Self levelling

cosmowillie53

I have a rather uneven old concrete floor which I would like to level out.
Has anyone here used self levelling compound and is it easy to use for an average diy chap.
Thanks.

AthenaFlooring

Hi cosmowillie53, if you are going to do a DIY self levelling compound go for a bag and and bottle option. That way the mixture ratio will be 100% correct. And lastly read the instructions on whatever screed levelling compound you go for and ensure you have the correct laying conditions before proceeding!! Preparation is key!

King Mallie

You need to apply poly bond to the floor before the compound. Then make sure you have a mixer drill to mix compound. Tile shop have some excellent levelling compound. No need to anything except add water as per spec.

AthenaFlooring

No need for poly bond if ardex na is used! Primer and screed in one!

King Mallie

better safe than sorry to use poly bond for the sake of a few euro

cosmowillie53

Thanks for the replies so far .
I noticed a couple of spots around the floor that appear damp(ish). I also noted that these only appear when it has been damp outside even though this floor is in the center of the house...it is an old house.
Should I use something like tanking slurry on the floor and then levelling compound. I am having the walls plastered as well so should the floor be the last thing to do.
Thanks.

Wigster

All, i have a bathroom that i put latex self levelling compound. However there are lots of hair line cracks on it . Before the job I removerd the osb boards and replaced with ply. Put on a coat of pva. There is heating mat on it which is stapled to the ply, I then put another coat of pva before pouring. The compound is just 6 mm as per manufacture. The floor is not crumbling or parting but i can see slight deflection when pressure applied. Is it ok to tile on or will it cause me issues?

AckwelFoley

Wigster wrote: »

All, i have a bathroom that i put latex self levelling compound. However there are lots of hair line cracks on it . Before the job I removerd the osb boards and replaced with ply. Put on a coat of pva. There is heating mat on it which is stapled to the ply, I then put another coat of pva before pouring. The compound is just 6 mm as per manufacture. The floor is not crumbling or parting but i can see slight deflection when pressure applied. Is it ok to tile on or will it cause me issues?

You need zero movement
I suspect you haven't heavy enough ply on the floor. If under the ply was the joists and you put 1 sheet of ply 18mm that's not enough. I don't care what anyone recommends, you'll need two layers. Ive always done this when building the house and never had problems. Ive come across the problem and its generally down to that. The ply needs to be layed cross ways on each other.

Also. . I hope you watered down the pva. Neat pva is the root of many problems. Neat pva glazes to a shiny surface that doesn't soak into the surface as its required to

Wigster

AckwelFoley wrote: »

You need zero movement
I suspect you haven't heavy enough ply on the floor. If under the ply was the joists and you put 1 sheet of ply 18mm that's not enough. I don't care what anyone recommends, you'll need two layers. Ive always done this when building the house and never had problems. Ive come across the problem and its generally down to that. The ply needs to be layed cross ways on each other.

Also. . I hope you watered down the pva. Neat pva is the root of many problems. Neat pva glazes to a shiny surface that doesn't soak into the surface as its required to

Yes i think your right that its the sub floor thats the problem. The pva was was watered down. The compound is not loose as i suspect it has bonded well to the heating mat. I cannot now remove due to mat. Would it be safer to put down another layer of compound before tile adhesive or could I go to tile adhesive now? Will tile grout lines crack due to deflection which ever method?

AckwelFoley

Wigster wrote: »

Yes i think your right that its the sub floor thats the problem. The pva was was watered down. The compound is not loose as i suspect it has bonded well to the heating mat. I cannot now remove due to mat. Would it be safer to put down another layer of compound before tile adhesive or could I go to tile adhesive now? Will tile grout lines crack due to deflection which ever method?

Its quite likely that the grout will crack out in time because the floor is deflecting. I think its a waste of time adding more floor levelling on it. Its not going to stabilise it in the way it needs to be. Best chance you have is with a bigger tile, it will displace the weight over a larger area...fingers crossed after that, otherwise you you will need to start againand add more ply and screw down heavily

Wigster

Prior to laying the ply I did put extra bridges into between the joists and screwed it very heavily. Thinking back since I put in the screed I remember looking into the room and cracks had appeared before I even stood on the floor. I wonder if some of the water evaporated also. I will tile with a larger tile and see how I go thanks.

Safehands

cosmowillie53 wrote: »

Thanks for the replies so far .
I noticed a couple of spots around the floor that appear damp(ish). I also noted that these only appear when it has been damp outside even though this floor is in the center of the house...it is an old house.
Should I use something like tanking slurry on the floor and then levelling compound. I am having the walls plastered as well so should the floor be the last thing to do.
Thanks.

I recommend an epoxy DPM. If damp is visible then it may require two coats. Try to get a moisture reading done. The self leveller can be applied on top of the DPM, but if you intend to leave some time between applying the epoxy and the leveller, then a third coat, blinded with sand may be an option you should consider. The choice of Self leveller really depends on the thickness you intend to apply. The "normally" available ones go to about 6mm, others can go as thick as 15 or 20mm. Under no circumstances should you apply a self levelling compound on a damp floor. PVA can be used to bond one of these screeds, but not in a damp environment. PVA's are no good with damp.