How to level slightly uneven concrete floor

[Todd Brewer]

The concrete floor in my shop is in good condition but is is uneven. Any four legged tool (aren't they all?) wobbles. Is there a product that can be put down to level the floor? I am aware of self leveling concrete. My concern is where the leveling compound gets very thin (at the high points). I'm convinced concrete levelers will fail at these thin points, but maybe I'm wrong. I'm thinking some sort of epoxy or ??? would be better. I'd estimate the height difference is less than 1/4" but it varies enough over short spans to cause tools to rock.

Shimming tools that move around is a pain. I would hate to have to hire a contractor to cut out the slab and pour a new one. $$$!

Let's just say the original contractor is not welcome or recommended.

An epoxy that can tolerate thin and thick areas would be ideal. But some other product that could later be epoxy coated would also be acceptable.

Any product recommendations?

[Bob Lloyd]

There are a number of cement based and expoxy based products available which would work in your situation. I cannot recommend any specific one but generally they are applied in a minimum thickness of 1/4" and up to 1"-1.5" thick depending on the product.

[Todd Brewer]

Bob, Thanks for the reply.

The problem is I only need to fill the low areas, so the product would have to feather out to nothing or very very thin. My 1/4" estimate is a guestimate over a 4 or 5' span. But even the area under a router table stand will wobble. I'm thinking an epoxy or other coating that would tolerate some thicker and thinner (very thin) regions.

[Michael N Taylor]

Find a commercial supply company that specializes in rebar, forms and all concrete related products. They can advise you with the best solution for your problem. We use Weld Crete for years as a bonding agent and it really makes the patch adhere to the old concrete but is fairly expensive unless you have a lot to do.

[Kyle Kaldor]

Todd, I had the same problem in my garage with a little different scenario. I had spalling in my floor that was patched by the previous owner with some junky concrete patch kit that was chipping. I ended up breaking up all of the patches and putting in an epoxy filler by EpoxyMaster https://www.epoxymaster.com/product_info.php/cPath/13/products_id/109

This stuff is not cheap, but I felt it was the only way to properly patch and feather out to basically zero thickness without getting the same result as I had before. I ended up adding sand to the epoxy to add volume. This made it very thick and paste like, but I feel very durable. It wasn't the easiest product to apply as it wanted to stick to my trowel more than the floor. After patching I used their epoxy floor kit to seal it all in and make it look nice ;) Good luck with your floor!

[Fred Belknap]

I have worked with concrete a lot and like you I'm not convinced that the levelers will last where it is thin. Concrete can be ground down which is a mess but it will work, I don't like how it looks. Have you considered putting down sleepers and plywood over the concrete. I wouldn't put to much blame on the party that poured the concrete, there are a lot of thing that can go wrong on a concrete pour. Temperature, humidity, supplier and how he stores his sand and gravel, how long the cement in the concrete has been in the silos. It all has to work together to get a good pour and sometimes it just doesn't happen.

[Carl Beckett]

I have worked a fair bit of concrete (my summer jobs in HS), and echo your concerns on thin leveling materials (they just dont hold up, unless used under ceramic tile but then they are more of a spacer)

So I would suggest: use the leveler. But then put down tile. Or composite hardwood flooring. (I know - you are going to have to convince your wife why you 'need' a floor in the shop that is nicer than the house!). (or maybe you could find those commercial vinyl tiles? - but the pressure point of machinery legs may transfer right through these as well)

If you want a softer surface, sleepers and plywood are a great solution, and many people here do it intentionally to reduce fatigue/back pain, and also protect the sharp edges of tools when we drop them.

[Jim Andrew]

Concrete suppliers usually have about any product available that you need. Why not just put a spot of filler under the tools where you need it? Probably the floor is ok to walk on. The patch products that contain latex usually work in thin layers. You can also coat the surface first with a product that makes the patch stick. Or, you could put a layer of about 1 1/2" thick over the floor after coating the floor first with a bonding agent. Some concrete finishers use a power trowel with attachments to the blades that make them cut in slightly, so that they level the floor when the concrete is the right consistancy. They then take them off and go with the smooth blades to make the finish.

[Todd Brewer]

Thanks for all the suggestions.

The floor is in good shape, it's just when I move mobile tools, the tools will wobble unless I shim them. They don't wobble a lot, but none-the-less they do wobble. I have no problem shimming stationary tools if they wobble, but having to deal with the mobile tools is kind of annoying. I was hoping the epoxy floor coatings or something similar might work. Maybe this is normal? Maybe I expect too much?

