Is this sand/cement backing???

[thedman]

Hi folks,

I've been planning my bathroom for about a month now, and feel quite prepared on what I need to do. I started today, taking the old tiles off the wall, they pulled off the plaster skim the were stuck to which I expected, but what is that the skim was stuck to. I've read that sand/cement is good to tile on to. I have a house built in 1976. Cavity walls, all the internal walls are concrete block. Is this sand/cement????

 

[thedman]

Sorry having probe attaching image.....

 

[thedman]

Obviously that's skim on there too, just wanted to give some sort of reference....

Clues:

1. Its a bit dusty, but would hoover to not very dusty.
2. Its pretty much rock hard.

Thanks in advance,

Dave.

 

[Gazzer]

Nope thats plaster, not suitable to tile to

 

[Diamond Pool Finishers]

i would say that is sand and cement ,skimmed with surafite /or thisal plaster, so if you remove the skim coat completely you will have a good sub straight to tile to if it is not dusty , you may need to prime it

 

[White Room]

My first thought was browning but looking closely it could be sand/cement, there are small stone as a sharp sand....

 

[Diamond Pool Finishers]

yes deffo S & C ,it has been poorly scratched with the devil float so it has offered no mechanical key for the skim to attach hence it coming away as seen

 

[Diamond Pool Finishers]

1976 it's what we would have used, it had probably been plasticised with FAIRY WASHING -UP LIQUED LOL

 

[The Legend; Phil Hobson RIP]

Hard to call from pic, I would try to score to surface with a sharp chisel, if you can make a groove in it then probably plaster, if not then sand and cement render. Just worth a go imo.

 

[thedman]

Thanks for all your replies. General opinion is s/c.

Here's two more pics,

one showing small stones:

View attachment 42339 yeah its blurry, but the stones are definitely stones...

and another showing the results of Phil's test, I scored it with the edge of a flat screwdriver:

View attachment 42340 Dunno how much that is worth.... as i applied enough force to scratch it. If it had been harder I would have applied more force so as to scratch it....

 

[Diamond Pool Finishers]

sorry mate i can't see the pic's ? it could be a weak mix of S & C and that would scratch as well !

 

[Gazzer]

Yes those 2 pics look more like sand and cement.

 

[thedman]

Try this:
and

 

[Aston]

hi diamond dave,
washing up liquid, that brings back memories. a cheap alternative to FEB mix ...happy days hey, it worked lol

back to the thread..very difficult to tell from the pics but it looks like thistle browning to me.

 

[Diamond Pool Finishers]

yes deffo S& C just scrape off all the skim and you will have the perfect substraight !

 

[White Room]

I would stabilize with a 3-1 sbr or 4-1, with the minimal looking devil floating out it could be a weak s/c mix....

 

[thedman]

I will do exactly that then.

Its going to be above a shower over bath, should I stabilize with a 3-1 sbr or 4-1 then tank with WP1, then use singlepart flexible as addy. Do I need flexible grout?? and how long do I leave the SBR for??

Thanks whitebeam.

Dave.

 

[thedman]

Thanks everyone to be honest...

Especially Diamond Pool Finishers who seems most adamant its s/c ---- I'm in agreement.

15 years ago I got a degree in Chemistry, one module - 10 weeks, was cement, 10 flipping weeks of cement, damn it seemed boring then. Wish I had paid attention!!!

 

[White Room]

My preference would be a 4-1 so it soaks in to s/c to stabilize, if your going to use WP1 I would use some of the powdered adhesive to flatten out the old s/c with the flat part of your trowel.

where your going to use the tanking...just a really tight coat and leave to dry otherwise you will be using a lot of tanking material on the rough surface.

Prime with the manufacturers acrylic primer and then apply your tanking.

 

[thedman]

Thanks a million. i really appreciate it.

 

[widler]

Defo sand cement,do as whitebeam and diamond say.
1976 a bit before my time but in 86 we still used sand cement, with fairy


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