Hi all, apologies in advance for the newbie question. I’m not in the trade, however we’re going through a renovation currently and we’re stuck between the builders and floor fitters for advice in terms of floor prep, I’ve done so much reading that my head hurts! We’ve had a anhydrite screed put down beginning of September with UFH which has been on for the 3 weeks, although I’ve switched it off a few days ago in preparation for the floor prep and install. Laitance were sanded off very early on and moisture levels currently seem to be between 0.5% and 0.6 % CM. I don’t pretend the numbers and I’m using a cheap Stanley moisture meter I picked up. It was primed using Stopgap P121, 1:1 mix for first coat, neat second coat, all finished yesterday evening, We are having a glue down engineered wood floor and the floor fitters arrived this morning and were a little concerned that some areas were still a bit tacky and we decided to leave it all for today, they may come back tomorrow. I was just looking for a bit of help in knowing if I’ve gone down the right route with all of this, so my questions were: Assuming screed is flat and level, is P121 sufficient as a primer for use for the polymer adhesive they are using? How long does P121 take to dry, is it tacky simply because we haven’t left it long enough, or is there a more fundamental issue with the moisture levels in the screed? Is there anything that I should be doing differently? Thanks in advance.
Yeah its crap!! I had some left over from a while ago and used it on my kitchen floor 2 weeks ago whilst our extension is being built and it's still tacky... You say it's been 3 weeks since your new anhydrite had been put down??
So is the approach essentially right, but you're saying P121 isn't great? What's the worst that can happen given that I've used P121?
You should of had a hygrometer reading. Or a carbide test. You don’t really know if it’s dry. I would of used a dpm instead
Do you know why some sources say that a DPM shouldn't be used with anhydrite with UFH? Or have I misunderstood that.
Not heard anyone bonding to a primer. Doesn’t sound a good idea really. As long as the floor was sanded / grinded correctly then having the heating on would help dry it but it would need a proper test. I’d then go with a the primer but a smoothing compound ontop of it before the wood.
Because the worry was using a dpm while there still a lot of moisture in the slab will weaken the surface and fail the dpm. I would suggest you force dry it and run the heating. Get it below 85% rh and then dpm with wakol ms330 or pu280 then bond to that with wakol ms260. As Daz says fball may not advise sticking engineered to their primer as a option
