Got 8 bags of Cempolatex that's going down in a couple of weeks.
Will be using a series of guide rails to ensure correct levels and laying in
1-.5m wide stripes for practical reasons (large room).
One thing occurs to me: I have engineered a controlled slope in the centre section of the room (12mm in about 2m TBC)[1].
The compound will be going on between 1mm and 8mm thick typically in this region. Am I likely to have trouble keeping it on this slight slope - ie is it likely to try to slump towards the lower end? The top end is likely to only be 2-4mm thick.
[1] Levelling the whole floor is out of the question - I would need 10 bags just to sort out half the room, then probably another 6 to complete. And there would be level mismatches at the hall door of 8-10mm.
Shouldn't be a problem. It basically stays where you put it, and doesn't self level. Where I had trouble was joining the separate sections. It sets hard quite quickly and you may find it difficult to smooth the edges where the guides have been. I think I had to use a disc sander at one point, but I had mistakenly left it overnight. Using dabs of screed rather than "rails" might work better. If you lay a straightedge down and pack it out underneath, you should get an accurate height.
That depends rather on the compound. I used some F Ball Stopgap 300 last weekend which really is a self-leveller, rather than a self- smoother. Amazing stuff. Slight push with a trowel to spread it, spiked roller, and 5 mins later it is flat and level.
The others I've used (Sika, and BAL Multibase) behave more like your description.
Mapei Ecoplan Ultra is another one which is supposed to be a real self- leveller.
Yes, best to get at it while it is 'green' and can be scraped with a trowel.
My tip: in this weather, cover the windows to ensure shade - if the sun gets to it it will go off before you know it.
DAMKHIT, but it involved cursing, a shovel, something awaiting disposal on my patio which looks a bit like a grey elephant dung sculpture, and a few extra bags of SLC (at which point the Stopgap came into the equation, so it wasn't all bad)..
It helps to agitate it a bit, gently, after the spreading, which encourages levelling, and it releases any entrained air to stop bubbles on the surface. It's a trick of the trade, like pin levellers/ wiper blades etc, rather than a requirement which would be mentioned on the bag.
Interesting about the Wickes stuff, I wonder who makes it. What kind of area/depth did you do, and what kind of error against a level did it end up with?
There are so many of these things, and they seem to vary hugely - I've got limited first hand experience but it bears that out. Pro tilers and karndean-type (even fussier requirements) installers certainly think so as well (and know a lot more than I do about it). The latter can get away with very little in terms of flaws in the substrate, and is where I got the Stopgap 300 tip from.
Stuart Noble coughed up some electrons that declared:
Thanks Stuart. Sounds promising.
I'll watch out for the edges. The guides will be ali channel, set so that a scraper bar levels the screed to the *bottom* of the rail. Cling film will be used to ensure a release of the guide. Alternate strips will be done, the edges sanded or trimmed as necessary to remove any bits the crept up, then the remaining strips will be laid without rails (ie scraped level with neigbouring strips).
I'll report on the success of otherwise of this method. But it does have the advantage that all the pratting around is done "dry". Once the rails are set on their studs, it's *should* be pour n scrape. That's the idea anyway...
Yes, I used Cempolatex recently and was not impressed. As everyone says here, it does not really self-level. It's also very expensive for what it is. I hope to make up the dips by getting the levels right with adhesive before I lay the Marmox board! Maris
Ah. Good tip. There were a few surface bubbles, but the tile adhesive will cope with those easily.
It was a porch 6' x 3' approx. From the initial check with a level, one corner was down by about 10mm, rest of it was a roller coaster for a mouse. Hard to get a level when it keeps rocking, don't know where you are.
Ended up like a bloody billiard table, hence me being so impressed with the stuff.
The client had the porch built by a national DG company who initially quoted 'including base' but when it came to doing the job claimed it was 'base extra'. Harsh words were apparently exchanged & the client reckoned the base was put down in a rush.
I ended up with the Sika & BAL stuff basically trying to level it with a trowel, and then hoping the trowel marks would disappear- far too much skill required, so there were bits which were at least 2/3mm out. The F Ball stuff is consistently level to within a mm over the length of an 1800 level,and just so easy that I will never bother with anything else (assuming I need SLC again).
I rigged up a similar arrangement in wood for rendering a wall. I found it easier if the scraper bar was a couple of inches shorter than the width between the guides to allow some side to side movement. The angle of the scraper also needs to be constant as there is a temptation to rotate it to get a better edge. I still ended up with some shallow indents where the guides had been and these were more difficult to patch than deeper grooves. Your ali system might be more accurate Good luck with it. Won't half do your back in if you can't kneel between the channels :-)
The Marmox instruction leaflet says that a cement-based adhesive should be used so I bought some Screwfix 'No Nonsense' tile adhesive, which seems to meet the requirement. I'm using the Marmox to replace the 50mm screed that I have removed and which was in poor shape. I am installing a wetroom so I am having to incorporate a Marmox 20mm showerstone base, which means using combinations of Marmox under that to make up the level to 50mm. Marmox as a DPM? Hmm. I'm installing underfloor heating over the Marmox, by the way. Cheers, Maris
Interesting. The concrete under my screed is as rough as a camel's arse so I'm putting down 25mm SBR modified sand/cement screed to even that out, then marmox. UFH in the 2 areas where I'm back to the concrete as I have room for extra marmox. No UFH everywhere else as I decided I'll be bleeding heat away left right and centre.
