WBP ply or backer board?

[HighlandWoman]

Hello, long time lurker and kinda first time poster looking for advice on bathroom planning.

 

TL;DR: Will tile backer board fixed over brickwork hold grab rails or is WBP better?

 

My bathroom currently has been lined with plywood and then tiled. I am looking to remove the tiles and reconfigure so I have a larger shower and a Japanese style sit bath. The shower and bath will run along an internal party wall which might be brick (assuming it is the same as in the kitchen. Previously the original lime plaster was chopped out and at least half the wall replaced with ply and then tiled over.  The other end of the wall looks like it might be plasterboard.

 

As this wall is where the shower (with concealed piping) and bath will be, it is going to be tiled to about a foot above the shower head (ceilings are 3.4m) and the shower opening will be at one end of the bathroom, with the bath accessed via steps built into the other end of the shower. These steps will create a shower seat as well. I want to attach a couple of really strong grab rails at the transition between shower and bath. I'm not convinced that tile backing boards are up to the job of holding a grab rail and I'm not sure where the rail will go to put studs in place. I can drill all the way through to the brickwork, but if I hit mortar, then I'm not convinced that is going to be safe.

 

Whatever I use, I plan on completely tanking the shower/bath area.  I have attached a rough plan but it's not to scale and I struggle toggling this kind of stuff. For the record the bath is 100cm high and I have checked I can get a Gerberit wall cistern in there which will service a washlet.

[Temp]

Not sure about grab rails but tile and stone over 12mm Hardiebacker board seems to hold things like soap dishes and shower head rails well without needing to find studs.

 

I think 12mm of anything might be marginal for grab rails? Can you drill through into the brick?

[HighlandWoman]

Hi Temp, thanks for responding. I would hope to hit brick behind whatever I use, but the bricks in the room below are kind of honeycomb (it's an old house). I wouldn't trust them to take weight. This is why I thought WBP ply at 18mm. I don't know how structurally sound Hardie board is if it has drill holes fairly close together because I've never used it. I mean plasterboard wouldn't take it. 

[Nickfromwales]

11 hours ago, HighlandWoman said:

Hi Temp, thanks for responding. I would hope to hit brick behind whatever I use, but the bricks in the room below are kind of honeycomb (it's an old house). I wouldn't trust them to take weight. This is why I thought WBP ply at 18mm. I don't know how structurally sound Hardie board is if it has drill holes fairly close together because I've never used it. I mean plasterboard wouldn't take it. 

Go for 25mm plywood? These grab rails may have to prevent you from taking a tumble, so I’d have this done properly first as last.

 

If you tank the plywood then you can tile straight to it with a flexible, cementitious tile adhesive. Do NOT let anyone use ready mixed acrylic tile adhesive here, whatever you do!!! This stuff is crap, regardless of what promises are written on the side of the tubs.

[Mr Punter]

17 minutes ago, Nickfromwales said:

Go for 25mm plywood?

 

They are seriously heavy.  2 man lift.

[-rick-]

31 minutes ago, Nickfromwales said:

Go for 25mm plywood?

 

I thought I'd read that 18mm was the standard for accessible (or convertable) bathrooms (attached to wall at 400mm centres IIRC).

[Nickfromwales]

17 minutes ago, Mr Punter said:

 

They are seriously heavy.  2 man lift.

And?

[Nickfromwales]

14 minutes ago, -rick- said:

 

I thought I'd read that 18mm was the standard for accessible (or convertable) bathrooms (attached to wall at 400mm centres IIRC).

If I was going to buy 18mm ply and then pay someone to fit 18mm ply, I’d at least want to consider going to 25mm and see if it was a much better, long term solution, than to find 18mm was just ‘ok’.

 

UK b regs is a “standard” it’s just a totally crap standard and the worst job you can do legally. Nothing to strive for!!

 

If a few more £10’s can make an ok job into a great one, and then that negates the plasterboard, then on paper it would be cheaper and better?

