Hardie Backer Screws?

[Richardsuperstar]

I'm in the process of redoing my bathroom. Went to topps tiles and ordered tiles which have now been delivered. Obviously gave no thought to the weight and current plaster condition of wall once I pulled off the current tiles.

So here I am now with a shed of hardie Backer boards ready to go up to take the weight of the new tiles.

The issue I'm having is what screws do I use. Everything I read seems to say something different.

On two of the walls I am covering the 12.5mm plasterboard, the other 2 are block. All skimmed with plaster.

The hardie screws are all seem too short and most cement screws I find all seems to be in the US. Not much choice in the UK.

For the stud walls I'm thinking 5 x 50 or 60mm and the masonry something like 6 x 60.

So here are the thoughts I have racing around my head...

1. Am I meant to be using zinc or stainless screws? (My worry is stainless heads wont take the weight once tiles are on but anything else will corrode due to the alkaline content of the boards)
2. Do I use 4 or 5 mm wide screws on the stud walls? (My worry is the 5mm may break the boards but 4 seem too weak)
3. Do I use washers or with Hardiebacker is this not required? (Jewsons said I absolutely need them)
4. Is a gap left between boards on wall and the floor? (I've seen so many contradicting theories for this and being on the floor helps take the weight but leaves no room for any expansion which can crack tiles)


Any advice greatly appreciated.

 

[simplesteve]

Hi Richard.
I would question why you are using HardieBacker at all on the walls. It's far too heavy, and boards are too small and require loads and loads of screws. I'm guessing Topp s have been suggesting & pushing it. I have bought and used loads of both the 6 and 12 mil over the years, it is an excellent product, but I would only ever use it on floors.
If it were my job, I would plasterboard everything. I would baton the block wall to make a frame for plating it.

 

[Wayners]

I used wedi washers and drywall screws. 38mm

 

[simplesteve]

Drywall screws won't take the torque you need to get through a cement board. They'll snap.

 

[Wayners]

I drilled hole first. Never did much backer board work tbh, but there are self drilling drywall screws

 

[Richardsuperstar]

Don't drywall screws corrode due to the alkaline of the sheets?

 

[freddiemercurystwin]

James Hardie sell their own screws.

 

[Richardsuperstar]

They do but they all seem very short. 25 and 35mm

 

[simplesteve]

That’s because they’re ever only supposed to be screwed onto wood, eg floorboards/ joists/ frame on a wall. Screwfix ‘turbogolds’ for me every time

 

[Richardsuperstar]

That can't be entirely the case as this is on their website so if only meant to be screwed to joists or frames this could be quite confusing. Unfortunately as nice as this illustration is... No mention of screws.

Turbogold.. 4 or 5mm on studs?

 

[simplesteve]

But that drawing reinforces what I stated - it is screwed onto wood. Hence you only need 25 or 38mm screws, depending on 6mm or 12 mm board.
Deffo 4mm screws, the 5’s are much harder to get in, and get through your drill batteries.
But if you’re battening/ framing the wall ( as in the hardi drawing above) I would still use Plasterboard.

 

[Richardsuperstar]

In the diagram it shows them over boarding existing plasterboard. So assuming it's 12.5 plus 2-3 mm for the plaster and then the 6mm sheet and 1mm for adhesive wouldn't 35mmbe too short as that would only leave about 1cm going into the stud which is why I don't understand why they didn't make longer screws if they give this as an installation option.

Yeah you're right about the width thing. I just tried a 5mm on a board and it is a tadd hard to get through.

One thing I did notice though is that my nice new shiny yellow zinc screw came out silver. Not sure if that means all the protective coating had been ripped off or just the colour.

But the outcome of this so far is I'm going for 4mm Turbogold. But if I did go for stainless would 4mm be strong enough to take the weight of the board, adhesive and tiles at about 30-35kg/m2?

 

[simplesteve]

Do you know how the studs are fixed ?