Repairing & Levelling Concrete Floor In New Workshop

[Delaney]

Hi all.

I have moved into a new workshop and the concrete floor is all over the place. I would like to take out the slope and make it flat.

I've spoken to several screed contractors and several concrete contractors, not to mention suppliers of both materials and the variation in opinion is large.
I have several machines that are 600-700 kilos in weight so the surface needs to be strong.

I have been told by concrete layers and suppliers to stay away from screeds like sand and cement as they will not be strong enough.
I have been told if I lay cement, C30, the minium thickness needs to be anywhere from 150mm to 75mm. That I would need to include mesh to stop cracking and
will take a week plus to dry. This seems unpractical.

Liquid Screed types tell me that I can lay a liquid cement that can be put down to bonded cement as thin as 30mm and go up to a thickness of 300mm (on some products ‘silka’). This is more suitable due to there being a slope of roughly 150mm across the floor from one side to the other.

My concern is that if I lay a liquid concrete, it won't be strong enough, although 'FlowCon’ is rated at 55 newtons, is C40, min depth 30mm and for 7 m3 would cost £2000+ VAT.

Looking for advice and or experience with this type of work. Just don't want to lay something that won’t work.
The existing concrete it stable, its just a farm so the unit was a chicken shed and the concrete not poured for flatness.
Someone has already tried to lay some self levelling, which is cracking and not level at all.

Here is the existing floor.

 

[ChaiLatte]

Much of the success from whatever you choose will depend on its interaction with what is there already.

That means the sounder the existing, the cleaner the existing, the more dust-free the existing, the more keyed the existing is, the better the new will bond to it.

The contractor laying it will not care - they will pour onto whatever is there the day they arrive. Hence, you have to assume responsibility for the preparation work. That could be as minimal as a good jetwash but could extend to repairing any dodgy parts and keying the surface with one of these:

https://www.wh-surfacepreparation.co.uk/f20-hire-200mm-floor-scabbler-spe-bef200-electric/6

Another great influence on the success is how the material is cured after laying. The contractor will do nothing at all on that front. Again, you can take responsibility for that. Sodium silicate solution is a great curing and dustproofing chemical and is cheap. The challenge with spraying it is how you reach the entire area of the floor. The first spray needs doing on the day the material is laid, after it has gelled over. That might mean overtime for you if the laying does not finish until 1600h.

You should not expect to use the floor the day after it is laid. Spray again as early as possible the next morning and cover with plastic sheet to keep it moist. On the second day after pouring, it would probably be OK for light use.

 

[Sachakins]

If that was just a chicken she'd, there's no telling what sort and quality of base it's both on and made of.
It may benefit you to dig a few test holes spread out about the floor, to a depth of about 300mm. Just to check you are working from a good start point.
It would be a disaster to spend a few grand, only for it to fail quickly, because the sub base collapses on you.

 

[niall Y]

Would an epoxy screed not be suitable? The maintenance crew in a factory I once worked at , used it under all the heavy duty machines that they installed.

 

[dizjasta]

If you have any doubts concerning the strength of floor slab try contacting someone local that can provide results from a Schmidt Hammer test.

 

[Delaney]

If that was just a chicken she'd, there's no telling what sort and quality of base it's both on and made of.
It may benefit you to dig a few test holes spread out about the floor, to a depth of about 300mm. Just to check you are working from a good start point.
It would be a disaster to spend a few grand, only for it to fail quickly, because the sub base collapses on you.

I can only say that the concrete floor that is there, is part of a huge concrete slab, that contains at least 300 m2 + of units.
Mine is in the corner and so the concrete slopes off.
I have to bare in mind that it’s not my workshop and it is cheap but the floor as it is, is very uncomfortable to stand on for any amount of time.

I had thought about hiring a concrete grinder to at least try to remove the smoothing compound laid incorrectly by the previous tenant and take out some undulation in the concrete base.

The concrete base that is there is not new and if a new surface is applied and cracks, that would likely still be far better than what is there, unless we’re talking about complete failure, which surely would mean the concrete sub floor is on the move, which I doubt it is, after all this time.
Or are you implying that the weight of the screed, could cause issues with the ckncrete?

 

[Ollie78]

My workshop is inside an old barn with a deliberately sloping floor.
The previous guy who had it basically just built a complete insulated building inside the barn starting with levelling the floor, there is about a 400mm step at the front. Just joists and chipboard t and g, I have some heavy stuff in there and it is fine ( getting it in and out not so much ).
You could do similar, just ingnore the concrete and its lack of level by building a nice new level floor on top handily skipping over all the lumps and bumps.
Might be cheaper than concrete and you can insulate under it.