An ambitious $138 million, 51-storey building proposed for South Perth near Perth Zoo known as the “timber tower” faces knockback this week for not having “achieved design excellence”. C6 promises to be the world’s tallest hybrid-timber building and Western Australia’s first to be “carbon negative”, but the Joint Development Assessment Panel will consider a recommendation for refusal at its Thursday meeting, calling it an “over-development” that has not adequately addressed authorities’ concerns. …The agenda for Thursday’s meeting says it has provided only 2.4 per cent deep soil area for tree planting, instead of the required 10 per cent. The development proposes “on-structure planting” to compensate, but “no demonstration of the viability of the proposed on-structure planting has been demonstrated,” the city noted in its assessment. It also noted that the banksias and peppermint trees proposed under the podium would have restricted access to sunlight and there was no plan for how they would survive.