Replacing chipboard floor for tiling advise

[tony Dimartino]

Im about to rip up a chipboard floor which is falling apart, I was going to lay ply and overboard with NMP or Hardie, Ive seen that there is 22mm backing board can this be used directly on to joists or does am i better laying ply and then a 6mm backing board? Any adivise appreciated

also one of my stud walls needs reboarding and is part of a shower, should i use 12mm NMP straight on to the metal studs and does this need tanking?

many Thanks

 

[Boggs]

I would replace the floor with new chipboard, then overlay with 6mm Hardie Backer stuck to the chipboard and screwed at 150mm centres.
The 150mm is my preference.

When removing complete floors just be mindfull of the wall that goes the same way as the joists, if there is not a joist underneath the wall make sure you only take back the existing floor to the nearest joist in the room, otherwise the wall will have nothing holding it up and may start to drop over time.

I would not bother with Hardie Backer on the walls, use 12.5mm moisture resistant plasterboard and tank or buy Wedi or Delta etc boards.

 

[Old Mod]

Ive seen that there is 22mm backing board can this be used directly on to joists

22mm NMP or another product called GIFA board can both be fitted direct to joist and are structural materials.
Where possible I’d always substitute any type of timber or particle board flooring for these products.
They’re inert materials and are unaffected by moisture and temperature change.
And also keep build up to a minimum.
But that’s my personal preference.

And as above, wedi style sboards on walls.
Although personally I find metal suds can be a little flimsy depending on the stud centres.
I’d be concerned that a single skin 12.5 wedi board straight to metal stud would not be stable enough.
Personally I like metal studwork to be double skinned.
As long as the outer skin is waterproofed/tanked correctly, the inner board could be pretty much whatever you want.
It’s the double layer that provides the strength.

Not disagreeing with Boggs at all, I’d just take a different approach maybe, depending on circumstances.

 

[Waluigi]

Over in Germany that’s exactly how they deal with metal stud work. They double board it.

Regarding the floor, I would use a decent quality ply wood (18mm) exterior grade. Wickes sell it. And then glue and screw HB onto this. Then tape the joints.

 

[Boggs]

Oops, might have confused him now!

 

[tony Dimartino]

22mm NMP or another product called GIFA board can both be fitted direct to joist and are structural materials.
Where possible I’d always substitute any type of timber or particle board flooring for these products.
They’re inert materials and are unaffected by moisture and temperature change.
And also keep build up to a minimum.
But that’s my personal preference.

And as above, wedi style sboards on walls.
Although personally I find metal suds can be a little flimsy depending on the stud centres.
I’d be concerned that a single skin 12.5 wedi board straight to metal stud would not be stable enough.
Personally I like metal studwork to be double skinned.
As long as the outer skin is waterproofed/tanked correctly, the inner board could be pretty much whatever you want.
It’s the double layer that provides the strength.

Not disagreeing with Boggs at all, I’d just take a different approach maybe, depending on circumstances.

Thanks for your reply, one of the walls the plasterboard is completly off, would i be better adding more noggins? or using a 20mm marmox board instead?

 

[Old Mod]

Depends on it’s construction really. You just want it to be solid and deflection free.
If you can push boards in, it needs more support. The more solid it is, the more suitable it is for Tiling.
If there’s too much movement in the structure. It will fail.

 

[Waluigi]

which tiles are you using for your walls? Size and material.

 

[tony Dimartino]

which tiles are you using for your walls? Size and material.

Hi im going to be using 600x300mm 9mm porcelain tiles, on the wall, Im really confused on the best way to go. Have a look at the pics this is were the shower is going, do u think no more ply 12mm boards would be stronger than using 20mm marmox?

 

[Boggs]

The walls will definitely need some more uprights.
From experience I can say 12mm Hardi on metal stud work won’t go anywhere in a hurry!
But the walls I worked on were 450 centres if I recall.

