The seat should be made of 2x4 like the uprights, for solidity. Cut the ends to 45° (converging) and lay upon and between the horizontal beams of the back skeleton, as to be parallel to the hypotenuse of the cornerpiece. In this case, I've also encroached the seat onto the front-left part of the skeleton so as to create a wider sitting space.
The roof is the only part of this structure that could be considered flimsy, being built of palletwood. I've built up the corners of the roof in layers, so that there's no vertical gap through which rain can fall, but plenty of spaces for vines to creep through.
The blank spaces can be filled in with ready-built trellis, or you can make angular shapes with 2x2 as I've done here.
And here it's best to customise it to your garden. The front-right side is facing into the shady side of a tree, so instead of putting in framework for all the climbers that won't be going there, I've put in a shelf. The brackets for the shelf are just the 45° offcuts from making the seat.
While the front-left side is where I'll be growing some kind of flowering vines (maybe clematis, maybe jasmine), so here I've put in the highest density of framework.
At the foot of the front-left side I've put in a box. It's open-bottomed to allow free access to the soil. It's pretty much just there to protect my vines against the mower and/or strimmer.
And now it's all stained and squared away in situ. I had to get a neighbour to help lift it, as it weighs ten stone and it's the approximate cubic volume of two adjacent phone boxes.
24m of 2x4 and 12m of 2x2. Total cost of the wood was about £80. Total cost of the whole build was about £100. Buying one of these in the shops would be £300-£400 easily.
Job done, I could do with a good cuppa.
Anybody know anything about chicken husbandry?