Ahoy! Roof Experts

[Curtis Johnson]

Allen: Scissor trusses are usually for "vaulted" ceilings; cathedral is when you have the ceiling pitch paralleling the roof pitch (I think - I don't have an architectural dictionary). I have a project in WI that calls for parallel chord trusses with a 32" heel height. So, would you call that a "cathedral" ceiling or a "vaulted" ceiling?

[Curtis Johnson]

Paul: If you didn't have to put the pitch on the plans and just went up there and put up a roof that matched ridge heights, no one would ever no that the pitch wasn't 6:12 unless you told them. Not trying to promote shoddy work or anything like that - just trying to think of practical solutions. Good luck in your meeting.

[Allen42acj]

I have my wording wrong..
From his first post he said about the 3 1/2 inside pitch..
With trusses it is hard to adjust the pitch after they are made..

Just did a quick check for a ridge beam=4 ply 1 3/4"x18" LVLs...If I did it correct,big if..But I have done 24'x 24' family rooms that took 3 ply 18" or 4 ply 16" done by an engineer..

[pktraylor]

Sorry for the delay in my response.


Allen, in post #27 you have what I would think is the way to go. However, I forgot to mention that the existing roof is a hip and not a gable. This cuts the ridge distance down so I have not been able to duplicate what you.

I hate to admit it but I am stumped trying to get the client a good look. It looks great with a 4 pitch cathedrial and all will match. But, it turns out that the framers want to deal with trusses and not long rafters.


Paul

[Allen42acj]

Hi Paul
It's not the long rafters,it's the heavy ridge beam.And I don't like them to much either..

[ChiefChris]

I hate to admit it but I am stumped trying to get the client a good look. It looks great with a 4 pitch cathedrial and all will match. But, it turns out that the framers want to deal with trusses and not long rafters.
Paul

I guess you'll just have to get some real framers...

My framer handframed sheated and paperd this entire roof in 2 days with only 2 guys...when it was 11-20° outside. In fact 2 guys framed the whole project in only 1½ weeks..with an extra man to help stand the gable walls one day.

I think framers these days are just getting lazy....with all their pettibones, lifts, and what not...I still carry steel up a ladder on my shoulder to set it in a garage...

Paul - tell your framers you'll being them pizza one day if they do the hand-framing....

[Allen42acj]

3 ply 1 3/4"x 18" x 24"+ by myself..And Big Blue..
Still better than doing trusses alone.. Hate the domino effect..

[George Godwin]

Chris, - Up here, we sometimes call the ridge skylight you show as a Belvedere skylight. I was thinking that you could combine the exterior design feature of this type skylight with a Sun Tube. The Sun Tube is more energy responsible and no doubt brings in more light. Any thoughts or comments on this idea?

[ChiefChris]

PAUL - Go with a hand-framed roof...but use at least a 2x12 for the rafter so you can get R-38 in the ceiling the span is only about 17' at a 4 pitch (easliy with a 2x12spf@24" o.c.)... Keep in mind - the ridge bears no down load...the rafters are carrying all the load the ridge has only horizontal forces acting on it....So, the ridge can be a lesser material than the rafters. It's the rafters that need to consider deflection. You could use an 2x12spf for rafters with a 2x10 ridge in 10' lengths.

George, I've never heard of either of those terms...(ridge skylight or Belvedere skylight). I called this a cupola....

There's going to be a a huge chandiler hanging there...(same as the one in their great room pictured) - over a water fountain.

I'm not familiar with the sun-tube either - how would that incorperate?

[ChiefChris]

3 ply 1 3/4"x 18" x 24"+ by myself..And Big Blue..
Still better than doing trusses alone.. Hate the domino effect..

Gees Allen - why'd ya do that? You could have ran a single ply 2x10 across there and that would have been sufficient...

Your dormer on the front could be headed off between the rafters and the load on the rafters isn't carried by the ridge...

[George Godwin]

I'm not familiar with the sun-tube either - how would that incorporate?

Chris, - Putting your clients' chandelier element aside for a moment, my thought was that a Belvedere Skylight (Cupola) could be built as an exterior architectural interest item and could just sit on the roof or even house the exterior dome portion of the Sun Tube (Sun Pipe, Sun Tunnel, Sola Tube). But use a Sun Tube to bring light into the area below. There is no heat loss in winter nor heat gain in summer with a Sun Tube and I am sure the Sun Tube would bring in more light to the area below compared to the cupola skylight. Image attached. Any takers? Saves on electricity too.

[Allen42acj]

Chris
Here if you do not have rafter ties and collar ties a structural ridge is required..
Same roofs we did a few years back with just a 2x ridge.Not a safety issue,you might get cracks in the sheet rock..Ones of those things that should be a suggestion,not a code..
Inspectors want to see all the rafter hitting on a ridge..They don't like when the top cut is wider than the ridge..

[slatta]

"Keep in mind - the ridge bears no down load...the rafters are carrying all the load the ridge has only horizontal forces acting on it....So, the ridge can be a lesser material than the rafters"

WRONG!!!, the ridge has the most load on it, and it has to be a beam unless, as allen has already said, it has ceiling ties designed as a site built truss.

[Allen42acj]

Now I know who to blame=Chris
That gets Lew off the hook
Maybe George will be his lawyer

[ChiefChris]

Neal - the ridge bears no down load...it does bear the rafters - but only laterally. You can, in actuality, have rafter top-plumb cuts bearing on each other (back to front) and have the same load transfer as you would with a ridge....see image attached - you do not need a ridge structurally to hold the rafters up - they will support themselves against each other - what the ridge does is keep them laterally.

Allen, it is code now - with the 2006 codes you can't do a cathederal ceiling like that without collar ties within the upper 2/3 of the "attic" area. UNLESS you have it approved by an engineer, or specifically calculate the net and actions on that rafter system. (R802.5 and sub charts).

But - it's all subject to interpretation...