Tiling over cracked screed floor

[bill]

Hi all you experts,

I have a liquid screeded floor which has been down for over 12 months. It has underfloor heating under in the form of warm water piped.
There are now at least 18 largish cracks all about 1.5m randomly over the 5m x 7.5m area.

I'm told that it is okay to tile over these with large limestone flagstones.

To me the cracks resemble the tectonic plates and I'm curious to know whether people in the know would agree that its fine to carry on and tile.

Cheers

[Dave]

Hello Bill and welcome..

Which form of liquid screed is it.. cement or anhydrite etc..?

[Phil Hobson]

Hi Bill any pics?

[bill]

Hi Phil,

Got loads of pics but have attached just 2 for you to see that are representitive of all 18 others.
Really worried about these but need someone professional to either confirm or dismiss my thoughts

[bill]

Hi Dave,
This is a cement liquid screed as stated in the suppliers web details.

My very first time on a forum like this....... fells like you can get some good advice from professional people

[garythetiler]

hi Bill the way I see it you have 2 options option 1] epoxy stitch repair then fibre reinforced levelling compound option 2] epoxy stitch repair and ditra mat
I wouldnt tile the floor the way it is now with

[bill]

Hi Gary,

The screed supplier says this cracking is normal for a liquid screed floor. What do you think?


Thanks

[Phil Hobson]

Hi Bill, does the screed sound hollow (drumy) when you tap it? especialy around the cracks.

[bill]

Hi phil,

Not sure how I check this but I am almost certain the cracks are completely through the screed even with the polypropelene fibres they had in the the mix.
Really worried as the area in total is almost 95sq mtrs

[Phil Hobson]

I would be tempted to get the screed rep out to look at this, screed does shrink when curing, if it is solid and not hollow sounding then Gary's solution would work, but we are fortunate to have a valued member of this forum, who is the leading expert on screeds of all types (Ajax) Alan may pick up on this thread and give his advice, if not it might be worth giving him a PM

[bill]

Hi again phil,

Sounds dumb I know but how do I give him a PM....... Don't laugh i'm a novice

[Phil Hobson]

Hi Bill, not sure if you can send a PM Dave or Dan, or any Mod may help , you may have to get your post count up. If you look at forum leaders you will find Ajax, he is a trusted adviser, try and PM him by clicking on his profile the you will get the option to send him a private message. Hope this helps.

[Dave]

You can contact Alan (Ajax) here>>>> http://www.tilersforums.co.uk/privat...=newpm&u=12267

[Phil Hobson]

Thanks Dave. you explain it so much better than me

[Dave]

[bill]

Sometimes when things go wrong its very difficult to know what to do. Just wish I found this earlier.

The floor is diabolical but the supplier thinks he is a star.

This is a personal project on hold now for over a year because of a stand off with the liquid screed supplier

[Phil Hobson]

Bill between Dave and Alan, you are in very good hands

[bill]

Hi Phil,

Sound like you have a wealth of knowledge. Thanks for your help. Sent a PM to ajax through the link with a brief of the problem

[Phil Hobson]

Hope you get it sorted Bill, I'm sure you will. This forum is awesome, some top people on here

[Ajax123]

hi Bill the way I see it you have 2 options option 1] epoxy stitch repair then fibre reinforced levelling compound option 2] epoxy stitch repair and ditra mat
I wouldnt tile the floor the way it is now with

Go ditra, not levelling compound repair the cracks after the heating is commissioned.

[Ajax123]

This is very common with liquid cement based screeds. They crack but this should be controlled in the design phase by the inclusion of joints and bays. Typically 15m2 max bay size with aspect ratio no more than 2to 1and additional joints across door thresholds and between independent zones.

Who is the screed supplier. Or which product was it.

Resin stitch and ditra is the way to go. I have pm you back ill with a bit more info but if you need more help just ask.

This is not a disaster by any means but will need some work to sort it.

[jay]

Hi Bill, does the screed sound hollow (drumy) when you tap it? especialy around the cracks.

id say yes

[bill]

Hi Ajax,
Really appreciate your reply. Not sure what your specialist areas are but give you a basic outline on the events to date.

Floor was prepared to accept liquid screed over ufh (piped warm water)to cover 85m2 (2 rooms roughly35m2 each plus some small areas). Supplier turns up and does a quick visual check sets up his staff and laser level and starts pumping cementious liquid screed. Screed starts to set very quickly so he stops and adds loads of water. Starts to pump again and he finds it setting still. At this time we had 2.5m2 of setting sludge on the floor. He decides to try and spread it over the heating pipes with shovels. It was posssible to walk on at this stage and orders another lorry, pipes were full of setting liquid screed so had to be cleaned out. Then pumped the new screed on top of the old but could not get a finish because it was about 20mm thick and difficult to tamp down. Finish was rubbish so in the other room he made the floor height higher to it was easier to get a finish.

The floor has got loads of cracks now and have increased with time all of which are 1.5m or longer and through the section of the screed

[Ajax123]

Sounds like not much gone right on this one. The cracking could be associated with many things and usually a combination of several. These include excessive water, lack of curing, unstable substrate, over rapid dryingor setting. Was this a bagged product mixed and pumped on site or asit delivered in ready mix lorries?

My level of expertise is drawn from lots of experience and technical qualifications in screeding and concrete technology.I am currently working as technical and specifications manager for gyvlon working with calcium sulphate screeds.

[bill]

Hi Ajax,

Thanks for responding to my little problem?

Delivery to site was a ready mixed lorry.

Have you seen the pics I sent to Phil.

Supplier is deep in denial of any responsibility.

Thanks

[Ajax123]

When you say the supplier do you mean the screed installer or the ready mix producer.

[bill]

Both. The redy mixed supplier is also the installer.