Fixing Wedi Board to Plasterboard

[Tade]

Hi,

We're are currently having our bathroom redone, and have enlisted a plumber and tiler to do some of the work.

The wall that the bath/shower will be against has been stripped to the brick of all previous plaster. A plasterer has fixed plasterboard to the brick using dot and dab.

In hindsight we have realised this was probably a mistake, since it will be the bath/shower area and will be exposed to water. We've read that plasterboard can rot, when water gets through the grout between tiles.

The plumber and tiler have suggested that we put 8mm wedi board over the top of the plasterboard.

Before we go ahead with it we hoped to get some independent advice on here about it, if possible. Does this sound like a good solution? Will the plasterboard be okay if it is lined with this wedi board? Will the plasterboard be able to take the weight of the wedi board, and the tiles too? The tiles are large porcelain planks.

Many thanks in advance for any advice

 

[dilalio]

For tiles of a certain size and weight, you have to use a tile backer board such as Aqua panel or wedi, as it has a keyed matrix surface to grip the adhesive and tiles.
To fix this to the dot and dab I would use screws and plugs and the "film reel" type washers you can get from the arch forming section at Wickes (much cheaper than wedi washers) through the plasterboard, into the areas where the dabs are (shouldn't be hard to find with a drill bit) and blobs of gripfill every 350mm centres.

 

[Tade]

Thank you for your advice dilalio

So do you think its okay to put 8mm wedi tile backer board on top of the plasterboard, if we use those washers?

Or is it better to remove the plasterboard completely and replace with 12.5mm wedi tile backer board? Removing the plasterboard would be more work, but we don't want to do a job that we end up regretting in 5 years time. Or are we worrying unnecessarily?

Thanks

 

[dilalio]

As long as you fix it well, with the washers (they will prevent screws pulling through wedi board) and gripfill it will be fine.

I have bought these from Wickes before, but can't find them on their website. They are usually near the expanded metal mesh and archforming kits!

 

[Tade]

Thank you for the re-assurance

Do you think we should do anything about the existing plasterboard that is dab and dot? For example, mechanically fix this to the brick wall with screws and washers too? Or drill holes in the plasterboard and inject foam behind it? Just wondering how we assess whether the plasterboard is fixed to the wall well enough to take both the wedi backing board, and the large porcelain tiles.

Sorry for all the questions! Just want to be sure

 

[dilalio]

The weight will be a shear load: directly downwards! Not pulling away from wall so no real issue!
But, if you're concerned all you have to do, when you find the "dabs" that hold the plasterboard to the wall is use long enough screws, through the washers, so that both wedi board and plasterboard are fixed through and pinned to wall!

 

[Tade]

Thanks dilalio - good to know that force is downwards, so no issue for load bearing! That's the wall above the length of the bath sorted!


We have a stud wall for the shorter length of the bath, where the shower rail will be. On this stud wall will be a glass shower screen. The stud wall has three studs of 3 by 2 (the wrong way round). Hope you don't mind me asking the same question for this stud wall... do we need to be concerned about the loading bearing of glass shower screen? And will 12mm wedi board on stud wall be strong enough to support?

Many thanks

 

[dilalio]

On this wall, I would consider using 9 or 12mm ply with the 8mm wedi in front of it (again screwed and glued).
If your 2x3"s don't fall where you need them to be, to support valve, outlets, overhead arm and screen then add timber grounds to the studwork at relevant positions.

When tiling, I would also use a decent powdered adhesive, recommended by your tile supplier, rather than a premixed tub adhesive.

 

[Tade]

Thanks for you help dilalio

 

[dilalio]

Welcome