leveling a VERY uneven basement concrete floor

[D K Woods]

We're purchasing a new home and looking into putting new flooring in. I plan to use a finished room in the basement as an office, and want to put in a 'hardwood' laminate floor. The problem is, the concrete in the basement in *extremely* uneven. I don't know a specific depth since I haven't pulled up the carpet that's current covering it, but I would guess some of the worst parts vary by maybe 1" over a 2' area. Positively wavy.

I've seen that Quikrete has a self-leveling floor resurfacer, but I don't know if it will work to that magnitude (possibly with several stages?). I also haven't found any indication as to how much might be needed for a given area -- or where to get it, or how costly it is. What kind of equipment is needed for this job? I've read that a power mixer, or a mixer tool on a power drill, is needed, as well as some tubs and cleaning agents. But I've also seen pictures of people using some kind of tubing/hose to pour the mixture. Is this necessary? Fortunately, the quikrete stuff allegedly does not need any trowling.

How difficult would a resurfacing project like this be? I'm new to flooring AND to concrete.

And finally, will the fact that this is an interior surface alter the estimated drying times? The room can be vented through a door into the garage. What about fumes?

Much appreciated!

-david

[Chris Lewis]

According to D K Woods :

I've fortunately not had to do anything like this, but I've heard some of the stories...

Perhaps the first thing you need to do is identify how much of a job this will be to do _right_, this is how you find out what magnitude of problem you're dealing with.

"Solutions" range all the way from just bridging an occasional dip with subflooring (ie: plywood sheet), all the way to laying and leveling a few inches of new concrete over the whole floor.

[Both my family and my inlaws have been thru the "pour a new floor" version. They needed it...]

Even _with_ seeing your floor, I'd probably not be a good source for recommending the right solution. How widespread is the problem? Is the floor generally flat with occasional dips/ripples, or, completely unflat (ie: different slopes thruout the floor)?

This is where I think it'd be a good idea to call in several professionals, each with different "solutions styles", get estimates, and find the best fit.

You're probably looking at several days for curing. Likely weeks (or even months) before covering with wood flooring over fresh concrete.

The fumes are unlikely to be a big deal (concrete "fumes" are just water evaporation...), as long as you have active ventilation.

[default]

It's going to be a pain in the ass, no matter what you do. How much headroom do you have to play with? The easiest/cheapest solutions (well, after just sucking it up and living with a bumpy floor, which wouldn't hurt you any) generally involve piling more stuff on until the floor is level, but if the ceiling is already at the 6'8" line, you'd be better off pounding the existing floor out, and pouring a new slab. What sort of dampness/water issues do you expect to have, how cold is the floor, and do any sections of the floor move with the seasons?

For concrete, it doesn't matter; it doesn't actually dry the way you normally think of drying, the water chemically combines, and it doesn't produce any fumes worth worrying about in this context.

-Goedjn

[MLD]

[raven]

Deeper is usually easier with topping mix. The self-leveling ought to work like that as well tho you're going to pay out big bucks.

You'll be working with an expensive product, doing a job you're unfamiliar with: Does this sound like a recipe for instant success?

You can continue along the lines you're thinking about and it may well work fine for you, but since you're planning to put down a laminate floor, I've heard of folks who have had success throwing down a vapor barrier (which you're going to want any way) and then a layer of plywood, shiming the plywood up to level with a selection of custom sliced sleepers. A selection of Two-By lumber and furring strips, some scribing tools, a jigsaw and belt sander ought to get you what you need. Lay the plywood "floor" so that it touches the concrete only at the higest spot and then the sleepers support the plywood over the lowspots. Construction adhesive on top of the sleeprs should keep them from wandering off. Then lay your laminate floor on that.

Free advice: worth every penny.

John

[RB]

I've leveled concrete floors using Quickrete's self leveling product. It works well but as was pointed out it is a bit pricey. Estimate the volume you'll need. If you're ok with the cost it's not a hard job. Mix 25 to 50 lbs at a time, I use a 1/2" drill driving a mixing paddle and pour it on. It will help to have one person mixing and another spreading and working the surface.

Make provisions to put a form at each floor level entrance or exit. Having self leveling concrete running out of a door can be a bit stressful.