It was Marmox technical who told me that marmox could be used as a DPM provided I sealed the joints (silicone or tape). I actually rang them to ask how to fix it to a damp subfloor. The said plug and screw, and if I prefered adhesive, I would need to speak to the adhesive manufacturer.
I did do that (Mapei) who recommended (but couldn't absolutely guarantee) Keraquick. So that's what I'm going with.
Are you sure they understood what a DPM is? Their instructions do say about sealing joints with silicone but I assumed that that was to stop water from the walk-in shower leaking into the subfloor i.e the other way round! Why is your subfloor damp? That's a bit suspect straight away. Strangely enough I'm finding strange things in my 20 year old extension (built by previous owner). I was drilling through the wall from inside at low level to take the waste and was getting damp sand coming back out. Has my cavity been bridged? Wondering whether to remove a brick/block at low level. The outside DPC is much higher than the inside DPC because the garden rises behind the extension. However not sure about the inside DPC at all - I thought it was the plastic membrane under the concrete slab turned up but it seems to be a DPC, in fact, not connected to the slab at all! Anyway, back to the subject in hand, I'm using electric UFH, which takes up very little thickness and will go in the tile adhesive. I'm using pebble tiles on top of the Marmox and am now getting worried about pressure on it impacting the Marmox because they recommend solid tiles! Cheers, Maris
Yes, they understood. They volunteered that it would act as a DPM as it was waterproof and vapour proof in either direction ;->
Not really. The house is nearly 60 years old and has variable dodgey floor construction.
In some parts there does appear to be a DPM of sorts under the screed over the concrete. In other parts there isn't. Under one bit of lino I lifted, it had been damp - black mould and dark patch on floor.
The same house has 12" foundations on clay - that's broken by modern standards, but the house has survived perfectly well.
It's just the old ways...
If the damp sand is lower than the DPC it's nothing to worry about - that's normal.
If it's above it may bridge, but the practical effects will vary - it might be no problem or it might be a serious problem. Depends how much bridging, how wet the outside wall gets etc.
The real test - do you actually have any damp problems inside in that area. If not, don't worry.
That sounds cool.
On the Marmox loading - it has a compressive strength of 30 tonnes/m2. I've got some - the foam is fairly soft but the glass mesh surface is rock hard.
Are you likely to get a seriously high point loading anywhere that could push your pebbles down?
Is this a bathroom? If so, perhaps you could mitigate it by putting the bath on bearer planks (I will) and perhaps using a normal tile under the loo base. Otherwise I can't see a bathroom area getting much other high loadings.
Kitchens would be different - table legs and worktop legs...
A 60 year old house should not have variable dodgy floor construction! cavity walls had long been invented by then (not that that has anything to do with floor construction but you get the drift).
The DPM should be under the concrete slab!
Erk!
Except that I'm not sure if the plastic is the DPC. By rights I should have been perforating the dpc/dpm with my drilling but I didn't come across anything.
I noticed that I made indentations when I knelt down on the Marmox to do something. Point loads definitely do have an effect.
Yes, it's a wetroom, with a shower but no bath. Maris
Generally et conct=rete slab is 'below damp' laid on hardciore and soil. If you dpm under that it waill rip and tear.
Normally 60 years old menas they painted the concrete with bitumen before screeding. Liable to fail in time. Also may be bridging if screed below DPC level on walls..
See above. It may be bitumen.
I laid slates and tiles straight on the screed here. Its fine. Just use waterproof grout. And tile up a fair way on the walls as well.
We have cavity walls. Just no consistent floor DPM. We do have consistent wall DPCs.
Look - don't mean to be rude, but can we drop it. My house is not upto modern standards - I don't care how it's supposed to be - it is as it is. Mostly it has no *serious* problems, just minor easily fixed ones (and the lack of DPM is minor and easily fixed - we are not swimming in a lake here, water ingress is mostly vapour)
On the whole, it's better built than most of the modern stuff: bricks through and through and decent timber and despite the lack of deep foundations and DPMs I would bet that it will outlive half the ticky tacky crap that passes for building technology these days.
Likewise - it is still standing. The only cracks are where some d*****ad removed most of the bricks under the fire opening lintel.
^^^^ !!!!
;->
Are your pebble tiles individual "pebbles" on a mesh that lay a bit like mosaic tiles, then you grout the tile as well as between all the tiles yourself?
If so, and if you are noticing point load indentations, then personally I would change the tile type. Same for mosaic. You have to lay them with a flexible adhesive and grout out of necessity with marmox.
With no particular assumptions on how much you weigh, 30t/m2 equates to a
100kg fat bloke standing on a 5cm x 5cm area, approx. It's easy to see how your knee made an indent as the area of contact is much smaller - 50kg would be a very thin bloke.
Therefore, I would reckon on 10cm tiles being the absolute limit on size - you need a margin for dynamic load vs static load (eg jumping).
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