Discuss Anhydrite laitence removal in the Canada area at TilersForums. The USA and UK Tiling Forum (Also now Aus, Canada, ROI, and more)
Yes it's that damned gypsum screed!
The builder assured me it's been sanded & laitence removed all bar one room. I'm on site today and they've got a guy using an electric hand sander with 80 grit paper. I don't think that's manly enough, how can I tell if the laitence has been taken down sufficiently?
Thanks in advance
You should be able to see and feel it is different in texture & colour. How long has it been down? Has UFH (if fitted) been correctly commissioned?
I had to try and remove laitance from a screed which had been down and commissioned for some 8 months. Was a nightmare I tell you!
It does have wet UFH and has been commissioned correctly, the floor has been down for around 16 -17 weeks. Ive had a little scratch at it & i have to admit I can't really tell!
You will struggle to get the laitance off with a hand sander after this amount of time. Laitance should really be removed much sooner...... around a week or so after pouring depending in drying conditions, thickness etc. Any pics?
In the shadowed one is how the majority ofnthe floor looks, in the other you can see a small lighter patch where i had scratch at it with a key.
Hope this is helpful
In the shadowed one is how the majority ofnthe floor looks, in the other you can see a small lighter patch where i had scratch at it with a key.
Hope this is helpful
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You really need a floor grinder ! I bought an errut PRM twin disc grinder that takes 6 no carburundom blocks you will need to go over whole floor up to edge as close as you can ! Basically it looks like it's power floated and when you get laitance off it looks more like screed ! You can hire grinders at hire centres mine is quite easy to use and fairly gentle some of the single disc ones are a bit aggressive and can dig divots in the screed ! Also may be an idea to get the screed company to send the rep out to do a carbon bomb test to check RH is low enough ! I've spent a lot of times exploring this animal lol worth the time though ! Good luck Dave
That to me looks like it needs sanding, and I don't think anything other than diamond disk will do it
Have you done some moisture tests ?
Thanks for the replies, I've had someone out to inspect it, an old school friend in the flooring industry, who confirmed it needs sanding properly with a heavy duty copper teeth wheel or suchlike!
So that's happening later this week & get a day or 2 of not looking at tiles!
What about the moisture ?
The UFH has already been commissioned, the guy that came to remove the laitence also checked the moisture with a couple of devices. He's a commercial flooring contractor & deals with these screeds all the time so I trust him.
Id want to know the actual readings, rather than trust an old school friend, who might not know the requirements for tiling
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