Older Terraced House - Roof Joists

Hi Seamanrob, I don't think ties spanning the joists are ordinarily necessary as a consequence of the new roof tile canopy. However, I would want to ensure the structural integrity of the rafters, to be satisfied they can bear the increased weight of the new tiles. It's likely the original timbers would have been chosen on the basis of the original slate weight over, which can be less than concrete tiles per m2. You could always run some batters along the tops of the joists, or g.i. straps, if you want to 'tie' them. But, if a Structural Engineer determined that the existing rafters needed beefing up, then it may also be suggested that you fix a sort of stud wall effort under the span of the rafters, thus supporting all the rafters. If this is done, you would of course 'tie' in the joists in doing so. So, if it were me, I would ask a competent Structural Enginner to calculate the weight of the new roof load and demonstrate if the existing timbers are capable of bearing this weight, and of course any other loads such as snow. Hope that helps, thanks, Jason.

your best is get a structural surveyor to have a look and see if the roof needs strengthening, by changing from slate to concrete you are increasing the weight on the roof significantly what did building regs say before they signed the job of. good luck Alex