Not sure if you are aware that a structure like this is likely to require planning permission now. Basically any deck over 300mm above the ground falls under the regulations.
The text below is taken from the Timber Decking Association website.
For all but the simplest, low-level garden deck, property owners should satisfy themselves that planning regulations do not apply to their proposed structure.
In addition to contacting the Local Authority, we strongly recommend that you talk to all your neighbours about your plans. Neighbour objections are the most usual reason for planning refusal or enforcement notices after completion. Local Authorities can insist that structures are dismantled and removed where consent should have been obtained, but was not.
Hope that helps