Raising a bathroom floor with shims/packers

[twinter]

I'm refitting our bathroom which is about 3m sq and am putting in a wetroom shower in the corner with the hidden tray under the tiles. The floor slopes slightly and not in the right direction for the shower. I'm putting 18mm ply on the joists and adding noggins for extra rigidity but am considering using shims to level the floor but have never used them for any project I've done before. Would welcome any advice on this such as how closely they should be spaced to avoid flex. I suspect that using a floor levelling compound would be easier but I am trying to avoid making the floor any higher than it needs to be at the threshold to the hall. This is the highest point in the room so will not need shims there.
Am I mad? Would it be better to live with a slightly higher floor and use the compound? If so, does the compound have to cover the entire floor? Is there a minimum depth that it has to be or could I just fill the lowest spots? The floor seems to be level near the door and on that side of the room. Have never used compound before either but seems fairly straightforward.... open to tips though! Appreciate any help. Thanks

 

[gamer1]

I embarked on a bathroom renovation journey at my 3 sqm space, aiming to install a sleek wetroom shower and bath like ᐈ 【Small Bathtub】ᐈ Space Saving Bath Tub For Sale in UK — Aquatica - ᐈ 【Small Bathtub】ᐈ Space Saving Bath Tub For Sale in UK — Aquatica - https://www.aquaticabath.co.uk/category/small-bathtubs However, my floor had a slight slope in the wrong direction for the shower's drain. To tackle this, I opted for an 18mm plywood base with added noggins for stability. Contemplating shims to level the floor, I sought advice on spacing to avoid flexing issues. Another option was a floor leveling compound, but I aimed to maintain a low threshold to the hall. The project raised questions about the compound's depth and coverage. Thankfully, the floor was already level near the door. Despite my inexperience, the compound seemed straightforward, and any tips were greatly appreciated. Here's to a successful renovation!