20 to 40 mm screed, any recommendations ?

bertie 56

Hi everybody !

I have to make a screed that is 20 to 40 mm thick. I have already a uneven slab that is 130mm thick, with underfloor heating incorporate in.
Some guys came to do the job with primer and hydraulic binder but this has failed : the screed lifted and cracked . It is now removed and I'm looking at an alternative solution . 3 rooms has to be done flat, and one with a slight slope towards a floor trap .
A sand and cement screed doesn't seem to be the solution, because of the thickness, and the fact that I have a UFH in the slab seems to be a problem for the screed to stick .

Any recommendations about a product / serious company that could help ?
( I'm in Co Galway ).

Thanks

Dudda

bertie 56 wrote: »

Hi everybody !

I have to make a screed that is 20 to 40 mm thick. I have already a uneven slab that is 130mm thick, with underfloor heating incorporate in.
Some guys came to do the job with primer and hydraulic binder but this has failed : the screed lifted and cracked . It is now removed and I'm looking at an alternative solution . 3 rooms has to be done flat, and one with a slight slope towards a floor trap .
A sand and cement screed doesn't seem to be the solution, because of the thickness, and the fact that I have a UFH in the slab seems to be a problem for the screed to stick .

Any recommendations about a product / serious company that could help ?
( I'm in Co Galway ).

Thanks

I've specified Ardex for this a few times for similar situations but be warned it's expensive.

Johnnyhpipe

For future reference - min 75mm for sand/cement or it curls and shrinks excessively. For anything less you need to look at hemi-hydrate screed specialists. Plenty of reputable companies on a google search. Can't name them here of course.

bertie 56

Thanks for the answers.


I will look at Ardex products closely and try to find a company that knows good their stuff.
The previous team did use Ardex P51 as a primer, but with a different brand for the screed itself. I know they haven't put the primer and slurry correctly ( with few other mistakes too ) , but I think the problem was the poor workmanship more than the product itself.

Yes, I'll stay away from the classic sand and cement.
There is plenty of companies, but still have difficulties to find one for the job. On the 4 or 5 that came, only one accepted the first time.
The 20mm thickness did put them away...

Calahonda52

How did you arrive at 20mm, is this a DIY/U-tube/ pub bar mmat/self-build?

If the screed is non structural, then you may need to consider just enough to get floor level and adjust doors stairs etc

bertie 56

Calahonda52 wrote: »

How did you arrive at 20mm, is this a DIY/U-tube/ pub bar mmat/self-build?

If the screed is non structural, then you may need to consider just enough to get floor level and adjust doors stairs etc

Hi there,

The reason for the 20mm is :

I'll have some wooden floor on battens is some rooms, with a Finish Floor Level of 55mm above the actual slab.
What I need now is a screed of FFL 40mm for the rooms with tiles ( 12mm tiles + 3 mm glue).
All this in order to have the same FFL everywhere, not to have steps everywhere between tiled rooms and wooden floor rooms .

And 40mm of screed is the maximum, at the lowest point of the slab . But my slab is fairly uneven. In some places, I'm 20mm higher at the other corner of the room !

The screed is not structural, the slab underneath is plenty strong .
If I get the screed to stick to the slab and not crack, that's enough.
I can't go lower or higher than 20 to 40mm , door frames are done with walls plastered , and I won't get my level with the wooden floor in the other rooms...

Calahonda52

Okay, 3mm of "glue" under floor tiles sounds a bit light: are you tiling it your self?

bertie 56

Calahonda52 wrote: »

Okay, 3mm of "glue" under floor tiles sounds a bit light: are you tiling it your self?

Out of topic, but 3 mm of adhesive is the provider's recommandations.
They are small tiles, though, 100 x 100 mm.

In other rooms, they are bigger , 300 x 300 mm but are thinner too , 10 mm only.
According to the manufacturer, it's recommended to back-butter them with 2mm adhesive.
So, all together, I should reach 15mm of thickness with adhesive + tiles everywhere .

( and sorry for the " glue " mistake, I think everybody understood, English is not my mother tongue... )

Calahonda52

bertie 56 wrote: »

English is not my mother tongue... )

Just like the original Bertie.

ps am all done here