How would you do this roof?

[handirifle]

LD1
Hopefully I can answer most of your questions. I should have mentioned up front that the pic was not a finish plan drawing, it was originally made (by me) to give the truss co. an idea of what I had in mind. Knee braces were always in the planned construction. The posts are to be 8' high, with the header on top. The reason I mentioned the heavy duty header (6x10 or 6x12) was IF I decided to go with a glulam beam down the ridge with rafters down from that. The heavy header was theoretically to replace havine a center post support all the way to the foundation, in the front.


I still would use a 6x for the header, purely for looks.

The center post, in the rear, is on the same plane as the rear corner posts are. How could I extend this all the way to the top of the truss without cutting the trusses? I think I know what you're saying but could you elaborate a bit more on that? Please?

So, you believe a 2x4 16" O.C. spanning 9ft would support the roof load? Since I nevermentioned it, snow load is almost non existant here. Central coast of California. We see about one storm a year, and it usually drops a few inches. The roof is 6-12 pitch with 5/8 (or heavier if needed) sheathing and 15lb felt under comp shingles.

And lastly for the tripple in the front, I THINK, their original design had the third truss with vertical memembers for nailing on siding, since that is how they would do it for a house. I didn't ask that question, but it's my guess based on a later conversation, via email.

Would single trusses in the three areas, be made of 4x lumber? Remember we do not have snow loads here, but we do have to engineer for earthquakes, that might be it.

 

[LD1]

Typically aroundhere the end truss is on the outside of the posts and dot directally on top or them. this would keep the 3 posts on the back on the same plane. This is also to keep the 2" wide truss on the same plane as the 2x4 nailers if you were adding a wall. But the reason it needs it be extended is because you have to have something to add lareral strength to the open truss design you are wanting.
Example. Imagine taking 3 or 4 peices of 2x12 lumber and stand on end. Then nail a peice of plywood to the top. Now stand on it and rock back and forth. It wont take much at all to lay the "top heavy" 2x12's on their side and bend the nails. This is what you are trying to fight with trusses. Floor joists are the same way, that is why they have x-bracing between them. If want an open design with no cross braces, you have to extend the post onn the back.

As to the trusses. Using 4x lumber doesnt gain much at all. The strength comes from the depth. Example, a 4x4 truss would not be as strong as a 2x6 trusss built the same way. Typically that is how they add strength. By going to larger 2x lumber and not 4x. The only thing a 4x would gain would be lateral strength. Which may be required in your area due to the quakes you mentioned. I have no exp. with that. Just ask a few builders in your area if you can get trusses to span 18' on 9' centers. I'm sure someone can.

As to the 2x4's, yes you will be fine on 16" centers.
Here is a span table.http://www.msrlumber.org/spantables.pdf

I refrenced chart 10. with a 20psf live load and a 10psf dead load, and a l/240 deflection, a 2x4 will span the 9' no problem.

 

[MarkV]

My comment would be that I don't find standard manufactured trusses very esthetic left exposed. If I were building it I would build a conventional gable roof frame on 2' centers with 2x6 rafters and use collar ties every other rafter set above the 8' wall height for a taller ceiling feeling. The collar ties are also a great place to mount a fan light combination. One thing I have done in this type of structure is run a double layer of roof sheathing. For the first layer use T-111 with the finish side facing in and then layer it with 1/2" ply or OSB. It will give enough nailing surface to put shingles on the roof and leave an unmarred interior finish. You can sort of see the affect in the attached photo from our weekend house.

I have given up on open pavilions in my area. Between the birds, spiders and wasps we find a screened enclosure much nicer for the hot tub.

MarkV

 

[Kays Supply]

I used a cathedral truss system on my open back porch. It let me close it all in but still had the high ceiling. I put white washed pine tongue and groove boards on the ceiling. I put foam board above that. It keeps the heat from coming through in the hot summer. The gable is sided to match the house. Like they said, all screened it keeps the bugs out. I can pressure wash it all and it looks like new in short order every spring.

 

[Kays Supply]

I used a cathedral truss system on my open back porch. It let me close it all in but still had the high ceiling. I put white washed pine tongue and groove boards on the ceiling. I put foam board above that. It keeps the heat from coming through in the hot summer. The gable is sided to match the house. Like they said, all screened it keeps the bugs out. I can pressure wash it all and it looks like new in short order every spring.