Perhaps some grinding followed by an epoxy coating will work.

Kyle, the Epoxymaster product is very much the type of product I had in mind. Up to 1/4" thick which should be enough. I'll check that out. Thanks!

[Phil Thien]

...it's just when I move mobile tools, the tools will wobble unless I shim them...

Are you certain that the stands themselves don't deserve some of the blame?

It would such to go through a ton of work only to find out your tool's stands are a bit wonky and still require shimming.

[Todd Brewer]

Good point. I'll check. I'm not really too excited about the work to coat the floor. I may just deal with shims when tools move, which shouldn't be very often.

[Steve Meliza]

I have a similar problem in my garage, I usually just move around a little till I find a flat spot. What gets really annoying is when I'm building something big on the floor and can't use measurements referenced from the floor and it can mess with my ability to build straight and square.

[ian maybury]

There's big differences in cost and quality between different floor leveling compounds. BASF/PCI do some very good (if pricey) polymer containing ones out of Germany: http://www.pci.basf.co.uk/en/Products/preparationproducts/LevellingSmoothingCompounds/Pages/default.aspx Chances are they are available in the US too.

I've used these products many times, and more to the point have tried to strip one after a few years - next to impossible. They are extremely tough, bond like sh1t to a blanket if you use the right primer (very important), and the right one (there are grades for different thicknesses) is easily feathered out to 1mm or so. I've used other 'latex' based levelling compounds that didn't even come close in terms of working properties, bond and/or strength.

They self level down to 2mm or so, and are low viscosity and get most of the way to level on their own - but in practice a little help from a straight edge is a good idea. I usually set the levels in advance using masonry nails driven to the required depth as guides - leveled using a long and accurate level.

Proper preparation (wire brushing or better still cutting back to clean concrete with a concrete sander and vacuuming off of the dust) and use of the right primer (usually primer G - maybe two coats on an absorbent surface) is the key, as any shortfall in bond is likely to be more to do with the nature and/or condition of the surface underneath than the ability of the stuff to bond. Dust is deadly, and concrete that's not been sealed by a primer pulls the water out of a thin layer before it gets a chance to cure properly.

They are not recommended for use without some sort of covering layer, but it doesn't take very much - they say vinyl for example is OK on top. Or any sort of laminate or wood floor.

The issue is probably wear and dust production more than weakness, as the stuff is very strong - 30N/mm2 in compression which is similar to the strength of the concrete mixes used in heavily loaded/high wear floors and roads.

It would for example probably be well worth a try with just a good epoxy or similar floor paint on top for sealing......

ian

[Jim Finn]

I had a similar problem so I installed a wooden plywood floor for about $200. (I have a small shop) Love it.

[Don Jarvie]

Put me down in the wood floor camp.

[Todd Brewer]

Too many tools wobble so it has to be the floor. I do not look forward to putting down a coating.

[phil harold]

convert your mobile tools to three point contact
problem solved

[Lee Schierer]

Instead of feathering, why not add 1/4" or so more tot he leveling material and not have to worry about feather thin spots spalling off.

My understanding is that if you use the correct clean up and bonding agent that the leveling compounds with work very well.

[Todd Brewer]

Three point tools occured to me but not always a good solution. I don;t want to add too much overall thickness if I can help it.

I need to find a local supplier of coatings. Not a Home Depot or Lowes. Otherwise I will live with what I have. It's not that bad, but if I could improve it without too much hassle I would.

[Don Jarvie]

How out is out? You haven't stated how unlevel it is, 1/8", 1/4" or larger. Is it high in the middle and lower to the sides, wavy, etc.

If its only off by 1/8" or so try some floor leveler and see what happens. If it cracks then you need to consider a wood floor. The wood floor will work fine with the floor leveler since it will spread the force across the floor and not just on 1 area where the machine is.

I have a 20x20 shop and my wood floor cost 700.00 or so and that was 3/4 OSB, pressure treated sleepers, insultation, plastic, screws and paint. I mainly did it for insulation but my back has felt better also.

[Todd Brewer]

How out is out? You haven't stated how unlevel it is, 1/8", 1/4" or larger. Is it high in the middle and lower to the sides, wavy, etc.

If its only off by 1/8" or so try some floor leveler and see what happens. If it cracks then you need to consider a wood floor. The wood floor will work fine with the floor leveler since it will spread the force across the floor and not just on 1 area where the machine is.

