My first post disappeared so I'm trying again with my two questions!
I'm building a covered alfresco area of 6m x 4m supported by timber stumps. Most are 100x100 but there are three 150x150 to support the roof load.
I've attached the subfloor layout to help visualise my questions!
1. The line of posts along the left side of the drawing sit about 500mm off the brickwork of the house so notching the double bearer into the posts could be difficult. Am I best to sit the bearers on top of the posts? If so what connectors should I use? Tie down strap and skew nails? Or could I use something like a triple grip?
2. I'm having trouble working out how the bearer and joist interact with the corner 150x150 posts (P1). I will notch out the front of the post to house the bearer, but then do I notch the side of the post directly above the front notch so that the joist can sit level on top of the bearer but somewhat inside the post? Feels like I'm cutting out a lot of that post given it is contiguous and runs up to support the roof load?
I am in Victoria if that makes any difference to codes or standards!
Welcome to the Bunnings Workshop community @ChrisKappa. It's great to have you join us and many thanks for your questions.
You should find this document from one of our suppliers helpful: Residential timber decks TDS. Within it are illustrations on effective ways to join bearers to posts. If you can't have the bearers fully or partially housed within the post you could then place them on top. To ensure they are adequately fixed to the post you might need to use a combination of triple grips, multi grips and/or connector plates.
I would be cautious about cutting into the 150 x 150mm posts supporting the roof at all. Was the roof and post dimensions engineered with the intention of them also being used to support a deck? I'd have thought additional posts would need to be installed at those points purely for the deck. If in doubt when connecting to an existing structure it would be best to seek the advice of an engineer for appropriate connection options.
Let me mention @ProjectPete to see if he could add to the conversation.
Please let me know if you need further information or had questions.
Thanks @MitchellMc that's really helpful.
All of our posts had been specified to sit in holes and concrete well above and beyond what's recommended with the 150x150s sitting in 450x1000mm holes. Even the building inspector was amazed at how big the holes had been specced. Our assumption was that this was for additional strength as they would support the bearers notched in as well as the roof.
The posts along that side are spaced approx 1500mm apart which also feels closer than needed.
We are assuming we aren't the first people to build something like this but have struggled to get a clear answer even after trawling through all the AS tables on spans and weight load. Doesn't seem to be anything specific about notching into posts supporting roof loads!
Just thought I'd add my own personal welcome to the Bunnings Workshop community and apologise for the trouble you had making your first post. Occasionally our automatic spam filter can be a little over zealous and quarantine legitimate posts like yours.
Please don't hesitate to reach out if you ever need assistance getting the most from the site, or ever have any feedback about how we can ensure Workshop is even more helpful to you.
All the best, we are looking forward to seeing how your alfresco area progresses.