My observation is that this product will not be as hard as the concrete you'll be covering though. Be sure to install a good vapor barrier before installing your flooring.

RB

D K Woods wrote:

[D K Woods]

Thanks for the tips! Fortunately, it's the entire basement area that need redoing, so if I just block the garage door I should be ok. I can imagine how that could get easily out of hand, though!

What I'm not sure about is how much Xlbs of resurfacer will surface. So, say that the average depth -- the troughs of the waves, so to speak

-- is 1/2", and I would guess the entire area to be roughly 750-800sqft, so the volume of resurfacer I would need is about 34 cubic feet (rounding up). About how many lbs of resurfacing mix would this need? (Although the quikrete website recommends patching the really deep spots with an acrylic fortifier/sand mix first, so that would probably dramatically cut down on the amount of mix I'll need.)

thanks

-david

RB wrote:

[D K Woods]

I hadn't though of this yet, it could be an option.

I'd like to know the full extent myself. I haven't peeked under the carpet yet, but assuming it's about the same as the unfinished portion, then I would say it's moderately flat with two or three really rough/wavy spots.

Ugh.

Good, those kind of fumes I can handle. I was more worried about some of the epoxy-based solutions I've heard about.

Thanks for the advice!

-david

[Jay Chan]

I did something like that just 4 to 5 months ago. My suggestions are:

- Check the basement head room. If the basement has a low ceiling already, you may not want to spend too much effort in converting it into a living space. A low ceiling will not be a very nice living space given the time and effort and money that you will spend on converting it. My basement has a low ceiling and I converted it anyway. If I could start this over with, I would not bother converting it. Moreover, if you raised the floor (in order to make the floor even) and then put in a drop ceiling, your basement head room will be even lower than it is now.

- Leveling the floor with leveling compound or concrete is no fun, is hard work (bad for your knees), is nothing to be proud of (I gain no credit by pointing at my floor and tell my friends: "I level it!"), is very easy to make mistake, and is next to impossible to undo the mistake, and is costly if making mistake. You are better off contracting this out. If I could do this over with, I would surely hire a pro to do that part of the job.

- At the minimum, you should postpone this until you have lived in your new house for a year or two. Then, you will see whether your basement really has no water problem or not. Watching it for one season is not enough in my opinion because the water can come from many places that may only come in a heavy rain storm. Moreover, after one or two years, you will have a much better idea of how you can use the space in the basement.

- Considering the time and money that you need to spend on fixing the basement and if the ceiling head is low, you may find that leaving the basement for storage may be a good idea. Or you can simply put rubber tiles over some area in the basement and use that area for doing exercise (put plastic sheet under the rubber tiles). I have seen very nicely done storage area in an unfinished basement in one of the Sunday Times Magazine. Or you can put your workshop there. You really don't have to finish it.

- The "self-leveling" property of leveling compound is much less than what you and I might have thought. It is "self-leveling" as being compared to concrete. It may work in a small area (like a small bathroom). But in a large area, you still need to help it along with tools.

- Leveling compound is very expensive. If your floor is so uneven, you need to even it somewhat with concrete before using the expensive leveling compound. Or better yet, you can use wood strips to level the floor if you don't mind losing the vertical space for the wood strips.

- Find the exact level line in your room using a laser leveler or a water-tube leveler and then transfer the level line to the floor level, instead of depending on the so-called self-leveling property of the leveling compound.

- Use a string to connect the leveling line that you have marked on the wall to find the high spots and low spots in your floor instead of depending on eye-balling.

- Mark the high spots in your floor, and never pour anything that will be above the high spots. This is easy to pour the concrete and leveling compound; but this is very difficult to remove them if you pour too much and they have become hardened.

Hope I have talked you out of doing this. Good luck with whatever that you will decide to do.

Jay Chan

[D K Woods]

Wow, Jay, thanks for the excellent comments! It is definately starting to sound like something to hire somebody to do.... The room in question is already finished -- just with a rather bumpy carpet! We're definately redoing the floors in the main and second levels, and while it would be nice to do the basement at the same time, between the comments I've received here and some financial hints from my wife (ahem) I think I'll be putting up with the basement as it is for the time being!

thanks again,

-david

Jay Chan wrote:

[raven]

Umm, AFAIK, this is untrue. Let it cure for a day or two and you could throw down a vapor barrier and go to town.