 

[6sunset6]

You can get PT glue lams. I just priced some for a small bridge. Pricey but sometimes it is the way to go.
http://www.ilevel.com/literature/TJ-7102.pdf

 

[magicheater]

Why would you insulate it.?? A building with no walls.?? Why insulate.??

Building uses change, perhaps in the future it would be. When building plan for everything, you are in Maine, don't you?

 

[nickel plate]

Yes, no walls is no siding. There will only be the 7 posts. I do not want walls, as it is to be simply a roof, albeit a nice one, over the spa area. Picture one of the roof structures you see in parks oever the picknic tables. That's what this will be. More like a gazebo with an open ended gable roof.

I could simplify with the trusses every 24" OC, but that will greatly clutter the ceiling, in my opinion.

I plan on using grooved plywood, with the groove side facing down, to give the appearance of tongue and groove boards. All of this will be painted so it doesn't have to be quite as nice as T&G would be, just the look.

If you go with the grooved (4", 8" or 12"oc) plywood siding, do note that the sheathing span value is determined at the depth of the groove to the back side of the panel. 5/8" thick panel with a deep groove leaves you about 3/8" +- sheathing value. Not enough there to pass code as the thinnest roof sheathing starts at 7/16" thick.
Using stringers for nailing the roof sheathing does not take into consideration the required 8" oc edge nailing of the panels. Read the stamp on the back of your selected roof panel and you will probably see that the field needs to be nailed at 16"oc abiet this is for vertical sidewall application but again, stringers won't work. There used to be an 1-1/8" 4x8 grooved plywood panel decking that was made exactly for your application that spanned 48" thus no unsightly stringers at all but you will have to set the trusses at 48"oc.
Since your trusses will be exposed and if you do not paint them, tell the truss company not to spray paint your job name on the bottom chord of the truss package as that will give you another unsightly look once installed.
For what they do and the limited amount that you need, trusses are cheap. You can probably get a set of engineered single ply trusses with a larger bottom chord (2x6 or 2x8) that will span 48" oc.
Watch out for "shiners".

 

[LD1]

I would shy away from the gluelams unless you want to spend big $$$ and like the looks.

Gluelams do have their advantages such as being able to clear span greater distances without supports. And rock solid floors in new houses.

But for what you are doing, an 18' span with trusses is not hard to do with conventional lumber. Neither is the 9' span between posts and trusses.

Save your money cause gluelams are about 3x's the cost.

If you like the open look, get a scissor truss. Finish with your grooved plywood on the underside. It will give a vaulted ceiling look and yet it will still hide the trusses. Cause I agree with others that exposed conventional trusses dont look the greatest. If you still want the exposed truss look, and are willing to spen the $$, you cant beat the looks of large timber trusses IMO.

 

[handirifle]

My comment would be that I don't find standard manufactured trusses very esthetic left exposed. If I were building it I would build a conventional gable roof frame on 2' centers with 2x6 rafters and use collar ties every other rafter set above the 8' wall height for a taller ceiling feeling. The collar ties are also a great place to mount a fan light combination. One thing I have done in this type of structure is run a double layer of roof sheathing. For the first layer use T-111 with the finish side facing in and then layer it with 1/2" ply or OSB. It will give enough nailing surface to put shingles on the roof and leave an unmarred interior finish. You can sort of see the affect in the attached photo from our weekend house.

I have given up on open pavilions in my area. Between the birds, spiders and wasps we find a screened enclosure much nicer for the hot tub.

MarkV

MarkV

Nice looking setup there. I have given the rafters and collar ties some serious thought lately. You can even adjust them a bit higher from what I have read, anyway. Is your stained? Was that a spray on or brush on finish? If brush on, that would be a LOT of upkeep.

I could possibly end up enclosing this whole rig in the future, so really insulating the ceiling, or having the ability to, is not out of line in this case.

LD1
I do not recall ever seeing that type of setup here, interesting. Thanks for the span table info.

Kays supply
I have also considered the cathederal or scissor truss and enclosing it all. My wife is not super keen on the open beam idea, because of the spiders and webs.