Suitable substrate to redo bathroom boxing-in?

[adamwilde]

Hello there.

We're having our bathroom redone along with some internal building work, and unfortunately we chose poorly when deciding who should do it. The builder (who is also a neighbour) made a poor job of the boxing-in for the back-to-wall WC and semi-countertop basin. And an even worse job of the tiling.

So, we're having the frame of the boxing-in reclad by a joiner and the tiling redone by another friend who is a tiler we've used very happily before.

The original builder used MDF for the boxing in, which concerned us (as did so many other thins along the way, but you live and learn). The joiner we're engaging to redo the boxing-in has suggested (and now purchased) moisture resistant MDF as an alternative substrate.

However, after he bought it I read somewhere that (a) it's not up to the job in this situation and (b) you can't tile onto it.
Our (new) tiler did some research and suggested Aquapanel from Wickes, but that's not suitable for loadbearing, and we're unsure about increasing the height of the boxing in with multiple substrates.

The boxing-in is at the opposite end of the bath to the shower, so should not be directly made wet, other than by splashing around the sink.

The joiner's due to do the work on Thursday, so any advice would be very gratefully received, as we're some weeks into this project now, and still feeling rather out of our depth.

Here are some pictures of the boxing-in as it stands, in case they're helpful:



Many thanks for your help.

[Dave]

Aquapanel is good for load bearing if it is the knauf one..or you could use hardibacker 500 12mm....but deffo not mdf..

[Colour Republic]

Why would it need to be load bearing, the studwork should be taking the strain. Or have I mis-understood your post?

[Diamond Pool Finishers]

same as DAVE,god that is some rough work, soze mate

[Colour Republic]

I would be tempted to bring that boxing out a bit further if you have the room, it doesn't look like you've got much clearance behind the basin, going to be a pain to clean and finish off nicely

[adamwilde]

Why would it need to be load bearing, the studwork should be taking the strain. Or have I mis-understood your post?

Forgive my ignorance: I figured it would partly be supporting the weight of the basin (?) and that it would need to support the weight of a person possibly leaning on the countertop while using the basin, but no one's going to be standing on it, so would the Wickes Aquapanel be sturdy enough for the job, do you think?

Otherwise, we should be able to get Hardibacker from a local supplier, I think.

[whitebeam]

Wickes if it's local, a good bit of framing for it as well

[adamwilde]

I would be tempted to bring that boxing out a bit further if you have the room, it doesn't look like you've got much clearance behind the basin, going to be a pain to clean and finish off nicely.

Thanks for your thoughts on this. I'm of the same mind, but we've precious little room in the bathroom (the door already hits the toilet as it is). Hmm. We might reconsider, though...

[Colour Republic]

Forgive my ignorance: I figured it would partly be supporting the weight of the basin (?) and that it would need to support the weight of a person possibly leaning on the countertop while using the basin, but no one's going to be standing on it, so would the Wickes Aquapanel be sturdy enough for the job, do you think?

Otherwise, we should be able to get Hardibacker from a local supplier, I think.

It's not ignorance at all, you are right in that some minimal weight would be supported by the covering but it should be just that - minimal. I'm sure when your joiner takes off the MDF he will be able to tell if there is enough framework to take any weight and insure there is no flex in whatever covering you decide. If not, it should be easy enough for him to strengthen it.

Was the framework a bit loose and wobbly when it was built and the builder told you the MDF would tie it all in and and strengthen it?

[adamwilde]

I don't think the framework was loose, but it sure wasn't square.

And this isn't even the worst of his work in there. By some margin. *sigh*

[Colour Republic]

I don't think the framework was loose, but it sure wasn't square.

And this isn't even the worst of his work in there. By some margin. *sigh*

Sorry to hear that

Can I ask what flooring you have down? If it's tile what did he tile onto?

By the way I’d be another vote for aquapanel. Also if possible I would get the tiler to tile under the basin (so the basin sits on top of the tiles) rather than up to it but that is just personal preference

[adamwilde]

I believe he put down ply before tiling the floor. he did use flexible adhesive for it. Then he drilled inaccurate 50mm holes for the 15mm towel rail pipes, which no pipe collars known to man will cover. Nice work indeed...

[whitebeam]

50mm holes could be classed as an over kill

[pjc]

over clad it with plaster board mdf would hold the wieght i would think if it was well screwed thats the cheapest option

[Colour Republic]

50mm!!! I hope you haven't got any small children that might get lost down there.

Ok last question I promise, Do you know what size ply he put down, how thick was it do you remember? You might be able to see at the door threshold if he hasn't covered it up

[adamwilde]

50mm!!! I hope you haven't got any small children that might get lost down there.

I know… It should be crime. I don't know if he and his plumber can't measure, or won't measure, or just didn't fancy it on the day. *shakes head sorrowfully*

Ok last question I promise, Do you know what size ply he put down, how thick was it do you remember? You might be able to see at the door threshold if he hasn't covered it up

Whatever it is, it looks to be about 5-6mm thick.

[jay]

hi i think you need to have a good look at what has been done its not good check your floor carefully before its to late if 6mm ply you will defo have a prob some jobs once done are best to start again and do propper good luck no quick fixes

[adamwilde]

What should the substrate for the floor be, please?

And, by the way, one of the tiles does creak a little.

[jay]

hi check your floor grout looking for cracks sighn of exes deflect depends on whats under ply and how much movement you have get your trusted tiler to go over job if neighbore has mucked it up with vanity area id say you will be constantly repairing the rest from pics it doesnt look good

[CON5933]

it looks like everybody's favourite on the floor...6mm ply
since you've already decided to put things right with the basin area, i'd suggest biting the bullet and get the tiler to re-do the floor..it sounds as if it's already failed (creaking tile?) which means the floor is flexing beneath it...
A good tiler would carry the right gear to drill the right sized holes for pipes etc...but they're not cheap, looks like the guy who done yours only had a 50mm tool, not sayin he's a bad guy or a cowboy...just not a tiler..
sorry you ended up in this situation, hope it gets sorted

[adamwilde]

Sorry to ask again, but if 6mm ply isn't up to the task, what should the substrate be? (It's going onto a first-floor wooden floor by the way.)

[jay]

depends on flex but min 12mm at the least you could ask for a tiler on here to have a look if you like

[ad tiling]

Thanks for your thoughts on this. I'm of the same mind, but we've precious little room in the bathroom (the door already hits the toilet as it is). Hmm. We might reconsider, though...

door hits the toilet i think building regs dont allow that
plumber will know the distance between door and
toilet

[Colour Republic]

Sorry to ask again, but if 6mm ply isn't up to the task, what should the substrate be? (It's going onto a first-floor wooden floor by the way.)

Get your tiler to look at it and give you his opinion on what would be best to use in your situation (would need to see more pics to give you info here), any flex in your floor will mean the tiles debond or maybe the grout cracks and water will find its way under the tiles. Felxible adhesive 'flex' to a certain degree but only a minimal amout, if the floor is bouncing it will fail.

Having looked at the photos again, is it possible to raise the boxing 20-30mm so it is level with the window reveal? giving you clearance all the way around the basin. Or would this mean the basin is at an unsuitable height?