Adhesive removal etc question

[alba2]

I am removing ceramic tiles from chipboard flooring in the bathroom, and it is proving quite difficult.
The tiles are really stuck down and only break out in small pieces.
How do you usually get tiles up?
The old adhesive is black and is leaving a residue behind. Any advice other than scraping to remove the adhesive?
Finally, I will be screwing and glueing 16 mm Hardie Board onto the existing chipboard. Will it be ok to cover the really hard to remove residue of the adhesive, with fresh adhesive?
Thanks

 

[Richard C]

Do it peoperly if you want it to last, the adhesive residue will not be flat & could give you all sorts of problems. Chipboard, even overboarded, is total crap in a bathroom, be brutal, rip the lot up & start again with 18-25mm WBP ply.

 

[alba2]

Thanks for taking the time to reply.
I was hoping you weren't going to say that!
I don't want to take out the toilet, and the waste pipe is boxed in the length of the room. It is nicely boxed in with rounded plastic edges.

I also wonder just how good external ply is once wet. Does it de-laminate? My reason for saying this is that someone on this site said that they coat the underside of the ply to protect it from moisture! If it is supposed to be resistant to water, why protect it against moisture?

 

[Richard C]

I also wonder just how good external ply is once wet. Does it de-laminate?

No it won’t de-laminate the adhesive used on the veneers is waterproof.

My reason for saying this is that someone on this site said that they coat the underside of the ply to protect it from moisture!

That would probably be Gcol, Tictic, Jefoss, me & probably a few others; & my appologies if I missed you out .

If it is supposed to be resistant to water, why protect it against moisture?

WBP’s water resistance is in the adhesive used to stick the veneers together, it’s still wood & if wood gets wet or is exposed to moisture it expands but it won't fall apart. The top face of a bathroom floor is covered in tiles so, effectively, not much moisture can get in there. The underside is covered with nothing & so if it isn’t sealed (SBR primer), can absorb ambient moisture or even water in the event of damp conditions or a flood. If the underside veneers absorb moisture, they will expand; if the top veneers don’t absorb any moisture the ply will warp (cup upwards) & there go your tiles. Also a common problem with real wood floors.

Any other lessons you would like

 

[alba2]

Thanks again.

From your explanation it would appear that external ply is not foolproof either!

I can't help but think that the ends of the ply should be sealed too.

We inherited the existing setup and curiously the ceramic tiles were laid directly onto chipboard. There has been some leakage of water at a corner over time, but no swelling of the chipboard, and the tiles are a b....r to remove, so really good adhesion.

 

[Richard C]

From your explanation it would appear that external ply is not foolproof either!

There are better if not somewhat more expensive options when over boarding but what else would you use for a replacement floor? Properly laid & fixed WBP ply is the best you will get & you should have no problems whatsoever but it's still wood & will become dimensionally unstable if it gets wet (you must tank it in a wet room) or the underrside/edges absorb moisture, hence the need to seal it.

I can't help but think that the ends of the ply should be sealed too.

Yes & the edges should be sealed too.

We inherited the existing setup and curiously the ceramic tiles were laid directly onto chipboard. There has been some leakage of water at a corner over time, but no swelling of the chipboard, and the tiles are a b....r to remove, so really good adhesion.

You’ve been lucky.

 

[alba2]

What would you recommend to seal the edges of 18mm marine ply>

Is it necessary to seal the underside? The marine ply shower base will be about 9cms above the concrete sub floor. The sub floor is the first floor of a building.

 

[Richard C]

What would you recommend to seal the edges of 18mm marine ply>

An SBR primer/sealer; & you really didn’t need to go to the expense of using marine ply.

Is it necessary to seal the underside? The marine ply shower base will be about 9cms above the concrete sub floor. The sub floor is the first floor of a building.

Yes, the distance makes no difference wherever it is; we are talking ambient moisture or accidental exposure to water here, not the proximity of your bathroom to the ground!

 

[alba2]

Many thanks for your advice.