I have a 20x20 shop and my wood floor cost 700.00 or so and that was 3/4 OSB, pressure treated sleepers, insultation, plastic, screws and paint. I mainly did it for insulation but my back has felt better also.

It's not that bad, just enough that four legged stands/tables wobble. Not sure I want to put down a wood floor. However, I should give it some thought. I haven't built any cabinets yet so now is the time to do it. I'd have to have a slope or slight step down at doorways though. :(

I need an auto-leveling product that can tolerate 1/8" thickness or so. I would think epoxy based would hold up the best if it can tolerate the variation in thickness (paint-thin to 1/8" or so, maybe a hair thicker).

[Todd Brewer]

Instead of feathering, why not add 1/4" or so more tot he leveling material and not have to worry about feather thin spots spalling off.

My understanding is that if you use the correct clean up and bonding agent that the leveling compounds with work very well.

Lee, good point. I can tolerate 1/4" or so. I just need to find the time to find the correct product. :)

[ian maybury]

One reason not to go extra depth is that the stuff costs a fortune. That said it is the best way to get a nice flat and seamless looking floor. Don't forget as I said before though that while it'd be hidden in this case it's very improtant to do the work needed to get a good bond. i.e. proper cleaning, dust removal and priming.

[Todd Burch]

So, this thread begs the question... how do you contract for a "flat, level" concrete floor in the first place? Can this be written into a contract? Should a commercial contractor be used instead? What's reasonable for non-flat or wavy? My dad's house is terrible - he used a budget crew. Had to buy a demolition hammer to knock off high spots before we laid tile.

[Jamie Buxton]

So, this thread begs the question... how do you contract for a "flat, level" concrete floor in the first place? Can this be written into a contract? Should a commercial contractor be used instead? What's reasonable for non-flat or wavy? My dad's house is terrible - he used a budget crew. Had to buy a demolition hammer to knock off high spots before we laid tile.

I've wondered about that too. Clearly it is possible to lay a flat concrete floor. Nearly every commercial or industrial building built in this area in the last forty years has a concrete floor. They're flat. Some of them have multiple stories, all with flat concrete floors. Not only are the floors flat, but they generally have no expansion joints and no cracks, yet can be hundreds of feet in extent. I don't know how they do that either.

[Don Jarvie]

So, this thread begs the question... how do you contract for a "flat, level" concrete floor in the first place? Can this be written into a contract? Should a commercial contractor be used instead? What's reasonable for non-flat or wavy? My dad's house is terrible - he used a budget crew. Had to buy a demolition hammer to knock off high spots before we laid tile.

You hire real cement guys who do this all day.

If you are looking for a leveler to basically cover the whole floor and make it level then you have to buy a good brand that won't crack at the paper thin areas.

[phil harold]

So, this thread begs the question... how do you contract for a "flat, level" concrete floor in the first place? Can this be written into a contract? Should a commercial contractor be used instead? What's reasonable for non-flat or wavy? My dad's house is terrible - he used a budget crew. Had to buy a demolition hammer to knock off high spots before we laid tile.

Flatness and levelness can be specified in the contract
an example would be 1/8" in 10'

many contracts for flatwork in residential are not specific on flatness as where commercial jobs get very specific, and measurements are made withing 48 hours of placement

[Todd Brewer]

So, this thread begs the question... how do you contract for a "flat, level" concrete floor in the first place? Can this be written into a contract? Should a commercial contractor be used instead? What's reasonable for non-flat or wavy? My dad's house is terrible - he used a budget crew. Had to buy a demolition hammer to knock off high spots before we laid tile.


I've wondered about that too. Clearly it is possible to lay a flat concrete floor. Nearly every commercial or industrial building built in this area in the last forty years has a concrete floor. They're flat. Some of them have multiple stories, all with flat concrete floors. Not only are the floors flat, but they generally have no expansion joints and no cracks, yet can be hundreds of feet in extent. I don't know how they do that either.

In hind sight, I wish I had know to insist top quality concrete installers. I had no idea I would get "average" results. I say average because it isn't horrible, but I wish it were better. Every time I go into Home Depot or Lowe's I wonder why their floors don't crack, and I admire how flat they are, or at least how flat they appear to be (I haven't moved any four legged equipment around at either store, LOL).

