3/11/2024 0 Comments Max rafter tie span tableDoing the calcs based on a roof load of say 1.5kn/m2 and no actual load on the ceiling joists except for self weight the rafters sized at 50 x 200 would be more than twice structurally OK and deflection would be around 5mm of the allowable 11mm, and ceiling joists sized at 50 x 100 would have a deflection of 5.5mm against a 14mmm allowable. Put together 10 of these and lay them out in a line (with a nominal ridge plate incorporated for fixing purposes) and you have a roof structure. Is the ridge beam necessary if we have rafter ties? If so would vertical members from ridge to rafter tie on either end provide enough support - like a kind of king truss shape (assuming the lintel above each opening is sound)?Ĭlick to expand.Cannot see why a substantial ridge beam would be needed if going down the route of tied rafters, taking the OP dims and just laying out a triangular section (omitting the ridge plate bit) of 5.5m wide (ceiling joist) and 2nr 3.8m sloping sections (rafters) would give a structurally rigid frame albeit the distance from ceiling to ridge would only be 0.62m. The problem is that the gable end of the extension has a 4.5m wide patio door and the party wall end has a 1.5m archway into the main house. We would therefore need support for the beam each end. I have read multiple times that we will therefore need a ridge beam (we were planing on just a ridge plate at 2x8 to nail the rafters into although the suggested dimensions of the timber seem to be the same either way). We will fix plasterboard inside the rafters leaving most of the timber exposed inside. The rafters will then be covered with insulated steel panels. We will use 2圆 for the rafters and rafter tie. The span is 5.5m and depth from party wall to gable end is 3.6m.īecause of first floor windows we can only do a maximum 2 in 12 pitch. I am replacing my flat roof on rear extension and we are making it into a pitched gable roof for aesthetic and water draining reasons.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |