Damp cause of stains ?

[fad]

I've just started a job where the client has has me to replace the tiles because the tiles and grout in particular are stained.
Having taken the tiles off I noticed that a small section of the plywood backing is damp :yikes: ( this is after having removed the adhesive).
Firstly could this be the cause of the grout stains ?
Secondly should I just let it dry out naturally or can I use something to help it along ?
Thirdly, I thougth the backing was plasterboard, so I got some mapeigrip plus for the tiles (small ceramic) but would a bagged addy be better for plywood ?
Any suggestions appreciated.

 

[Ajax123]

First question I would be asking is why is it damp in the first place. Unless this is addressed you can dry it out as many times as you like and the problem wont go away.

 

[White Room]

Had this once with ply, the resin in the ply seems to draw thru to the grout when it gets wet.

I would tank it personally to stop it happening again and use a powder adhesive

 

[jay]

hi what area are tiles in (shower ,floor .bath) what color is the staining:8:

 

[White Room]

The staining I had once was brown on white grout:yikes:

 

[fad]

Good point about the damp ! apparently they had a leak in the past but it got sorted. There was no tanking so I thought it might simply have been water finding its way through.

 

[fad]

The staining is a kind of brown colour now that I come to think of it. This is in a shower area.

 

[jay]

Had this once with ply, the resin in the ply seems to draw thru to the grout when it gets wet.

I would tank it personally to stop it happening again and use a powder adhesive

and this would be your best answer spot on whitebeam