Help Needed - Gazebo and decking project

[BluLi0ness]

Hey fellow builders!

I’m working on a decking gazebo area, roughly 7m x 2.4m, with a pitched gable roof at 13°. I’m using 150mm x 150mm posts, concreted in 600mm deep. The decking joists, roof rafters, ridge beam, and all joists are 150mm x 47mm C24 treated timber. The roof will have 18mm marine plywood, covered with Onduline Bardoline Roofing Shingles (minimum 12.5° slope).

On the left side, I’m adding a shed with exterior-grade plywood flooring instead of decking, and I’m considering feather edge cladding or shiplap if budget allows.

The third set of posts from the left will hold a table and chairs, so I avoided a joist across to the next post to keep it clear. Instead, I’ve joined the two rafters with 2 x 47mm x 150mm timbers. I’d like to know if this fix is structurally sound. Please check my attached plans for details.

Any advice on stability, especially for the 7m span and rafter join, would be appreciated. Located in High Wycombe, so clay soil and weather are factors. Thanks!

 

[johnny2007]

That 7m ridge beam might sag.
I would use an 8in but that's just me.
Or, use a bit more timber to create an A frame.
But I would still use an 8in for the ridge beam.

 

[johnny2007]

Or, looking at it again, an horizontal support beam from centre pillars with support for middle span of the ridge beam.

 

[BluLi0ness]

Hey, thanks for the reply. The ridge beam is actually split into 2. The first ridge beam is 2m and the second where this brace is 5m. Do you think it will be ok?

 

[johnny2007]

Hey, thanks for the reply. The ridge beam is actually split into 2. The first ridge beam is 2m and the second where this brace is 5m. Do you think it will be ok?

For a few pounds I would go for an 8x2

 

[vospy88]

Nice work! Your layout sounds really well thought out! I like that you left the joist clear for the table area and how you’ve split the ridge sounds smart for keeping that 5m span manageable. Using 150x47 C24 treated timber all the way through should give you good strength....especially with those posts concreted 600mm deep. Once you’ve got the structure sorted you might want to think about making the space more versatile. I’ve seen people use Surf & Turf accessories like sidewalls, canopy covers and even lighting to really finish a gazebo area nicely. Not structural stuff, but it makes the space feel high-end and ready to use without extra building work.