given is 1.92 metres for C16. Mine are 85mm x 47mm at 360mm centres. (Timber is up to 150 years old, so am assuming it as equivalent to C16 not C22)
Does anyone know if there is a table for 85mm joists? Or a bit of software to do the calculation? Or is 85mm just too thin? It would save a fair bit on timber and work doing it my way, but most of all save valuable headspace.
Thanks in advance.
I am hoping to be able to use existing loft joists in a loft conversion without putting in a whole new load of joists. The middle 3 feet of the room is supported by staircase walls below, then if I put steels 6 feet further out on both sides (behind or below new roof supporting dwarf walls) and use hangers off them to support the existing joists (bit of damage to ceiling below but that needs underboarding anyway) that would give me a room 15 feet wide and lose no head height/ save on new/twinning joists.
The (Trada?) domestic span table I have goes as small as 97mm x 47mm joists at 400mm centres - the span given is 1.92 metres for C16. Mine are 85mm x 47mm at 360mm centres. (Timber is up to 150 years old, so am assuming it as equivalent to C16 not C22)
Does anyone know if there is a table for 85mm joists? Or a bit of software to do the calculation? Or is 85mm just too thin? It would save a fair bit on timber and work doing it my way, but most of all save valuable headspace.
Thanks in advance.