How to attach rafters to load bearing knee wall

[sirocosm]

What is the best way to connect a load bearing knee wall to rafters in a loft? If I cut the stud on an angle, and attach them directly to the rafters, any downward load will tend to push the tops of the studs into the room, so I am looking for the best method to prevent that. I don't want to cut into the rafters and bird's mouth them, they are not so deep (old 4x2s).

I thought about flat metal joiner plates nailed to the sides of the studs and rafters at the top, or metals straps across the front of the studs nailed to the rafters. I also thought about notching the front of the stud slightly at the top and attaching a binder to the rafters in front of the stud wall. The last option seems a bit trickier as the purlin it will be replacing is currently sagging, so I would like to level that in the process.

Is there a standard way to do this? Any other ideas?

 

[^woody^]

Birdsmouth them, otherwise your messing about with a timber cleat and two plates per rafter.

You can birdsmouth a 4" rafter no problem, it does not need to be the full width of the plate if you don't want to do that.

 

[sirocosm]

Thanks Woody. I just went and measured the rafters, and they are not 4x2s, but more like 3x2s, they are slightly over 8cm deep and 5cm wide. That does not leave much room for a birdsmouth, aren't they supposed to be no more than 1/4 the depth of the rafter? Even at 1/3rd, that only leaves 2.5-3cm max, the roof pitch is 42 degrees.

So I will probably have to come up with some other solution.

 

[cdbe]

Put the stud up the side and fix with 3x 4" woodscrews.

 

[^woody^]

If you notch it 25mm or so vertically (with the rafter at 42°), that will do and won't impact the section size.

 

[sirocosm]

Here are some options I was thinking about. If the rafters were a little deeper, I think I would birdsmouth them for sure, but 25mm does not seem like much to rest on, but maybe it would be OK with a few screws. However, I must say that I have never seen one done that small.

 

[catlad]

I would go with Woodys suggestion and notch an inch birdmouth in the rafters, if you still feel this is inadequate then use some half inch triangular ply gussets to strengthen the connection further.

 

[noseall]

, but 25mm does not seem like much to rest on, but maybe it would be OK with a few screws. However, I must say that I have never seen one done that small.

Most of the roofs on our street are like that.

 

[^woody^]

Most of the roofs on our street are like that.

I must have done those ones then. Are they still up by chance?

 

[noseall]

. Are they still up by chance?

Solid as the day they were built....