gaps between ply -overboarding question!

who leaves gaps between the ply sheets when overboarding a floor?

if so, can you tell me why you do it.

reason i ask is.. i was informed that you do it for expansion reasons.
i can see the reason for that because even if the boards are screwed and primed both sides then the joists and the flooring that the boards are screwed to can still expand BUT if tile adhesive bridges the gap when spreading and fixing then this gap is filled and therefore, inaffective..

also, if there is a 2mm gap between the boards, then i cant see the reason for using a brickbond laying technique either??

if i am wrong feel free to shoot me down, i am here to learn like everybody else.

[GazTech]

If the gap between boards is filled with flexi adhesive, like it will, it will take stress away fron the tile or the bond of adhesive and tile. Boards are recommended layed staggered. It gives better strength when stress is applied, you would question your brickie if your house bricks just sat on top of one another relying on the mortar to stop them from stressing out....Gaz

i understand the concept of staggering etc ...it was the reason for the gap that i found strange. a 2mm gap if filled and he pushed together under stress will push up the the addy between the boards causing upward pressure on the tiles. if the gap remained empty, then this would allow the room for movement. the whole concept of a gap is to allow for movement, this restricts the pupose imo..

[MrSpoon]

prime the underside of the ply before fixing in place, then sillicone seal around the edges of the boards and all the joints then tile

2 mm gap is fine wood exspands its got to move somewhere