I'm tiling my shower, how should I construct it?

[Mudster]

Solid walls

If you have solid plastered walls, make sure they are straight and all plaster/render is solid and not hollow sounding. Tank the walls using BAL WP1 Tanking System and you're ready to tile.

Stud walls

The best product to use is tile backer board, this is a generic term for boards designed to be tiled to directly, they are all waterproof and uneffected by direct contact with water or condensation, Some provide a waterproof barrier and some don't.

The most easily accesible and cheapest of these products is Aquapanel produced by Knauf. Available in Wickes and B&Q is is a cement based class reinforced sheet 1200 x 900x 12.5mm or 2400 x 900mm x 12.5mm. It is impervious to water but does not create a waterproof barrier.

Aquapanel would still need to be tanked with BAL WP1 before it was tiled.

If you can avoid it, don't use plywood in a shower, marine, WBP or otherwise. Wood expands and contracts with heat and moisture, tiles don't like this and there are plenty of specialist products available to construct the shower correctly in the first place. A wall built in Aquapanel will actually cost less than the same amount of Marine Ply.