How to install rafter sister?

[paulmars]

If I make it the same length as the existing ones, it wont fit. There will be no way to install it w/o removing the roof plankings.

My only idea is to make it shorter and cut the piece that sits on the block
wall, cut the angle 1.5" higher. This will allow me to slide it in further,
then lift up the ridge end and pull it into place. Then place a 2x4 below
the angle cut on the block wall side. Clear?

My jpg shows a drawing of existing rafter with the red line how Im thinking
of cutting the sister. It would be weaker, but this is all that i can think
of. If I do this I will attach it with screws and glue to the block wall top wood and bolt it to the existing rafter two bolts 1' apart at each end.

better ideas?

pics and my drawing:

http://s276.photobucket.com/user/paulsmars/library/RAFTER SISTER?sort=3&page=1

please ignore the 1st incorrect jpg drawing. I cant figure out how to delete it. No wonder I stopped using photobucket a long time ago!

 

[MikeHalloran]

Why are you sistering the rafters?

To just stiffen them up a bit, you'd only have to sister the middle half or so.

If you want to bridge that big-ass knot and similar oddities, yeah, I'd go for almost full length. I think the slide-in-key/ Chinese puzzle detail at the wall header may be overkill, and I might leave the top a bit short of the ridge beam, without a matching miter

Is that Liquid Nails holding the rafters to the ridge beam?
That stuff doesn't work at all for me, but it worked great everywhere for the prior owner of my house. Maybe it's been reformulated...





Mike Halloran
Pembroke Pines, FL, USA

 

[paulmars]

sagging rafter. subfloor adhesive.

 

[AELLC]

Without even looking at the pics, you can help a sagging rafter by applying a Simpson strap to the bottom, temporarily give the rafter a little nudge upwards about midspan, and use screws instead of nails.

The definition of a structural engineer: overdesign by a factor of 1.999, instead of the usual 2.

 

[AELLC]

Also - if there is only the slightest slackness in the strap, it won't work, and definitely don't use the coil straps.

The definition of a structural engineer: overdesign by a factor of 1.999, instead of the usual 2.

 

[paulmars]

what about the sag? Im gunna have to PUSH it flat with this new rafter. Will not the old sagging rafter push against the new, maybe sagging it too?

 

[AELLC]

The net sag will be less, and the stresses much lower

The definition of a structural engineer: overdesign by a factor of 1.999, instead of the usual 2.

 

[paulmars]

yes, but still over time...

AELLC (Structural)
28 Mar 14 10:35
The net sag will be less, and the stresses much lower

and I dont understand:
Without even looking at the pics, you can help a sagging rafter by applying a Simpson strap to the bottom, temporarily give the rafter a little nudge upwards about midspan, and use screws instead of nails.

 

[AELLC]

I was lazy because you didn't seem to respond favourably to my replies in your other post, recently.

The definition of a structural engineer: overdesign by a factor of 1.999, instead of the usual 2.

 

[paulmars]

?

 

[AELLC]

If you apply the strap to an already-sagging joist, it will not be stressed until further defelction occurs, and is basically useless.

Devise some method of propping up that sagging rafter before you fasten the strap with the screws.

The definition of a structural engineer: overdesign by a factor of 1.999, instead of the usual 2.

 

[ztengguy]

Seems a bit off to me.

 

[paulmars]

STRAP? iM SISTERING THE ENTIRE RAFTER. Who did that again? Set my cap locks.

 

[CELinOttawa]

Okay, I think you received very good advice in the previous thread, and at this point you're in way over your head.

HIRE A LOCAL STRUCTURAL ENGINEER.

 

[paulmars]

Thank you.