Screeding Disaster

[John Smith Esq.]

Used Benfer 2-50fl on a new concrete floor primed with SBR. Greatest depth around 15mm. Builder who has used it is experienced and used the product before, albeit less depth. He measured out correct amount of water. Doors closed. Not particularly warm in the room. Anyway, he has run his spiked roller over it and it's made a right mess. It is as though it has gone off too quickly and not been wet enough when spikes went over. He says it was hard to work with. In thicker aras anyway.

It looks nothing like latex leveller I've seen and used before.

Thoughts?

Do we try to smooth out and then go over it again tomorrow or get the lot up and start again?

 

[dazlight]

Should have used primer.
Should have mixed it quickly. Someone mix and keep them coming and one putting it down.
Never heard of that compound so can’t comment if it’s any good.
The best wet edge compound is ardex k40 flow

 

[johnny2007]

In warm weather it needs mixing a bit more watery, it says in the instructions as well.
Experienced flooring tradesmen can go by eye and know how thick compound needs to be.
Once he realised it was too thick he should've shoveled it out and start again.

 

[John Smith Esq.]

So basically, after the photos above, he sprayed water on it and smoothed off to get rid of big holes and spiked surface. I don't know how effectively this will have removed holes below surface. He has then poured again over the top of it all about an hour later. Today it looks like the attached.

It is impossible to speak to Benfer without contacting Italy. I called Mapei who do a similar product and they said you shouldn't add layers to screed until the first layer has fully cured (like 24 hours or more) and should use primer again.

Builder hasn't done this. Put down the first layer and run spikes through it after it has started curing, basically shredding it up. Then dampened this to smooth off with his glide tool. Unclear how it now is within the layer below the surface - could be a load of holes hidden below. Then poured a new layer an hour later, before first layer has cured and with no primer. And it still doesn't look great.

If it is structurally sound I'd just sand off and leave it. But presumably might not find out if it is dodgy until possibly after floors, skirting boards, etc have all gone over the top? So do we bite the bullet, take the lot up, or see how it is? 200kg of screed now to get up.

 

[opps]

I doubt you will be able to sand it with regular sandpaper. A Carborundum Stone will work but it will be slow.

You can hire floor grinders/sanders. Never used one personally.

 

[dazlight]

In warm weather it needs mixing a bit more watery, it says in the instructions as well.
Experienced flooring tradesmen can go by eye and know how thick compound needs to be.
Once he realised it was too thick he should've shoveled it out and start again.

No it doesn’t as that weakens it and you get a soft finish.
Most bags will have a the max and min of water to go on. 4.5ltr - 4.75ltr. Never go above that.

 

[dazlight]

I’d be putting another coat over that floor. What you laying over it ?

 

[johnny2007]

No it doesn’t as that weakens it and you get a soft finish.
Most bags will have a the max and min of water to go on. 4.5ltr - 4.75ltr. Never go above that.

You go to the max when hot.
Adding 100ml extra doesn't make any difference in my experience when working in extreme heat.

 

[dazlight]

We keep it in the shade , black out the windows and never had a problem. Most of the time we fit LVT so can’t have direct sunlight on it while fitting it.

 

[John Smith Esq.]

I’d be putting another coat over that floor. What you laying over it ?

Underlay and laminate.

The surface right now is a bit of a mess. And has added unevenness in levels. Assuming it is structurally sound (I guess we could have a good stamp over it on Monday to see), I'm thinking we hire a floor grinder, even it all out, see how intact the surface is and then see where we are with levels. Possibly then go over it once more but do it properly this time...

I wonder if the screed surface remains bonded after being sanded or grinded? Like concrete. Or does it just become crumbly?

 

[dazlight]

Be fine grinding it or sanding it if the primer was done correct.

 

[John Smith Esq.]

Be fine grinding it or sanding it if the primer was done correct.

Yeah the primer was done correctly. On the first part anyway. But the first screed layer was covered with a new layer after an hour or two - so not cured - and wasn't primed. As far as I know, you're supposed to let a first layer fully cure, then prime it, then start a new layer on top.

If we decide to just take the lot up, all 200kg worth, is there a type of heavy duty planing tool we can hire, that would cut through it all quickly and suck up all the dust?