Wishing to use laserlite on top of the pitched roof. The beams will be 190*45 and the rafters and ledger beam that attaches to the fascia with the use of a angled rafter bracket(i seen them at bunnings dont know the exact name) will be 140*45. Too much work for my liking but still thanks for the idea. I specifically do not want to take out the existing colourbond posts and start from scratch since i have developped landscaping plants on the other side and in another area there is stencil concrete driveway. Posts will be 90*90 treated pine at 2.4mt spacing.

Soil is heavy clay, i can go wider to 450*450 post footing and go a little deeper to maybe 400 around the area the concrete base already is. Just some extra piece of info regarding the proposal. as the roof-frame is supported above openings by lintels, this will be your area of biggest concern considering this and the above, you may be better off overall building a free standing structure that doesn't attach to the house or the fence. it probably wouldnt be an issue for the wall itself - the issue will arise with openings in the wall. Silentc raises some good points about fixing to the wall & roof frame - certainly the code demands the span of the verandah be considered when designing the wall. your situation will determine whether this is an issue or not - i guess it depends on how much of a feature your fence is Something else to consider - if you are fixing your posts to the fence then the rafter joint to rafter-support beam or rafter to house-rafter or truss must allow for some movement or it will resolve itself along the fenceline by pulling/pushing it toward/away from the house. maybe even jack the fence up slightly to allow for settling. be sure to tamp the earth at the base of the footing well with something heavy, to minimise movement. I think you should be able to enlarge the fence footing without disturbing the existing concrete as long as it is not 'crumbly' - just dig around and enlarge, also go deeper underneath - it will pay to put some large gluts under the bottom rail of the fence to keep it in place while the new footing goes off & you dig the soil back in. alternatively you can use some post-anchors. you must allow for suitable drainage at the bottom of the post otherwise the rot will set in at the base of your posts. a consideration is the concrete-set timber post will be a durability issue because the conc shrinks and leaves a gap around the post which creates a water trap.

Rafter brackets for pergolas