Silicon or grout for wet area tiles?

Ok, I've had a good read through these forums looking for an answer and seem to have got myself confused.....

I am currently refitting our bathroom, we have a concealed shower above the bath.
The walls around the bath have been clad in Aquapanel cement board, and the joins sealed and taped.
My question is: what do I use to fill the gaps between the tiles?
1 Waterproof grout
2 Silicon
3 Something else


As I said, I've read through the forums and got confused with people interchanging terms like grout, silicone and caulk!

To be clear, to me:
Silicon = the stuff that comes in a tube, applied with a caulking gun that stinks to high heaven and turns into a rubbery substance when cured.
Caulk = comes in a tube and applied with a caulking gun, however barely smells and dries solid, like filler you'd use on a plaster wall.
Grout = The powdered or ready mixed paste normally used between tiles, gritty feel when wet but dries solid.

Any advice is much appreciated!

Grout, definately.

Silicon should only be used for the corners\join with the bath, and is kind of optional. As you've already gathered none of these are the waterproofing layer, the cement board does that. Grout can\will let a small amount of water pass through it, but it wont break down. Failures often come from plasterboard breaking down behind the tile, which you wont have an issue with.

Silicone is great stuff, bit prone to black mould, hard\impossible to clean, relatively expensive and a bugger to work with. Grout will give you a nice neat professional finish.

Caulk should be ignored for anything other than decorating\paint.

Get yourself a good quality, professional (BAL, Mapei etc) flexible powdered grout, and you wont go far wrong

Thanks tpt!

As a side question based on your reply, why does everyone rrecommend powdered grout rather than readymix for wet areas? It's the only consistant point I've seen on here.

Its generally because its much better to work with, and usually better quality. a lot of the ready mixed grouts are aimed mostly at the DIY trade, they can sometimes be oil based and a hell of a job to clean off, or if not they tend to be a nasty consistency and sometimes dry with uneven colour. its really easy to mix powder grout if you take your time and follow the instructions

I would still silicone the edges after you grout,they will crack.

I'm using plastic trims on the edges.... does that still count?

You should use waterproof grout for the tiles but always silicone the joints where walls meet walls / floors / shower bases etc.

Different substrates expand / contract at different rates and grout will crack and leak - Silicone is very flexible & won't crack.

So for your application silicone the internal wall joints and where the tiles meet the bath. Leave a ~3mm grout spaced gap for the silicone so that you get a good join and fill the bath with water before you silicone around it (and leave it full until the silicone's dry) so that the gap is at its maximum.