I went to look at a job that has u/floor heating and the screed on top I have to say is pretty level (the guys on site said it was very liquid when poured) and has what appears to be quite a shiny surface. It has only been down a couple of weeks so the Tramex reading was off the scale but the vinyl (Luvanto) isn't going down for a while yet. I am trying to get information from the builder as to what the composition of the screed is but in the meantime does anyone know if there is a "standard" type of screed used over ufh and if so what the composition is? This is in case I need to screed the sub floor before installing the Luvanto.
Surely they can tell you what they used? They're bound to have receipts for the purchase if they can't remember. For UFH it'll have fibre in it....... Or should have!! If they've used standard screed it could crack when the heating is switched on. In fact, has the heating been switched on and commissioned yet? If not, when they do it should be switched on low and turned up slowly over a couple of days, turned back off and left off whilst fitting. Once the fitting is finished, the heating should be left off for a couple of days then turned on low and built up slowly.
If it's liquid cement it could be anhydrate. That shiny surface starts to come off after the builders start working on it! Get the number for the cement company?
id say the same as merit, very liquidy and shiney surface = anhydrite, youd need to be very very sure its dry then grind back the shiny surface then use acrylic primer and a calcium sulphate based smoothing compound to be safe, and with anhydrite you want to be safe, a company I do abit of work for, on one of their sites didnt find out what the slab was before going in and fitted a load of spacia they had 9 plots pop as they didnt do it properly, there cost to replace.
Be careful with anhydrate I had a job this year that was still saying wet after 6 months a core test was done along with a disclaimer before I laid the floor and its still down. This was engineered fully bonded. In your case you can't do a core test due to the ufh so be careful. You do have to grind the surface though.
Agreed sounds like anhydrite. Takes about 7 weeks to be dry enough. There's a company near me that's a major supplier, when they supply it they will do a moisture test after 7 weeks and pass it fit to tile or cover with vinyl, the stuff the supply doesn't need the surface ground off.
