Hi
I have a mid terrace house, originally slate tiles replaced years ago with concrete causing roof to sag and slight historic bow to front elevation at roof line (the rafters don't join the ceiling joists directly, but join the wall plate which is 4-5 courses of brick above the joists) . There are four purlins in total (these are vertical rather than angled), one of the upper purlins has previously broken and a new one has been inserted next to it at a 45degree angle with a diagonal prop to support onto a weight bearing wall, pushing against another prop that has been inserted to support the other upper purlin.
Structural engineer report notes that the lower purlins are not supported and recommends that a timber beam be inserted from front to rear, resting on the weight bearing wall and upper and lower purlins be supported by vertical props to reduce their span (new purlin being rotated to make it vertical).
However builder wants to do this another way, putting 2 weight bearing 250x75 timber beams across the roof (just above ceiling joists) and installing diagonal props from these to support the lower purlins. My question is this: builder wants to insert the beams from the gable wall on the left side of property into the chimney of the right side (using the upper floor chimneys as these are not used) - right side has a loft conversion.
My query is about using the chimney in this way - is it reasonable practice?
Builder has apparently fixed similar properties in road that have had overloaded roofs (so should know what he's doing...)
I have a mid terrace house, originally slate tiles replaced years ago with concrete causing roof to sag and slight historic bow to front elevation at roof line (the rafters don't join the ceiling joists directly, but join the wall plate which is 4-5 courses of brick above the joists) . There are four purlins in total (these are vertical rather than angled), one of the upper purlins has previously broken and a new one has been inserted next to it at a 45degree angle with a diagonal prop to support onto a weight bearing wall, pushing against another prop that has been inserted to support the other upper purlin.
Structural engineer report notes that the lower purlins are not supported and recommends that a timber beam be inserted from front to rear, resting on the weight bearing wall and upper and lower purlins be supported by vertical props to reduce their span (new purlin being rotated to make it vertical).
However builder wants to do this another way, putting 2 weight bearing 250x75 timber beams across the roof (just above ceiling joists) and installing diagonal props from these to support the lower purlins. My question is this: builder wants to insert the beams from the gable wall on the left side of property into the chimney of the right side (using the upper floor chimneys as these are not used) - right side has a loft conversion.
My query is about using the chimney in this way - is it reasonable practice?
Builder has apparently fixed similar properties in road that have had overloaded roofs (so should know what he's doing...)
Maybe have a google around 
