Considering Amtico Spacia over a newly poured 50mm gypsum natural screed. Waiting 8 weeks for screed to dry and will base it on testing of floor before fitting. The UFH is being set to high output as we already have a pump on our condenser boiler and fitting a second pump may be an issue. I need to find out max temp heating will reach as I’m pretty sure Amtico recommend heat up to 27’ max - is this correct? We are laying floor over gypsum in living room and existing tile in kitchen. Floor layer advised latex screed on tile (and on entire floor for uniformity). He also advised going ahead with latex screed in about 3/4 weeks as this can assist with taking moisture from gypsum floor, is this correct? also how long should planks be in the house to acclimatise?? Thanks all
Your floor layer advised you wrong, you shouldn't put a screed over the gypsum until it had been grinder to remove laitance and is dry enough. It's your choice with the kitchen, you can do it either way. If the floor is all over the place then I would say wait till its atleast screeded till you put your new kitchen in but if it's OK then kitchen can go in and screeded after.
Thanks. The guy who laid the gypsum told us it doesn’t need grinding as it’s a natural gypsum and its only the synthetic ones which need grinding??? We have easyscreed.ie
Should be using a gypsum levelling compound. It doesn’t make sense not to. Let it dry. Put down a dpm primer then gypsum levelling compound. Sent from my iPhone using Tapatalk
Naaaah merit, wickes own water mixed screed is more than up for the job. I'd be grinding it no matter what though, read the spec on it but I'd be waiting for the phonecall to tell me someone's tripped over a plank that's an inch off the floor
The one you add water to and m shake up in the plastic bag? Incredible invention. And builders still mess it up Sent from my iPhone using Tapatalk
Oh boy oh boy. Floor layer giving terrible advice, screeder giving terrible advice, you not understanding what you're doing.... it's a recipe for disaster. I take it you are in Ireland as you said easyscreed.ie Firstly, There is no such thing as a natural gypsum screed in the UK. All gypsum screeds in tge UK are made with synthetic gypsum, either anhydrite or alphahemihydrate.. I'm not even sure there is natural gypsum used in Europe either. ALL screeds should be mechanically abraded (sanded/lightly ground) to remove any loose material and contamination on the screed...it makes no difference if its gypsum or not. Sanding will also remove loose friable laitance. How is the screeder qualified go offer advice on prep for floor coverings. If you follow his advice which conflicts with industry advice is he going to pick up the bill if it goes wrong? I doubt it... Once sanded it needs thoroughly vacuuming. The underfloor heating MUST be properly commissioned and run before doing anything else. It then needs to be primed with a penetrating primer such as an acrylic or a water based epoxy. As for temperature it depends on who's screed it actually is. They vary. If it was Gypsol from LKAB then the delta T value would be around 8 which means the screed surface temperature will be around 8C lower than the flow temperature. If the flow temp us 35C the surface will be around 27C. This will drop a little with the addition of a smoothing compound (USE GYPSUM BASED NOT CEMENT BASED). So you will end up with a glue line temp around 24C. Most vynil adhesives require a maximum glue line temp of 27C but High Temp adhesives can go higher. You need temperature control on your UFH usually by means of a mixing valve supported by an emergency temperature shut off valve in case the boiler stat fails. Easyscreed.ie I think use hemihydrate which us less thermally conductive but they would have to confirm. I despair at the advice that is sometimes offered....
Oh and adding latex screed will inhibit drying NOT help it. If the screed is too wet the levelling compound will pop off the top.