[Tim Howell]

I have the same problem. So I used 1/2' threaded rod, put a foot on one end and 2 nuts on the other locked together. I use my drill set on low clutch to set them and it all hold fine. I ran the threaded rod through long threaded couplings or unuon what the correct name is and mount them to the frame. Keep them as close to the floor as you can and still get moving clearance. They are simuliar to these. pic- You could try floor locks too. I have one on my rollaway from the old aircraft mechanic days. photos from here - http://cplauman.thomasnet.com/category/caster-accessories (http://cplauman.thomasnet.com/category/caster-accessories)

[Fred Belknap]

I admire how flat they are, or at least how flat they appear to be (I haven't moved any four legged equipment around at either store, LOL).

You might be surprised how out of level they are. When the finishers use the motor driven trowel machines the floor usually end up much leveler and smoother but they don't work miracles.

[Jim Andrew]

It's amazing when they use the power trowel with the "teeth" on the blades. Don't know the proper name, but have seen these teeth type attachments they put on the power trowel, run over the slab at the proper stage of the concrete, then take them off and go over with the smooth blades. They teeth type level the slab, or at least cut the high places off, so they get a fantastic flat slab.

[Ole Anderson]

Anyone have experience with having a contractor come in and grind your floor flat? Instead of filling the low places, lower the high places. A fully ground concrete floor with a sealer looks pretty sharp. Kind of like refinishing a beat up oak floor. I have no idea on the cost vs an epoxy self levelling material.

[Todd Brewer]

I have the same problem. So I used 1/2' threaded rod, put a foot on one end and 2 nuts on the other locked together. I use my drill set on low clutch to set them and it all hold fine. I ran the threaded rod through long threaded couplings or unuon what the correct name is and mount them to the frame. Keep them as close to the floor as you can and still get moving clearance. They are simuliar to these. pic- You could try floor locks too. I have one on my rollaway from the old aircraft mechanic days. photos from here - http://cplauman.thomasnet.com/category/caster-accessories (http://cplauman.thomasnet.com/category/caster-accessories)


I've been thinking about how to easily level a machine or table when moved. Not a bad idea. I have my drill press on a shop fox base. It has adjustments that force a rod down to take the load off the wheels and theoretically hold the tool in place. However the rods are held in place by magnets and the sleeve for the rod is a bit too sloppy, so the tool can rock back and forth. Not really an issue for a drill press as most activity is vertical, but I would be very disappointed with that base on a table saw, too much rocking.

[John Lifer]

Anyone have experience with having a contractor come in and grind your floor flat? Instead of filling the low places, lower the high places. A fully ground concrete floor with a sealer looks pretty sharp. Kind of like refinishing a beat up oak floor. I have no idea on the cost vs an epoxy self levelling material.
If you can empty the shop, this is a good alternative. Get a quote on polishing the floor. Not really cheap, but a very good alternative to trying to fill or level by adding materials. Had a company come in and do a 30x40 for about $3 a sf. I'd do this rather than fill. Won't pop loose in 3 yrs.

[tony maida]

I have worked in the commercial institutional bldg field for over 25 years . Fixed a lot of concrete floors . It all comes down to how much you want to spend. There are several high performance concrete topping suppliers out there ( mapei and ardex to name a few ) where you can go from 1/2" thickness feathered to nothing .
It all depends on your surface prep. You may not like the cost.

I would suggest you seek out and rent a concrete surface grinder ( a real one ) and grind down your slab , acid etch or shot blast the surface and epoxy paint it . Cheapest way to go for a good repair.

my 2 cents

[Todd Brewer]

If you can empty the shop, this is a good alternative. Get a quote on polishing the floor. Not really cheap, but a very good alternative to trying to fill or level by adding materials. Had a company come in and do a 30x40 for about $3 a sf. I'd do this rather than fill. Won't pop loose in 3 yrs.

I think this is the best solution. Something that may sting now, but will not come back to haunt down the road.

[Phil Thien]

If you can empty the shop, this is a good alternative. Get a quote on polishing the floor. Not really cheap, but a very good alternative to trying to fill or level by adding materials. Had a company come in and do a 30x40 for about $3 a sf. I'd do this rather than fill. Won't pop loose in 3 yrs.

Yeah, but how flat can they get it? It would seem to me that grinding a floor flat may be about as easy as using a rotary sander to flatten a rough-sawn board.

[Curtis Myers]

Have you considered making three legged stands/carts. Four legged stands/bases can wobble but three legged ones will not.
My 14 Powermatic mobile base from Powermatic is a three wheeler with no wobbling issues.
Any tool which has inherent vibration (scroll saw, lathe etc...) can be magnified on a wobbling four legged stand.
I built a heavy wooden three legged stand for my scroll saw specifically for this reason.