Hey everyone, I've done a lot of reading here and you seem a really knowledgeable bunch. Was hoping I may be able to get some advice. I'm trying to sort out a conservatory. It used to have a laminate floor which to be honest, was an embarrassment in how it had been left. I'm talking inch wide pieces on one side to finish it off which were loose. I ripped this up to find a ceramic tiled floor underneath, with a cement slab under that. Unfortunately, this was also a shocker of a job. between the high and low spot there was a difference of 52mm. Granted this was at opposite ends of the room, which is 5.1m long. But still, the levels are all over the place. I think either the concrete slab below it was just a really poor job with levelling or its dropped because they've not done the foundation properly. Either way, it needs fixing. I've taken the tiles off one side to reduce the high spot. Then used these tiles (approx 9mm thick if that matters) to tile on the low spot to bring the level up a bit. My plan was to put some levelling compound over it as its too thin to do another screed. Biggest variance is probably 15mm though may have some tiny divots in the slab where its 20mm. Vast majority will be around the 5mm mark I think. What would you use to level over it? Wary of using 1-10mm compound but given most of it will be pretty thin that seems the best option? We've been using water to minimise the dust and in my reading on this forum I noticed you need to be careful of moisture with levelling compound. Does that mean I need to let it properly dry out? I'm talking at most we've used about 6 litres of water for all of it and then chiselling it out. The plan for the floor is 3mm foam underlay and then 12mm laminate on top. I can't afford a pro unfortunately! Nor can I afford to rip up the whole slab and relay (not really got the time to account for that). Thanks for any advice, its greatly appreciated.
Ardex NA levelling compound. You may need to add aggregate to the mix for the deep areas if its over 12mm. That will be fine over ceramic and damp floors
Also, is there a cheaper alternative? Wary its double the cost versus standard 0-10mm levelling compound. Got a fair bit to put down.
Was going to use CDT. So its looking at £32.60, though I guess they may do it cheaper if I ask for trade price. My friend has an account there. I'm thinking i'll probably need about 10 bags so going from the £15 a bag and not needing the latex to £32 is a big jump. Its quite hard to calculate as its up and down a fair bit. So some it'll be 3mm some will be 10-12mm.
A cheap moisture tolerant compound is Tremco sx302 , Bostik screedmaster ultimate, Ultrafloor level it 2
Thank you. Where would you usually buy them? Seeing a lot of places I don't recognise on google. Wondering if i'd have somewhere local that stocks it (Warwickshire) as delivery will add to the cost a fair bit. Out of interest, why does it need to be moisture tolerant? Is that because I've used water to stop the dust? Assume that gets absorbed by the slab and takes a while to come back out?
oh and would just putting a thin screed down be an option. I could do minimum of 10mm across everything but i'm wary of doing that over tiles. I guess I could take them all up with the sds hammer drill...
If its not moisture tolerant and you ever get water or moisture in there it will blow off the floor. And its already damp yes. Ardex Na will work over wet screed. Some of the cheaper ones wont.
How long would it take to dry out? The slab is 20 years old so the only wet bit is from when we've been knocking it back and thats only in one corner of the room, its also the bit that needs the least compound as its already at the height we need it so just needs a smoothing layer over the top.
True. Would one of those cheap pin testers work or alternatively, could I stick a square of plastic down and see how it goes overnight and if there is any condensation on the underside in the morning.
You need a hygrometer or tramex to give you a accurate reading really. Or just use a moisture tolerant levelling compound. All of the above should work. The floor needs to look dry at least for most of them. I would take all the tiles up too as they can lift with damp/trapped moisture
Yeah it’s definitely looking dry. We only used a bit of water for it to stop the dust. Given the amount it kicked out it probably didn’t get a chance to go that deep as the settling dust would have absorbed it I think. I get where you’re coming from with the tiles but these ones have been down 20 years and despite the slab dropping they’re still absolutely rock solid. Despite being covered (badly) with foam underlay and laminate before. if I take the tiles up the amount of compound I’d need to level would be huge. To the point where it’d probably just be better to put a screed over the top. At its largest it’d be about 50mm for about 1m2 and then another 3m2 at about 30mm. Then the other 8m2 would vary between 5mm and 20mm. The worry with the screed is it’ll be really thin at one end as I can’t go too high or the patio door will sit underneath it.
