Visual weight. A second top rail at each corner makes the junction between the post and the overhead frame look heavier and more considered. It is the detail that distinguishes the double garden model from the standard garden version — visible from the garden looking at the structure, not just from underneath it.

The wall carries the rear load; the front posts carry the front. On a structure this size, a wall mounting is generally more stable than a freestanding arrangement of the same footprint because the rear fixing removes the need for rear posts and connects the structure directly to the building.

Yes, at the point of order. The back is already enclosed by the house wall. Screening can be added to the sides. Roof kits in clear, opal or bronze polycarbonate with white or brown glazing bars.

In Scotland a building warrant may be required depending on size and whether the structure is attached to the house. Checking with the local authority before ordering is advisable.

The double corner rail is an overhead feature — it sits at the top of the posts. The decking base sits at the bottom, supported on the post frame. The two are independent in terms of their fixing, and both are included with the structure.