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!

 

[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?

 

[pinenot]

Ok my man, as your obviously intent on doing this, you say when you cut the pairing rafter full length you would/will have problems getting it placed in beside the in situ one, why and at what point(s) do you envisage this? and can you sketch it?? ...pinenot

 

[paulmars]

three rafters where the roof sags have a measurable curve to them. 3rd one
is totally destroyed by termites. Every place that I touch it, it crumbles.

 

[pinenot]

The third rafter obviously should be replaced, from what you say it's offering no support to the roof, in fact it's possibly adding weight to the load i.e. it's weight pulling down vertically without offering load support. If this is impracticable, how can it be guaranteed inert?
That apart supporting the roof, indeed lifting in, can be achieved with Accrow props (that's what their called over here) 8' battens and chocks top and bottom, to spread the load and lifted very slowly once fully engaged to take out both the sag and and allow the new rafter(s) to be inserted. I've put the plural of rafter in brackets as I think you would be best inserting one thicker one or a pair doubled (might be easier to get in place) My reason for saying this is - if one rafter has completely gone, the sag and any stress damage will be at it's worst here, the extra support will aid good resettlement. As long as you lift with the spreading battens in place all should be able to lift to it's original positions, although you should keep an eye on the connections between the wall plate and the rafter joints for any lifting in which case steel clips/brackets should be fitted before proceeding...pinenot

 

[ban-all-sheds]

If I make it the same length as the existing ones, it wont fit.

What existing ones?

There will be no way to install it w/o removing the roof plankings.

What 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.

What block wall?

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?

Not really.

Are we supposed to have a clue WTH you are banging on about?