Removing slate tiles and mortar from chipboard base

[U01krj]

Hello

I decided to replace my kitchen and floor and started work on saturday. I assumed that the slate foor tiles were laid onto ply on top the floor boards. Unfortunately the tiles have been laid straight on top of chipboard floor boards. So i have spent the past 2 days removing the tiles with hammer and chisel. The room is fairly large, circa 75 sq Metres.

So my problem is that there is lots of mortar stuck to the chipboard and am unssure if i should go the grinder / sander / sds with corret attachment or perhaps something else? The area is large so i have accepted it is not going to be quick. An engineered wood is being laid on top and my joiner says a 12mm ply will be good enough on top of the chipboard once the worst of the mortar has been taken off. Reading similar posts most seem to recommend replacing the whole floor, my joiner dismissed this... To clarify i am removing the current floor and he laying the new.

Any comments / thoughts appreciated. Apologies if this is a repeat of previous posts.

Cheers.

[getthewheelsinline]

Looks like a lot of work. Seeing as you plan to fit plywood anyway I would personally scrap the lot then just fit 18mm or 22mm plywood.

[Wes]

How well stuck is the adhesive?

What method of installation are you using to install the engineered wood i.e. floating (installed on top of an underlay), fully bonded (glued down), or secret nailed/screwed?

[U01krj]

Hi thanks for replies!

To clarify the plan is to ply on top of the chip without replacing then underlay then top flooring.

[mcluma]

Are you sure the door will still open

You will be raising the floor by quite a bit

[Wes]

If you remove the 'worst' of the mortar, that suggests you'll be leaving some down. This may create small voids under the ply. Which may either leave the ply bouncy or with humps once it's been fixed. Either or both of these will potentially result in movement of the floor when walked on, resulting in creaking etc. If your installer is intending on fixing the ply with screws at the correct centers - and enough of the adhesive has been removed - you may be okay. However, make sure he address any undulations or voids in the ply prior to installing the underlay.

If we're talking about leaving mortar residue, you may as well go the whole hog and grind the mortar off completely and float the floor straight over the chipboard (which as mcluma rightly points out, will prevent the additional height rise) . The ply option sounds like an easy fix to avoid removing the adhesive, but it likely won't be a good fix. 12 mm ply has flex. Additionally - If the idea of the ply is to avoid the dust creation when removing the mortar, there are solutions for that, in the form of dust extraction hoods. Although, there will always be some dust created.

If the mortar is well stuck, you could go down the skim coat route with something like Arditex NA and float the engineered straight over that. Which is also an easy fix option, but will likely provide a better result.

Installing 12 mm ply to solve a tile adhesive issue just doesn't ring right for me, especially for a floating floor. Unless, the idea with the ply was to address other issues i.e. shoring up the chipboard (even then, I'd personally want all that adhesive up). If the flooring was getting fully fixed, then ply would certainly be coming into the equation.

[Rorschach]

Looking at the skirting at the moment and then thinking ply (plus underlay) plus floor, I can see this being awfully thick. Considering the work involved removing the mortar and the mess I would just have it up and start again. Another factor to consider is that if the mortar was laid directly onto the chipboard the moisture may have already weakened and damaged the chip board underneath, the mortar may actually be holding the top surface together.

[mcluma]

Having looked at your last picture with the door!

Humor us here, could you measure what height there between the bottom of the open door and the "cleaned" floor

[U01krj]

hi

thanks for the posts! i guess whole point of these forums is to read/offer different opinions so contributions very welcome.

the height from clean floor to bottom of door is 31mm. there is the space there for 12mm ply + 5mm underlay + 8mm flooring. However, that is just there and as you can see i will need to make sure it is like that across the whole floor. the skirts are coming off before the new floor goes down.

The idea of ripping up the floor has been mentioned by quite a few people and others have said that is not the way. One question i have is, if ripping up the floor, what does one do for the edges? i.e. ripping up the floor would surely impact the walls, damage skirting etc so assume you stop short of the edges? so is that a mechanical saw that would create a nice edge to lay nice shiny new floor boards against?

The purpose of the ply was for something smoother to put a new floor down on, to flatten out any overly stubborn mortar and to shore up any damage created during the process of taking up the floor.

cheers

[Wes]

The idea of ripping up the floor has been mentioned by quite a few people and others have said that is not the way. One question i have is, if ripping up the floor, what does one do for the edges? i.e. ripping up the floor would surely impact the walls, damage skirting etc so assume you stop short of the edges? so is that a mechanical saw that would create a nice edge to lay nice shiny new floor boards against?

If you decide to remove the current floor, you could remove the skirting prior to avoid damage. At solid walls the chipboard will stop. At dividing stud walls, the chipboard would require cutting with the use of a circular saw (as close to the wall as possible). This may leave poor support for the dividing wall (depending on the direction of the joists - your builder will be able to advise on that), therefore, support will need to be added in the form of noggins and preferably hangers.

Then once removed, you would install minimum 18 mm T & G ply or new chipboard (although, chipboard is rubbish). You may need to add additional support where the old chipboard was cut. Again, your builder should take care of that if need be.

[mcluma]

Have you already started to take the adhesive off?

If so how long did it take you to do 1m2, and is it clean, so clean you can put new ply on it, and be happy with it, that when you are putting you're new expensive floor on it, you have no second thoughts about it,

Now how long did it took you for 1 m2, ripping up the floor and putting down a new one, will only take you a day at the most, and then you can, if you want, go for 25mm ply

[U01krj]

Hey

.... So i got myself one of those breaker tools with a bolster (??) attachment. 10 sq cms later i gave up. Spoke to joiner and we are now taking up the floor. Convinced him that it would take 7+ days to grind/remove mortar alone so makes sense.

Tks for feedback. Fingers crossed for the weekend!!

[mcluma]

Hey

.... So i got myself one of those breaker tools with a bolster (??) attachment. 10 sq cms later i gave up. Spoke to joiner and we are now taking up the floor. Convinced him that it would take 7+ days to grind/remove mortar alone so makes sense.

Tks for feedback. Fingers crossed for the weekend!!

sorry to the world of DIY. It takes a man to know when he is defeated - in the mean time, have a go at your skirting boards.

also know where you're time is best spend. if the skirting is nailed to the wall and you do not want to take the plaster of the wall (when you take the boards down. use a flexible hacksaw blade to cut down the nails - safe as much as possible of you're wall. you do not want to re-plaster the walls - this also works if the screws do not want to come out

Good luck and keep us posted

[U01krj]

floor finally down.... !!!