how would I carry this out? Realizing it's possible you missed the reference to the spacing discrepancy earlier, but if there is an accepted method of achieving this joint given the difference, I'd like to know. Being the floor is 16oc and the roof 24oc. I understand this would clearly create a stronger connection. You suggest removal of what I had referred to as a "top plate" (sorry. While the application may be useless (or at least wouldn't help much), I wonder if you can shed some light on your suggested implementation. Understood that drywall weight is a drop in the bucket compared to that of snow. Having thought about a triangle losing it's corner, I can see where that system would fail, but if the "eve" corner fails, that means one of the other two would of had to fail first given the notched rafter, no? I'm certainly not one for doing more work than is necessary. Try to keep your nail forces in shear, not withdrawl. I would just lose the second "top plate" (that's what I think you called it) and connect the 2x4 to the side of the joist and the side of the rafter with multiple nails. With that said, what you are proposing also won't hurt your situation. If you have a lateral spreading problem, that corner of the triangle will simply open up and you will lose all of your strength. I can see that you are trying to create a triangle to resist the spreading, but triangles are only strong when all corners are strong connections. What you are proposing won't help much if there truly is a problem with lateral spreading. So really, you are only concerned about the additional load on the rafters due to drywall? I would look up the unit weight of drywall versus the unit weight of snow (and wind loads) to see if you should be worried.Īlso, if you wanted to strengthen the connection, I would look at the Simpson StrongTie website to see if they have a connector (besides the hurricane ties because they only resist uplift) that can strap the joists to the rafters: I understand why you are concerned but are you even sure that you have a problem? If the house is 100 years old, it surely has experienced snow loading before. I think we know enough to say it might be reasonable to proceed, but for the safety of your family (and future residents) you really need to pay an engineer to take a look. ![]() So it sounds like your joist spans are really only about 6 feet. But if you build a 4" wall/beam (actual dimension) in the middle, then the two spans are 11'-10, not 12'-0. So if you measure between the top plates and get 24 feet, then if you span it with a single joist/rafter, it's a 24 foot span. As you increase the pitch, the depth of the joist (measured in the direction of gravity) increases as well, so these factors offset each other. Rafter span is measured as the clear area between the top plate and the ridge board (or structural knee wall), parallel to the floor. When your roof has more pitch you get less snow/ice, but you get more wind. That includes the snow, the wind, the people, the furniture, and everything. The 50 lb/sq ft figure is the total live load. There are also programs online that will let you do the calculations, but you need to either know the species of the wood, or the design values for it. So if there's a load bearing wall in the center, then you only have about 6' spans.Īn engineer can calculate the values for your arbitrary sized rafters and joists. If your knee walls are located over load bearing walls, and those are in turn supported by an appropriate foundation, then you measure the spans from the wall location to the next support.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |