Grinding before self-leveling

[Timo]

Hi,

I am new to floor work. I am going to self-level my basement concrete floor before putting Barricade subfloor tongue and groove panels and luxury vinyl on top of that. I looked at Mapei or Sika self leveler compounds and both manufacturers say to grind the floor to CSP #3 profile.

I renter Husqvara PG280 single head grinder to do the job. As I can't really tell what's CSP #3 vs #4 etc I can't definitely say whether the floor has been ground to the appropriate level of "roughness".

My question to the knowledgeable folks here is this - how crucial is it to have cement ground exactly to the level that the manufacturer of the self leveler recommends? What can potentially happen if the floor is not sufficiently ground or not ground? I am applying self-leveler across the entire surface.

THank you much in advance.

 

[Ernesto]

A diamond head is sufficient. http://www.tccmaterials.com/userfiles/file/ConcreteSurfaceProfiles.pdf

 

[Timo]

Thanks, Ernesto. But what can possible happen if the underlying slab is not sufficiently ground? Will self leveling underlay crack under foot traffic?

A diamond head is sufficient. http://www.tccmaterials.com/userfiles/file/ConcreteSurfaceProfiles.pdf

 

[Ernesto]

Just about any diamond head grinder will get ya to a csp-2 -3. The reasoning is they don't want you going over a really smooth surface or a surface with bond breakers on it like paint and old glue or it won't grab and could come loose . Make certain you use any primer they may recommend. All SLC's need a primer as it helps the stuff flow and won't curl at the perimeter.

 

[Timo]

Thanks, Ernesto. I included a picture of what it looks like now. Not perfect grinding but it was a pain to get it even to this point. Do you see any concerns with how it is now?

Thanks
Michael

Just about any diamond head grinder will get ya to a csp-2 -3. The reasoning is they don't want you going over a really smooth surface or a surface with bond breakers on it like paint and old glue or it won't grab and could come loose . Make certain you use any primer they may recommend. All SLC's need a primer as it helps the stuff flow and won't curl at the perimeter.

 

[Ernesto]

Looks great Timo. Why self leveler, not flat enough?

 

[Timo]

Thanks.

Well... there aren't really any huge peaks and valleys but all over the floor I have a number of minor imperfections. I already started laying barricade subfloor boards to just discover that I need to practically put shims under almost every single one of them. And in some spots no matter what I tried I still got a bit of give when I stand on the board. I believe there isn't anything larger than 1/4" but it would just drive me nuts if I stepped on a floor and it had give.

Thanks,
Michael

Looks great Timo. Why self leveler, not flat enough?

 

[Ernesto]

Well SLC can really help but if your not experienced at it you can have the same issues. I only use it for small areas. In larger areas you really need a crew with a pumper and guys with golf shoes on pushing and raking it flat. Typically we go for flat not level. Big difference.

 

[Nick]

They made us use Football shoes at the Ardex training center .. You do need the guys and the pumper ..

 

[Timo]

My largest space in the basement is about 400 sq ft. What if I sectioned it off in areas of say 100 sq ft? Was planning to have someone assist wth mixing while I was poring and smoothing the cement.

 

[Ernesto]

400 sf is doable with two people. Just have plenty of buckets ready to go. Make sure you use the required primer.

 

[highup]

400 sf is doable with two people. Just have plenty of buckets ready to go. Make sure you use the required primer.

Two people who have done this before.

 

[highup]

My sarcasm in the prior post was serious. I'd recommend 4 people who are somewhat good with mechanical thinking. Be sure everyone is all aboard from the beginning so that the process 'pours' fast and steady. A mini marathon of sorts.
If you have one too many people, that's OK. One person not enough is a bad day.

 

[Timo]

Thanks, Gents. So is it a bad idea to try and separate the larger room into smaller sections with something like weather strips or something of sorts?

 

[Jon]

My sarcasm in the prior post was serious. I'd recommend 4 people who are somewhat good with mechanical thinking. Be sure everyone is all aboard from the beginning so that the process 'pours' fast and steady. A mini marathon of sorts.
If you have one too many people, that's OK. One person not enough is a bad day.

What some of the guys here do is have big plastic rubbish bins full of water handy so that they can just scope the water out without having to fill the bucket of water each time

 

[Ernesto]

Thanks, Gents. So is it a bad idea to try and separate the larger room into smaller sections with something like weather strips or something of sorts?

Sure, you can nail down some wood to separate the pours but remember you need those edges to match up. Which it is why its kinda easier to just pour an entire room. However you could come in and grind down the height difference.
There are methods like drilling in the concrete and molling screws set to the level your trying to achieve, and or then leveling to the tops of the screws or string set to the screws run across the room. It's kinda technical.

 

[Timo]

Well, well... so I did a small room and a hallway in my basement. The job itself went not bad but I noticed when I was mixing the SLC it had kinda black oily spots in it... I mixed for a bit more than the 3 minutes indicated in the manufacturer instructions but also didn't find it as liquidy as I saw from the vendor's videos (which is fine).

Anyway... I started reading about some sites and found that both it is not recommended to use it past it's expiration date (had no idea cement had an expiration date). Of course, nobody say why exactly. So went to see my bags and sure enough the expiration date listed is Oct 2016.

My question to your knowledgeable folks is this - is there really a harm in having "expired" SLC underneath your subfloor? Will it crack with time? Will it sink? Will it be less durable?

I will replace the remaining bags to complete the jobs with stuff that is less than 1 year old, but should I remove already applied cement and re-apply?

Thank you much

 

[Nick]

Bagged cement is not airtight and even if unopened should be used within a few months. Although again, the shelf life of individual bags depends on the conditions under which they have been stored. At best, correctly-stored, unopened bags might have a shelf life of up to six months.
As long as the cement is less than six months old, has no lumps and is a completely free-flowing powder, it should be okay to use for non-structural purposes. All structural jobs (ie. jobs that require maximum strength) should always use fresh cement.

 

[Ernesto]

Who sold you out dated SLC? Thats way way to old. I'd ask for my money back plus damages to remove it. Hope u have a receipt.

 

[Jeremy Shoning]

Just about any diamond head grinder will get ya to a csp-2 -3. The reasoning is they don't want you going over a really smooth surface or a surface with bond breakers on it like paint and old glue or it won't grab and could come loose . Make certain you use any primer they may recommend. All SLC's need a primer as it helps the stuff flow and won't curl at the perimeter.

I know I am really late to the game here, but.... An ICRI( International Concrete Repair Institute) Concrete Surface Profile(CSP) of 3 can only be achieved by shot blasting. It is considered a light shotblast. The texture of the profile has depth and cannot be created by grinding.
Take a look at this article. http://www.tccmaterials.com/userfiles/file/ConcreteSurfaceProfiles.pdf