 

[tony Dimartino]

The walls will definitely need some more uprights.
From experience I can say 12mm Hardi on metal stud work won’t go anywhere in a hurry!
But the walls I worked on were 450 centres if I recall.

Yes I was surprised on how little supports there, I'm going to reinforce but still can't make my mind up to go nmp or marmox

 

[Old Mod]

Regarding the floor, I would use a decent quality ply wood (18mm) exterior grade. Wickes sell it. And then glue and screw HB onto this. Then tape the joints.

We spend our lives advising against using materials that expand and contract with atmospheric conditions or copious amounts of water, British Standards have just been amended the guidelines to eliminate ply walls , and floors are just a matter of time.
So why do we still want to fit ply and then overboard it!
That’s two processes, good quality ply (contradiction in terms) barely exists, and marine ply although the correct material is extremely rarely used.
And then you want to do it all over again by overboarding with a cement board that needs glueing, screwing and the joints taping.
And that is NO guarantee that movement cracks won’t transfer thro. It happens all too regularly.
Any gypsum structural board goes straight to joist, is primed and then tiled and has a lower profile overall.
I’m not digging you out in particular Andy (waluigi) cos it’s said all the time.
I just struggle to understand the logic behind it.
And as far as existing boards going beneath stud walls are concerned, most plunge saws will cut within 15mm of a wall, so I don’t teally see that as an excuse either.
If you’re gonna strip everything back and start again, why put the same bloody stuff back again.
It really doesn’t make sense to me.
And breath.......

 

[Old Mod]

Yes I was surprised on how little supports there, I'm going to reinforce but still can't make my mind up to go nmp or marmox

Marmox, Dukka, wedi, anything like that is a better surface than nmp.
And they only need tanking on the transitions.
(Wall to wall and wall to floor junctions) and over the mechanical fixings (screws and washers)
NMP needs tanking in its entirety.

 

[Old Mod]

Omg! I hadn’t seen photo, been too busy ranting!

That needs work for sure.

Like Boggs says, needs more stud work haha

Doesn’t matter what you clad it in, it needs more studs.

 

[Waluigi]

We spend our lives advising against using materials that expand and contract with atmospheric conditions or copious amounts of water, British Standards have just been amended the guidelines to eliminate ply walls , and floors are just a matter of time.
So why do we still want to fit ply and then overboard it!
That’s two processes, good quality ply (contradiction in terms) barely exists, and marine ply although the correct material is extremely rarely used.
And then you want to do it all over again by overboarding with a cement board that needs glueing, screwing and the joints taping.
And that is NO guarantee that movement cracks won’t transfer thro. It happens all too regularly.
Any gypsum structural board goes straight to joist, is primed and then tiled and has a lower profile overall.
I’m not digging you out in particular Andy (waluigi) cos it’s said all the time.
I just struggle to understand the logic behind it.
And as far as existing boards going beneath stud walls are concerned, most plunge saws will cut within 15mm of a wall, so I don’t teally see that as an excuse either.
If you’re gonna strip everything back and start again, why put the same bloody stuff back again.
It really doesn’t make sense to me.
And breath.......

Not digging me out yet you ignored Boggs’ reply suggesting chipboard is laid first and then overborded.

Why would I lay ply and overboard it? Because that’s something I’ve done before many tines and very rarely see 22mm cement boards. Maybe I’ll look into this further. Thanks for the information.

Also Boggs suggested that there might not be a joist under the stud wall if the joists run parallel with Said wall. That has nothing to do with cutting up to the stud wall. My apologies if I misunderstood why you mentioned that.

 

[Old Mod]

Not digging me out yet you ignored Boggs’ reply suggesting chipboard is laid first and then overborded.

Why would I lay ply and overboard it? Because that’s something I’ve done before many tines and very rarely see 22mm cement boards. Maybe I’ll look into this further. Thanks for the information.

