Old Grout not shifting - Thoughts & Opinions

[pie1978]

Hi guys, thought I'd sign up here and seek some professional advise.

Moved house not long ago and now working my round the house removing traces of the previous owner's questionable taste!

I'm onto doing the bathroom now - plan is to replace the toilet, sink and tiled floors. Bath to remain (for now).
I've removed as much tiles as I can so the sink and toilet are still functional. Problem now seems to be removing the grout / adhesive from the back of the old tiles from the floorboards. Some of it has come up but there are sections that are absolutely refusing to budge - have tried a chisel, scrapers, a Bosch PFM 180E tool and I'm getting nowhere fast.

Thickness of the old grout varies from 1mm to 3mm at the worst parts but I could probably reduce this down to between 1 and 2mm.

I have 600 x 600 x 9thk Porcelain tiles which I plan to lay down.

Floor area to be covered isn't spectacularly huge either, only 1500 x 1700.

Question I have is would I get away with fixing 6mm plyboard over the floorboards and the existing grout / adhesive then laying the 600mm tiles on top or would there likely be too much flex and movement?

This existing grout / adhesive really is a pain to shift and the only other option I can think of (which is a bit extreme) is to remove the existing floorboards completely and starting from scratch.

Your thoughts and opinions much appreciated.

Pie

 

[pie1978]

General view of the bathroom



Typical view of what I'm up against (this has approx 3mm lip at the worst part)

 

[Bubblecraft]

Hi & welcome to TF. There are a few options. You could use a drill will an SDS chisel bit or a long handled heavy duty scraper like a Mutt. These options are free but involve some elbow grease.

This option comes at a cost but is far quicker & will give you a perfect substrate to tile on. You could put down a 6mm or 10mm (depending how bad the floor is) Hardibacker board using a single part flexible adhesive (SPF) & also screwed. The adhesive will take the imperfections out your floor.

If your substrate was concrete, you would also have the option of a self levelling compound.

No matter what method you go with, your floor will require re-sheeting prior to tiling so I would opt for option 2, Hardibacker. I would not advise over sheeting with plywood as there are so many things that can go wrong plus it takes a lot longer to fit than Hardibacker boards. Plywood also requires the underside & edges to be primed with an SBR.

Go the hardi route & I can guarantee, your floor will outlive us all

 

[Bubblecraft]

After looking at your pics again I see its P4 chipboard flooring & not floor boards. Either way, it will require re-sheeting but will be very quick to get the old sheets up & re-sheet.

If height is going to be an issue at all, you could remove your P4 & replace with 18mm marine ply. Just mind & coat the underside & edges with an SBR before fixing down. You could tile straight on to this which would give you a running height from hallway/adjacent room etc