But on the back wall you'd have to either run some gable end braces down to the old 8' top plate, or run some tall studs up to the new ceiling height to brace there and keep a clean ceiling.Īlso, does the driveway location play in how far you move the door over, as you don't want to have a little jog to negotiate pulling in and out. So on the door end a portal frame could counter the hinge. If you move your gable end bracing to the new higher top plate height, you've created a hinge 8'. For the rafter ties, spanning 24' across with no storage you are at 2x10s at every rafter.Īlso, the existing walls on both gable ends have top plates 8' which will now be below a higher ceiling. 67 of 18'-2" is around 12' span, and assuming the garage width is about 24' - getting close so check your numbers on how high you can raise the ties. Minimum footing size tables are revised to more accurately reflect current practice. Component and cladding wind pressures in Table R301.2(2) are updated for new design wind speeds and hip or gable roof profiles. So if it's 2x8 rafters, if you raise rafter ties 1/3 then. Ceiling joists shall be sized based on the joist spans in Tables R802.5.1(1) and R802.5.1(2). Not sure if the sentences are the same thought saying new 2x8 rafter ties would span 18'-2", or if you switched gears and are saying the existing rafters are 2x8 and span 18'-2" for your snow load (guessing 20psf?). Other ideas, consider a jack shaft garage door opener to save some header space. Simpson strong tie makes some simple brackets to support the header attachment into the vertical wall making for a very strong gable end. There is also a series of videos showing homes and garages destroyed due to high side wind loads and narrow or poorly constructed garage portal walls. Also see the journal of light construction (JLC) and the Engineered Wood Association. Search "portal frame at garage door opening" for information on minimum wall widths and proper construction methods. Current building codes improve upon that situation. Past construction practices left "portal walls" weak and prone to racking. However, check how the side walls are constructed and improve them if necessary. You are improving the situation by centering the door and making the side walls at the gable end wider. Too narrow a side wall or poorly constructed wall and you risk the structure racking and collapsing due to side wind loads, earthquakes, attic loads or snow loads. ![]() ![]() Table R802.5.1 (2) Rafter Spans for Common Lumber Species. Table R802.5.1 (1) Rafter Spans for Common Lumber Species. One item not mentioned is the finished width dimension and construction of the two garage side walls facing you in the picture. 2020 Florida Building Code, Residential, 7th Edition - CHAPTER 8 ROOF-CEILING CONSTRUCTION - R802.5 Allowable rafter spans. As others have stated you can increase the height of the header on the gable.
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