What went wrong...?

[zoemac]

We hired BIG electric heaters and had them onsite for laying the screed. These we used for around 6 weeks after so I'd be surprised it if wasn't dry. It then had another week or so with the underfloor heating on low.

I should add that the Screed Firm thought that this would me sufficient.

 

[zoemac]

Yes - no test was carried out - I think we all just presumed after over 2 months it would be dry.

 

[zoemac]

How do I put pictures up on here?

 

[zoemac]

https://www.facebook.com/media/set/?set=a.10155145852350113.1073741834.644845112&type=1&l=398ee69809

 

[zoemac]

I've just set up a facebook album with some photos - hope it works. https://www.facebook.com/mcleanzoe/...41834.644845112&type=3&viewas=100000686899395

 

[Dave]

Just to add , if the SBR wasn't diluted to correct ratio , it would simply skin on the screed surface ... Also SBR can be used as a primer but it is advisable to use an acrylic primer and always dilute to particular brand recommendations .

as above the trend now is to use a gypsum based adhesive ....

also so when you turned on the heating , did you do it gradually or just cranked it on ..?

 

[zoemac]

I just lifted a tile again, and I have added some photos to the Facebook album (link above) the floor underneath feels a little damp despite the underfloor heating being on - is this normal, or is this a sign that the screed was not dry enough when it was tiled.

The adhesive is very firmly stuck to the tile, but not at all to the floor. The floor is covered with a white substance which is dusty in places and peels in others. I think this is the remains of the SBR.

Does the fact that I can peel/scrape off bits of SBR mean that it skinned rather than soaked in?

When I scrape away the SBR the floor underneath looks good and clean - no other sign of residue or laitance. It is rough to the touch so I would have thought it'd be an ideal surface to tile onto.

 

[Dash J]

I think laitance is the problem here
i have seen exactly the same problem on 150m2 of granite with ufh
the floor was not scrabbled,laitance removed
it was exactly as you say,wet underneath and no adhesion to sub floor
white patchy areas,chalky its laitance

 

[zoemac]

Thanks Dash. What would the laitance look like on the floor before tiling? Do you not think this could be the SBR skinning or a reaction between the gypsum floor and concrete based adhesive? When the floor was laid we were left with a shiny grey surface layer which as we walked on it cracked and flaked off. Brushing with a stiff brush removed the remainder leaving a clean surface which looked just like the surface between the powdery/peeling layer which is under the tiles now. Can you see the pictures?

 

[Dash J]

Hi Zoe I haven't seen the pics,will have a look
just with what you are saying it sounds v much like laitance
it's the word powdery that makes me think this
also not commissioning the ufh or checking the screed is dry is a major error
it sounds v much a lift and re lay unfortunately
I don't know who blame lies with because the screed needs to be checked for moisture
the tiler could blame you,you could blame the tiler or the builder