#Rafter tie code#
There are footnotes to the code tables that explain by how much. If the rafter ties are moved up the rafter the rafter depth may have to be increased to counter the additional forces that can develop. They make a dandy ceiling and upper floor as well. Their job is to prevent the walls from spreading at the top. Rafter ties should never be installed lower down in the wall framing. That works well when applied after the sheathing nailed to the rafters of course, not just the sheathing.Ī rafter tie is located in the lower third, and are best if installed on the top plate of the walls, well nailed to the rafters which are well connected to the wall tops. Collar ties can be eliminated in a gable roof by using metal ties over the top of the ridge. They help hold the upper part of the roof together in high winds keep lift from pulling things apart. They are different and a stick constructed gable roof should have both of them.Ĭollar ties belong in the upper third and are best as close to the peak as possible. In recent years with the evolution (good and bad) of the construction codes there are now two generally recognized parts to a rafter assembly as well as the rafters themselves. Not to pick on your nomenclature Martian, but more to try to bring everyone into using the same definitions for components. I would consider using a plate on both sides, rather than a washer, to spread the load. If your collar ties were 2-3' from the peak, the loads would be much greater. You have a great deal of leverage countering the spread load at that point. Especially considering that your rafter ties (we call them 'collar ties' around here) are so far down the rafter. I like the look but I realize the connection to the rafter might get a little overloaded with nails.Ĭonsidering that your countering a sheer load, I wouldn't be worried about using bolts if you like the look. I was thinking of doubling up the tie, one on either side of the rafters that got ties, to look like this. I like nails though, so will probably stick with that. I read somewhere someone bolting their rafter ties instead of nailing them.
You're right, I guess there is the chance that snow will stick to the roof in certain circumstances! Even so, I'm not too worried.īolts vs nails. Not that the bolt may not be strong enough, but that the bolt concentrates the load on the wood fibers and the fibers may fail.
Are these the rafter ties? Usually bolts are not the best connections for wood joints. I am not able to draw the same metal image as you have on these 2x8's. Quoting: bobbotron.and doubled up 2x8 with bolted connection. But the rfater depth and spacing will be greater for 70 than 20 to 30 PSF. That will be a minimum of three 16D common (not box) with your pitch doesn't change even with 70 PSF snow load.
How many nails to use to connect the rafter ties to the rafters depends on snow load, the spacing of the rafters and the pitch. Be sure the walls are 100% plumb before nailing the ties in. So if it was me I'd design with that in mind and not skimp because the snow should slide off.Īs for rafter ties in the cathedral ceiling area, if the ties are only six inches above the top wall plates then they will still tie the walls together adequately. This was in northern NM not far from our property. And it snowed for hours and stayed well below freezing for a few days. Sleet turned to wet snow and added to the layer of pebbly ice. First it rained and sleeted and as the temperature dropped the sleet stuck to the metal roof. Case in point I have seen snow accumulate to a depth of something like 18 inches on a metal roof with a pitch of 8/12. It is not likely, but if the weather does just the right, or the wrong things, snow can build up. Quoting: bobbotronAs for snow load, we get a lot of snow here, but it's a metal roof I can't imagine anything sticking to this sucker.
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