I am hoping someone may have some advice. We have had this in place about 2 months and the timbers have bowed very badly. Both up, down and side ways. Not sure how to save this from here
Welcome to the Bunnings Workshop community @Houston. It's wonderful to have you join us, and many thanks for your question about treated Pine posts.
I'm sorry to hear that you've run into an issue with your project.
The issue you're experiencing likely has to do with 100 x 100mm posts not being kiln-dried. Unlike 88 x 88mm 1.8m F7 H4 KD Treated Pine Premium Posts that have gone through a drying process, your posts are considered wet and haven't been fully seasoned. They're a great budget-friendly product suitable for landscaping purposes. It appears the posts have warped considerably when used for this project. Perhaps @sandy_d's posts were less susceptible to this as she stained them, which potentially added some protection and allowed the timber to dry out at a slower rate.
Straightening those now would be a little difficult. If you were to wrap a ratchet strap around the two badly warped posts used on the back section, you could pull them back together. You'd then need to bolt them together with a threaded rod, using washers and nuts to hold them in place. The badly warped post on the seat section could be flipped up the other way and a weight placed in the middle, which might cause it to return to shape.
If you can return these posts to shape, I'd suggest applying exterior oil and stain to nourish the timber and provide some protection from the elements.
Please let me know if you have any questions.
The space you’ve created looks amazing!
I am so sorry to see the post has warped.
@MitchellMc has offered the best advice to try to straighten the beam. My seat has not warped but unfortunately a beam I used for my outdoor pergola has suffered the same fate.
I will be doing something similar to correct it by using a ratchet strap and supports to straighten it up.
I believe staining the timber posts has helped my seat not to warp.
I hope this helps.