Damp behind tiles in bathroom..dehumidifier time?

[edewakefield]

Hi folks,
Many thanks in advance for any advice anyone can give.

My little dilemma is that I believe I have damp in the bathroom walls behind the tiles. I thought I had dried out the walls sufficiently before tiling the bathroom.
I have concluded that using a dehumidifier would get the damp out and then I could treat the mould that has appeared in the grout. This has shown very badly in the bottom 18 inches of the shower tray in the shower end of that bathroom.The bathroom is a single story air cavity extension. Nine foot by five foot.
My questions are

a. What size dehumidifier would you recommend to get the damp out of the walls? As powerful as possible? 10 litre or much bigger?

b. What type of grout would you recommend to re grout affected parts of the shower? I have used bal on the floor tiles which seems better than the wall grout.

Many thanks,

Ede

 

[Richard C]

What makes you think you have damp behind the tiles, is this assumption just based on mould growth you can see on the surface of the grout lines? Do you have the obligatory extract fan fitted in the bathroom? It could be the mould is the result of condensation, poor ventilation & poor quality tiling products; you need to use an anti-bacterial grout such as BAL Microban or similar, cheap DIY tiling products are generally crap. I know it sounds tedious PITA but wiping the shower enclosure down with a rubber squeegee after each use helps to reduce mould growth tremendously.

If it is indeed damp behind the tiles then you need to establish where it’s coming from, entering the wall from outside, soaking into the grout lines from the front; are there any pipes behind the tiles? Either way, damp behind will have to evaporate through the thin grout lines, it will take weeks & a de-humidifier isn’t going to help much; if you don’t cure the cause, what happens when the damp returns? You say “I thought I had dried out the walls sufficiently before tiling”, does this mean there is a history of damp or is it a new extension you have tiled too quickly? What are the walls made of block & traditional plaster or dry lined plasterboard? What preparation was done to the walls before tiling? Are the tiles still firmly attached to the wall?