[JohnMo]

2 hours ago, Nickfromwales said:

25mm plywood?

Our 12 degs roof is covered in the stuff, some off cuts have been sat outside for 5 years now. Not covered allowed to get wet. It's still in pretty good condition, considering.

[SimonD]

1 hour ago, Nickfromwales said:

If I was going to buy 18mm ply and then pay someone to fit 18mm ply, I’d at least want to consider going to 25mm and see if it was a much better, long term solution, than to find 18mm was just ‘ok’.

 

I think it depends on the type of plywood. If it's a decent quality birch ply at 18mm I'd personally have no problems compared to a generic 25mm far eastern hardwood plywood as it will hold the screws. The last time I got some 25mm hardwood stuff, it was terrible, full of voids etc. Just a very non scientific observation was that I left some interior grade 15mm birch plywood outside for over a year and it just went grey. I also left some generic far eastern exterior grade hardwood 18mm outside which delaminated in a few months over winter.

[Nickfromwales]

As always, you get what you pay for  

 

@HighlandWoman ask questions of the quality of the plywood, and get a good installer.

[Mr Punter]

2 hours ago, Nickfromwales said:

And?

You can strain a bollock if you lift it on your own.

[Nickfromwales]

2 hours ago, Mr Punter said:

You can strain a bollock if you lift it on your own.

lol. Carted a few around and my bollocks are still in mint condition 

 

Most would have a +1 on these jobs.

[HighlandWoman]

6 hours ago, Nickfromwales said:

Go for 25mm plywood? These grab rails may have to prevent you from taking a tumble, so I’d have this done properly first as last.

 

If you tank the plywood then you can tile straight to it with a flexible, cementitious tile adhesive. Do NOT let anyone use ready mixed acrylic tile adhesive here, whatever you do!!! This stuff is crap, regardless of what promises are written on the side of the tubs.

Yep was planning on using proper adhesive. I had genuinely not thought of going up to 25mm but that seems like a good shout if I can get it up here.

5 hours ago, -rick- said:

 

I thought I'd read that 18mm was the standard for accessible (or convertable) bathrooms (attached to wall at 400mm centres IIRC).

I don't mind paying more, it does depend on whether I can actually get the right grade up here.

5 hours ago, Nickfromwales said:

If I was going to buy 18mm ply and then pay someone to fit 18mm ply, I’d at least want to consider going to 25mm and see if it was a much better, long term solution, than to find 18mm was just ‘ok’.

 

UK b regs is a “standard” it’s just a totally crap standard and the worst job you can do legally. Nothing to strive for!!

 

If a few more £10’s can make an ok job into a great one, and then that negates the plasterboard, then on paper it would be cheaper and better?

I will definitely see if I can get 25mm

3 hours ago, JohnMo said:

Our 12 degs roof is covered in the stuff, some off cuts have been sat outside for 5 years now. Not covered allowed to get wet. It's still in pretty good condition, considering.

was that marine ply or WBP?

3 hours ago, Nickfromwales said:

As always, you get what you pay for  

 

@HighlandWoman ask questions of the quality of the plywood, and get a good installer.

I'm installing it myself. A slower and probably over-engineered job but after deciding to pay trades to put in the en suite, I'm just not willing.

3 hours ago, Mr Punter said:

You can strain a bollock if you lift it on your own.

Fortunately I have none! I will be getting a strong man to hoik them up the stairs and help me though, whether it's 18mm or 25mm

 

 

Thank you everyone for the brilliant help and feedback. I'm going to go with ply and will try to get the 25mm. If I can only get 18mm I'll pack out between the studs in the general area.

[Nickfromwales]

You can ask the timber merchant to cut the 8x4 down to 4x4 to make it more manageable.

 

If you’re doing this yourself, you’ll have bigger balls than most!

 

Good luck, and make sure you search this place for plumbing tips etc, or just ask more questions and we’ll do our best to try and not let you feck it up.