Collar ties and shingles

[deabob11]

Now this really might be the last question!
We have framed and decked the roof, but we did not install the collar ties or sister boards to the rafters.  As of right now we only have rafters nailed to the ridge board and attached to the walls with simpson h-10 rafter ties.  We did not cut out a birdsmouth (sister boards go in later?).  
Can we install the shingles now?
or do we need to install the collar ties first? On the plans it says that "these can be installed after" and there is an arrow pointing towards the sister board.  Does this apply to the collar ties and 1/2 plywood gusset boards too?
thanks,
quickly progressing on my first building project!

[John Raabe]

With the rafters tied at the bottom with the metal brackets you are probably fine to sheath the roof and get the shingles up. You take a chance however on a big wind storm or heavy snow load. The collar ties greatly strengthen the rafters and triangulate the loads. Even if you got a few in there (say every third rafter pair) it would make quite a difference.

[deabob11]

well we forgot the circular saw and our compressor crapped out.  This is as far as we got on the day we decided to pay someone to shingle the roof.  only about 1/2 of one collar tie.  We are looking for someone to roof before this weekend and just wanted to make sure it was safe for a crew to be up there.
We are doing a 30yr timberline.  It was delivered with our lumber.  We are still looking for someone to come and put it on!

[John Raabe]

I'm sorry, no one here can determine if it is safe to be on that roof.

A prudent person might layout the staging and test the water... as you might a ladder setup... by jumping up and down. Wood will complain mightily long before it fails.

Be smart, be careful and take it one step at a time. If it doesn't feel solid then take the time to make it so before going on.

[John Raabe]

Note: If you are using my plans those collar ties are considerably higher than I show in the plans.

[deabob11]

"Re: 20x30 stock, change roof pitch (collar ties)
Reply #1 - 10/11/07 at 19:57:52  Quote   You can certainly lower the pitch. As for the exact measurements it is easiest to do with a chalk line and snap it out on the floor of the loft. Then cut a couple of rafters and try it out. When you like what you have use the rafters as a template.  

I would suggest pushing the collar tie higher (if you can) to give some usable headroom. A door header is only 6'-8" and the minimum (code) for a habitable room is 7'-6". Of course, if you go too low there is nothing left for the loft ceiling and you cannot triangulate the rafters with a collar tie. In that case you may have to go with a structural ridge beam and forget the collar ties.

The 45º roof slope gives the best trade-off, in my opinion, but it does require some extra care and planning when doing the roofing. "

We dropped the ridge beam by 2ft and dropped the collar ties by 1ft.  The top of the ridge beam is at 8' and the bottom of the collar ties are at 6'7".  There is not much room, but we were going to add a collar tie to every rafter after the roof was installed.  However, we could do that first and then have it roofed.  
Also, after the shingles were on we were going to add knee walls 4' in from each side to create storage in the loft.  
I figured that this would work.  I just didn't know if the shingles could be installed first and then do all this interior work once it is waterproof.
Any thoughts?
this is the 20x30 1.5 story.  We have made some minor changes (2x8 ridge beam, 9/12 roof pitch, knee walls, and a full loft).
I have another thread about changing the roof pitch.
Sound like all of this will work?

[John Raabe]

I think you will be fine getting the roof on first. However, there is no way I can analyze those changes and give you definitive structural advice.

The future kneewalls will help stiffen the roof so when you are done it will be plenty strong.

Just have the roofer check it out before they get up there. I expect they will not have a problem.

[deabob11]

thanks!