Old chestnut - Self levelling compound

[GMM]

Laid a bag of SLC (Wickes latex) yesterday. Having read the feedback on their site, I followed the recommendation to add an extra litre of water to help it flow better. Not a bad outcome but could be a lot better. In particular, it still has some grooves in it from the rake I used to move it around, so it must have set faster than it flowed. Certainly not as good an outcome as the last time I did it. Anyway, I have to put a second bag down (it never seems to bring the level up as far as the blurb claims does it?) so I want to get a decent final result.

So, in the opinion of me learned friends here: a) Is putting more water into the mix a good or bad idea? b) Is there a better way to move it around? I have been considering a board with a few screws driven through to space it from the floor by a few mm but that might simply make it follow the contours of the first coat. c) Is it a good idea to use more primer between two coats or will a spray of water be sufficient? I have plenty of primer but you never know...

The floor is only about 2sqm but I would like to get a nice flat surface to make doing a decent job of tiling easier.

[Tim Watts]

On Monday 18 March 2013 20:07 wrote in uk.d-i-y:

That (t-bar with screws) is what I did. However, I was using F Ball Stopgap

300 which flows *very well* and requires a neoprene primer to go down first that makes the substrate waterproof, so it does not suck water out of the compound.

Even then, it flattens a lot better if applies at > 4-5mm compared to trying to get 2-3mm.

The other trick it after the initial spread, is to agitate it with a spiked roller. Stopgap 300 has a working time on a warm day of about 20 mins - thereafter it sets very rapidly.

Persoanlly I'd advise the Stopgap and primer if you need to put another bag's worth down. If ordering it is too much trouble, then perhaps priming the existing substrate with dilute SBR, which *should* be compatable with latex screed, would help to reduce suction and probably give you more fluidity and better working time.

I would not overdo the water - do that may lead to a weak set product.

What primer do you have?

1 bag of Stopgap would pour straight onto that and give you about 6mm of covering - more than enough to self level once it's wetted everything - it's so runny that you would need to dam the doorway(s) - I stuck some wooden batten down with expanding foam - you could use blutack and/or plastercine, but seal every last hole. Made that mistake...

the only fly, is you need to buy a lot more of this

than you will actually need (that's the primer).

[John Rumm]

I have not usually bothered...

I normally just use a 2x1 or similar to wire it around and trammel it off roughly level.

Not tried -normally I try to do it in one pour to the full depth (even f that means sectioning bits of floor off.

[GMM]

Ahh...I must admit I had completely forgotten that the F Ball stuff is recognised as the dog's danglies! Sod's law always dictates that you can't just scoot round the corner and pick up the good stuff, which is why I just picked up the Wickes stuff (which had worked fine for me before). Now the challenge is to find a way of getting hold of some during a week when I'm not going to be home for any deliveries etc.

The primer I used was the Wickes acrylic stuff which, having bought it at great expense (like the F Ball primer, you have to buy more than you need), I must think of an alternative use for. Although (interestingly) the same colour as the Ball primer, I suspect it's a completely different thing.

Good advice on damming the doorway: I still have the dam in place from yesterday when, disappointingly, the level didn't come high enough for it to be necessary.

[GMM]

When I've done this before, I pushed it around with a float to make sure everything was covered and it then flowed to a smooth finish. This time I invested in a new rake (for reach as much as anything) and used that to push it around, spreading it with the flat back, then running the teeth through it. I was a bit surprised that some of the grooves from the teeth of the rake didn't flow out as they were quite narrow.

The last time I did this, on a very off-level floor, I built it up with

3 applications. Not on purpose, but because I completely udnerestimated what it would take. That time, I didn't think of anything as fancy as priming but just threw it down. It seemed fine for the rest of the time in the house, having tiled over. Perhaps I'm over-thinking that one (!)

[harry]

I have always just spread it with a float. I think you get marks left if you mess with it after it's started to go off. You need to put it down straight away after mixing. Goes off quicker if it's warm too. Goes off quicker if the substrate's very dry. Needs to be thoroughly mixed.

[harry]

Oh! Goes off quicker if it's a very thin layer too.