![]() Please note you must build the straps into blockwork as courses are being built. Straps to gable walls at rafter and ceiling level should be at centres less than 2m. Gable walls should be tied to roof timbers as illustrated in Diagram D4 below for stability. Please note: wall plate should have a width of at least 100 mm and a depth of at least 75 mm.ĭiagram D3 - Truss bearing strapping to walls Where wall plates are butt-joined, the trusses should be strapped (hold down straps) at no more than 400 mm centres on each side of the joint. Galvanised straps should be used to fix the wall plate to the masonry these straps should be at no more than 2 m centres or alternatively, the wall plate can be fixed using bolts at 1.2m centres. Trusses can be held down by fixing them directly to the wall plate using proprietary truss clips. Twisted galvanised vertical restraint straps are usually 30mm x 2.5 mm in cross section and should be included at the truss nearest the gable, and at 2 m maximum centres along the roof. EN : 2005 + A1: 2010 Eurocode 1 (Eurocode 1: Actions on structures - Part 1-4: General actions -Wind actions ). A separate design to calculate uplift should be carried out based on Irish Standard I.S. If a roof has a pitch of less than 15 degrees and/or the site wind speed is greater than 26 m/s and/or the building is located in an exposed location (and there is reason to believe high wind speeds may occur), additional vertical restraint straps may be required. Twisted Galvanised Vertical Restraint Straps ![]() Trusses should not be notched to seat on wall plate. 105-1: 1977 Wire and cut nails for building purposes, staggered and fixed at either side of the truss, should be used to fix each truss to the wall plate such that no damage to the punched metal plate fixings occurs. In some cases, fixing using nails may be permissible.Īt least 2 wire-round nails more than 100 mm in length and 4.5 mm diameter, and in accordance with I.S. Usually, the instructions will include fixing the trusses to the wall plate using proprietary truss clips or strapping to both the wall plate and the masonry wall. The manufacturer’s instructions should be followed when erecting trussed rafters. The overhangs illustrated are acceptable if the manufacturer’s recommendations are followed when bracing the rafters and joists.ĭiagram D2(a) - Diagram illustrating overhang of a truss Approval from the truss manufacturer must be sought where special design is necessary. If you have to splice more than one set of rafters, just make sure to stagger them on separate load-bearing beams or walls.Unless the trusses are specifically designed, the truss must be supported directly on the ceiling chord immediately below the intersection of joist and rafter. As an alternative to nailing these gusset plates to the rafters, you may also be able to find pre-manufactured metal splicing plates that are specifically designed to be used for this purpose. Using 16-penny nails, secure the gusset plates to either side of the rafter beams. Use pieces of lumber that are the same width as the rafter beams themselves and align them on either side of the rafter beams. To do this, you will use gusset plates on either side of the rafters. Once the rafters are placed against one another over a load-bearing beam or wall, you will be able to splice the beams together for structural integrity. ![]() Once you have 2 rafters aligned so that they meet in the middle, attach them to the place with 16-penny nails. Step 4 - Begin Aligning Raftersīeginning at one end of your structure, begin aligning rafters from opposite sloping sides of your roof so that they meet at the ridge of your house. As always, be careful when using your circular saw to avoid injury to yourself and damage to your rafters. You should be able to use your circular saw to make these cuts. Do this carefully in order to ensure a snug and secure fit. Step 3 - Notch RaftersĬut a bird's mouth notch in each rafter on the end that will rest on the lip of the exterior walls of your structure. Use a circular saw, measuring tape and a pencil to make sure that all rafters are cut to equivalent lengths. Again, it is important to make sure that all of your rafters are cut to the same length. Line the rafters up on rafter horses and cut them to length. It is important to make sure that the cuts are equal distances from one another and are all the same width and depth. Use a bevel square to measure the cuts in the ridge board where the rafters will be placed.
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