Question about Cathedral framing for 1 1/2 story

[jballone]

Got a couple of quick questions:

1.  I plan on building the story and half cabin (20x30).  The loft will be half floored and the area over the living room & dining room will be open to above.  Is it fine to frame the roof using the cathedral framing option and having the rafter ties every 4ft in the open section attached to the top plate (as specified in the plans) and having the loft floor serve as the rafter ties even though it would be 12" below the ridge plate?

2.  Can you scarf the ridge beam from 2 boards?

Thanks,
Joe

[MarkAndDebbie]

1. I hope so - that is my plan. (We'll get a more authoritative answer soon I'm sure). I was also going to collar ties (a few feet down from the ridge) above the loft part as well.

2. Yes. It's in the Nash book (and maybe the Wagner as well). They cut both boards along the vertical at 45 deg. Then nail through the joint. They nailed boards parallel to the side of the ridge till the rafters held the weight of the ridge. Put a rafter at the joint (or rather put the joint where a rafter will go). For my shed I put the ridge together on the ground and then raised it. PEG has shown a couple of times putting it together in stages in place - I think I'll do that for the longer ridge.  

When I first put it together I thought "there is no  way that will stay together while I lift it." So I got some simpson plates with like 50 wholes in them thinking I would nail from one side through the other and cinch it over  . No way I could drive 10 nails perfectly perpendicular - much less 50. By the time I was done (ready to try something else) the plate was not in a returnable condition. I then put some of those non structural splice things your just hammer in - top bottom and sides leaving enough room to nail through for the rafter. That kept it together while I raised it. Keeping it vertical helped a lot as well.

More info than you asked for - just a time of confession.

[jballone]

My thought for the ridge beam was to scarf it together and then sandwich it between (2) 2x's.  I planned on putting the joint between the rafters.  Will this work?

Joe

[MountainDon]

My thought for the ridge beam was to scarf it together and then sandwich it between (2) 2x's.  I planned on putting the joint between the rafters.  Will this work? Joe

It'll work but it's not necessary. Once the roof is framed and sheathed the joint doesn't matter at all. Get it erected and you're home free.

If you insist on doing that you'll have to bevel the upper edges of the reinforcement 2x's, or position them down a bit, to allow the sheathing to fit without a bump.

[peg_688]

It's called either a ridge board or just "the ridge" unless it's a true beam  as in a 3 by or thicker as in a real beam.

Heres a ridge beam,



Generally the rafters sit on top of are part way on top of a ridge beam . A beam is meant to span the full lenght of a building , or at least to appear to  full span. As in it sits on top of a post at the joint. This ridge beam could just as well been a 2x12 BUT this ridge  beam was / is exposed inside the room for looks . A covered over 2x12 would have worked , in this case, althought collar ties are generally used with a 2 by ridge board.  The collar ties prevent the wall spreading , which in turn prevents the ridge become "sway backed " / sagged.

 In your case the ridge board can be spliced , do it "on lay out" put your splice half on one pair   half on the other , dead center on normal rafter layout.

 It will / should look similar to this ,




G/L PEG

 

[jballone]

I guess I'm still confused?  Are collar ties necessary?  The cathedral plans do not have them, just rafter ties.  Also, I still need an answer in regards to using the loft floor trusses to act as rafter ties.

Thanks for the help!

[jraabe]

In the open section of the ceiling, where you are not tying the walls together with the loft joists, the rafter ties are needed (as shown in the plans booklet p.9). Collar ties are not needed [highlight]in addition[/highlight] to the rafter ties.

In the section where you have the loft floor (see Loft Plan, sht 3) you will tie the walls and the floor system together using either of the two details on sht 5, "Loft Floor Details". You have the option of the standard drywall ceiling with joists @ 16" o/c [highlight]OR[/highlight] a built-up beam and decking system for a wood ceiling below. Either one of these will tie the walls into the roof system above. Also, in this section of the loft you should have collar ties on each rafter at the ceiling height or the site built truss sht. 4. This has the effect of diminishing the outward thrust on the walls.

[jballone]

JOHN:

You seem to contradict yourself in your answer, can you please clarify.  What I'm trying to accomplish is to have the same ceiling line (cathedral 12/12 pitch) run the entire inside length of the cabin.  I'm trying to avoid the use of collar ties to accomplish this.  Will the loft floor joists act in the same manner as the rafter ties in the open area above the living room, thus eliminating the need for collar ties in the floored loft area.  It seems odd to have collar ties over one section.

And if you need collar ties over the floored loft area, where the walls are anchored ever 16" with floor trusses, why aren't collar ties needed over the open area, where the walls are anchored by rafter ties every 4 ft'.

Thanks for all the help!  I love the plans but I just can't get past this problem.
Joe

[peg_688]

You'll need those collar ties in the loft area as that's living space , moving bodys , weight , thrust, etc  moving about wanting to wrack those walls apart.  The collar ties make a triangle which adds a lot of strenght , wracking resistance.  

In the open / vaulted area your "live loads" are well below at the first floor level not elavated 8' up the wall.  So greatly reduce strenght wracking resistance is required.  I'd still recomend collar ties if it where me building it. I could be over ruled , it has happened. Generally I get told "Yanno the house feels a little whimpy in that great room! We should have used something to prevent that!"   I just smile and remind them of what they have "forgotten "

 Another thought on this is that 12 in 12 pitch and that angle you'll have to finish , well unless the place is not getting a "finished" ceiling will be a PITA to tape , paint , run T&G  boards etc. Also hanging any lighting or ceiling paddle fans will also be a PITA , do able yes , But avoidable if you drop that whole lenght vault down to a 3 or 4' flat ceiling on those collar ties.  

[jraabe]

Peg and I are in agreement. If you want to do the higher sidewall in the loft you should use the collar ties to restrict the loading on the side wall. You may be able to eliminate these if you have low wind loads and little chance of earthquake but that would be a local issue you should run to ground there.

Perhaps this will make it simpler to do what you want...

If you set all your rafters on the top plate of the wall, and then nail the floor joists to those rafters at the plate line AND double the rafter ties (4' o/c) in the open (non-loft) area then you will not need collar ties and can go from the ridge board to the wall plate with ties across the rafters. The downside is this eliminates the knee wall at the loft.

[jballone]

PEG & JOHN:

Thanks for that explaination, it makes sense to me now  

I'll put the collar ties all the way across for uniformity & strength.

Thanks again,
Joe