I want to build a 6 sided gazebo but am having difficulty finding design details on the roof trusses. Not the trusses so much, but how to support them all in the center. The roof will be asphalt shingles over OSB and supported on 6 4x4s. What's the best way to build a center support? Any useful suggestions will be greatly appreciated.
Jim
Haven't built a gazebo but I did recently buy a book on the topic for a gift and can heartily recommend "Building the Perfect Gazebo" by David Schiff.
-Leuf
This might help.
Look at the Simpson "Strong-Tie" item GT6Z at the following URL:
Jim,
The framing for a gazebo type structure involves making the rafters into a "three hinged arch" (using the GT6Z connector Jack talks about)
- these 'hinges' being the connections at the bottom (where it connects to the posts) and at the peak. That means that the GT2Z connector (see link below) is equally important as the peak connection. All three connections - together - provide the strength. Then, by adding the OSB decking, you create a *diaphram* that also adds stength (think: "What must happen to the OSB for the rafters to fall?" and you'll be able to visualize the 'system'). If you were real concerned, you could put in a temporary support at the peak until you got the OSB installed (I'd keep it in place until the roof shingles are also installed). It should be plenty robust enough. Note that the Simpson detail shows
*two* of the GT6Zs (at the peak) - one on top of the rafters and one underneath.However, if you want to beef it up even more, use (as you initially noted) a *truss* system - making 6 little right triangle truss elements (made up of a top 'chord' (the rafter), a bottom 'chord' (the 'ceiling joist', if you will) and a vertical 'king post' there at the center - all tied together with Simpson clips or some plywood side plates). In this case, for these trusses to fail, the bottom chords of all 6 would have to move *out* (towards the posts) from the center point. So, to stop that, simply use a GT6Z there at the bottom to tie all these bottom chords in place (this would, in effect, be moving the bottom GT6Z from the situation in the previous paragraph down to the bottom plane of the trusses.) Again, make sure to use those GT2Zs out at each and every post - to tie the trusses to the posts securely. Then deck and shingle as noted above. This approach would be considerably more robust than the approach above.
The *important* thing in either of these approaches is the
*connections* - compromise on tieing everything together and you can seriously undermine the structural integrity of the whole system - and it is the *system* that carries the loads.-- john - Registered Architect - GA (normal disclaimers apply - do it smart, don't compromise, think - remember, "quality is your friend")
Nova wrote:
If you use construction adhesive to secure the roof decking to the rafters - it will really make a difference strength-wise.
What diameter and roof pitch did you want? Two level roof? Cupola?
There's a lot of guys (at least around here) selling gazebos/kits and have full sized ones at local garden centres, lumber yards etc.
Why not go check one out for ideas?
Thanks to all for the links and the information. I now have a good idea on how to proceed.
Regards, Jim
I agree that construction adhesive can help and add some strength. I generally use it on personal projects as well. The problem is -
*no*body (i.e. the manufacturers) will "put a number" on what the benefit of these adhesives are - and, without an 'actual number' (to do a proper structural design), the only rational number is "zero".Use it? Sure! Will it help? Sure. How much? Nobody knows. (and, that is somewhat to be expected, because these things generally need a precise control of the process and that generally doesn't happen in everyday practice).
Therefore, simply consider it as "insurance".
-- john.
resrfglc wrote:
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