Also Boggs suggested that there might not be a joist under the stud wall if the joists run parallel with Said wall. That has nothing to do with cutting up to the stud wall. My apologies if I misunderstood why you mentioned that.

Haha Andy, honestly I was not ranting at you, you have my word.
I expect the first comment got me brooding about it.
I don’t publically berate members. (Often ) I do it in private.
I was just being a bit expressive about my feelings on the subject.
I truly apologise if you felt I was being personal, I wasn’t.
And anyway if I was digging you out, I’d of said so.

Believe me there are many guys here that would do exactly the same as you, it just baffles me as to why.
It’s a shame you can’t get hardiefloor anymore, brilliant product.
Sorry Andy.

 

[Waluigi]

It does raise an interesting point though and honestly not something I had considered.

I bet if we fast forward ten years someone might be ranted at for rebuilding a room yet not replacing the timber joists with the new cement resin joists that would be available in 2028....

 

[tony Dimartino]

It does raise an interesting point though and honestly not something I had considered.

I bet if we fast forward ten years someone might be ranted at for rebuilding a room yet not replacing the timber joists with the new cement resin joists that would be available in 2028....

I totally agree, I last tiled 12 years ago anfdthen I put ply down sealed it and tiled, TBF it never cracked or moved in 12 years. But things have come on so much its a complete minefield !!!

 

[Perfect Tiling]

One thing you will need to be aware of is the weight of your tiles. No matter how many studs and dwangs you put into the wall if you go down the plasterboard route it will only take a maximum weight of 32kg.....thats for everything. Allow around 4kg for cement adhesive which you'll need as they're porcelain and that leaves 28kg for your tiles. I carry a set of bathroom scales as some of these tiles are so damn heavy. Topps regent 9mm tiles are right on the limit at 27kg a box of 6 (1.08 sq mtrs). 12mm HB 0r Marmox style boards will take well in excess of this.

 

[Boggs]

Not digging me out yet you ignored Boggs’ reply suggesting chipboard is laid first and then overborded.

Why would I lay ply and overboard it? Because that’s something I’ve done before many tines and very rarely see 22mm cement boards. Maybe I’ll look into this further. Thanks for the information.

Also Boggs suggested that there might not be a joist under the stud wall if the joists run parallel with Said wall. That has nothing to do with cutting up to the stud wall. My apologies if I misunderstood why you mentioned that.

Using 6mm Hardie over new chipboard is what I would usually do, never had a problem but we all do things differently.

When I do a job I take into consideration how and what damage it might cause when it has to be removed.
22mm t&g No More Ply screwed directly to the joists is a great idea in theory but what damage might it do to joists when it has to be ripped up?
Floors are easy to replace, joists not so.

Joists under walls is a point I make from experience, if everyone cuts back the floors to the nearest 15mm without a joist under to support it the wall may well start to drop with the weight of tiles etc on it. It’s better to cut to the nearest joist inside the bathroom.

 

[Waluigi]

I’ve experienced it many times, Boggs.

In fact, I have taken up many a bedroom carpet to install timber between the joists so that I can take the whole floor up. Amazing how many builders ignore using a double joist under a stud wall in preference of no joist at all.

I still don’t see using ply/chipboard and then over-boarding as wrong necessarily but I do take 3falls point and shall be looking into this method further.

 

[Dumbo]

Using 6mm Hardie over new chipboard is what I would usually do, never had a problem but we all do things differently.

When I do a job I take into consideration how and what damage it might cause when it has to be removed.
22mm t&g No More Ply screwed directly to the joists is a great idea in theory but what damage might it do to joists when it has to be ripped up?
Floors are easy to replace, joists not so.

Joists under walls is a point I make from experience, if everyone cuts back the floors to the nearest 15mm without a joist under to support it the wall may well start to drop with the weight of tiles etc on it. It’s better to cut to the nearest joist inside the bathroom.

I worry more about floor sagging with no support next to walls . Also I don't make jobs to come apart .