John

[Jay Chan]

I can see that your wife is a very smart woman and watches every penny :)

When you move into the new house, you may want to move stuff away from the basement wall. When it rains, you may want to go down to the basement to make sure you don't see any water near the basement wall. Meanwhile, start visualize how you will be using the basement, where to run ductwork for the central air conditioner if you don't already have one...

Good luck with your new house.

Jay Chan

[D K Woods]

Hi John,

Thanks for the second opinion. According to the Quikrete website the 'fast-settings' version should be good after 24 hours (and it even mentioned that you can walk on it after 6!). But I figured that must be a best-case-scenario for outdoors work. I'm sure being inside will slow down the curing -- but weeks sounded a bit much.

Of course, if Chris' goal was to frighten me away from the project, well consider the warning heeded. It's looking more and more like something that will be done sometime over the next few years instead of next few weeks.

-david

[Chris Lewis]

According to MLD :

Not necessarily. The vapor _may_ pop ceramic or vinyl right off the floor, cause mould in carpet/pad, cause hardwood to buckle.

Take a 2' square of heavy plastic (like dropcloth). Tape it down over the concrete and seal down all the edges.

Let it sit for several days (preferably in the spring). If you have condensation under the plastic, you will need to address the moisture problem.

This is one way to tell when a new floor treatment is okay to cover over.

[Chris Lewis]

Do realize that Quickrete's numbers are for setting of the material so that you can walk on it. Ordinary concrete achieves about 95% of its strength in a few days (less with quickset types), but the curing process continues for much longer. Ie: a month.

I'm referring to the amount of time you may need to wait before _finishing_ the floor, not how long you need to wait to walk on it.

Take a look at the instructions for painting concrete and you'll see what I mean.

Fresh concrete is often a difficult surface to paint/bond to. Due to the concrete itself (eg: base pH), and/or due to the the fact that concrete continues to outgas moisture for a fair while while it finishes off final cure.

The latter is _especially_ an issue with hardwood flooring.

The former is why you often have to use muriatic acid to prep concrete for painting.

I didn't mean to do that. It just sounded like you had a generally uneven (rather than spot-uneven) floor, where at least hearing what a couple of contractors who actually _saw_ your situation would suggest would help you decide what to do. If it's just a few square feet you need to level, that's a different ballgame.

My remarks about long wait times is meant in this way: you get the floor/spots releveled. You'll be able to _use_ the floor in a day or two at most. But I recommend waiting a month or more before putting a floor covering on it.

Two steps with a fair length of time between is simply what I suggest.

[MLD]

My comments reflect my own experience as well as others that have similar installations. I had carpet on the floor for years without any trace of moisture or mold; currently have ceramic tile now for 2 yrs again without any problems. Taping heavy plastic and sealing the edges would be a good test to determine just how bad the moisture problem would be if an installation used a vapor barrier. However, I don't think it is applicable to a floor covering that will allow the moisture to pass on through. On the ceramic tile installation I believe that it is the grout joints that allow the moisture to pass through. And, as previously noted, in my case, this is on a floor that developed bubbles of water under a *poured floor* which was essentially a vapor barrier deluxe MLD

[raven]

Even longer still: concrete never stops curing, but the amount of increased strength gets infintesimal after a while.

Painting is another matter and you're quite right: you probaly should wait a month for that. But laying a laminate floor atop the floor could be done as soon as it's safe to walk on.

Which is why you put down the vapor barrier, since you don't want the water evaporating for good strength of the concrete.

If you're talking paint or stain, I'd agree, but laminate flooring should be able to go down as soon as you can walk on it, provided you put down a good vapor barrier to isolate the moisture.

But then I wouldn't bother with a cement fix at all, I'd do it with lumber as I already suggested.

John

[D K Woods]

Ah, ok now I see where my lack of base knowledge comes in. This makes sense.

As for spot-uneven vs generally uneven...that will be a mystery until the carpet is up. It *feels* generally uneven, and the unfinished utility area is fairly wavey. As for the two steps with a good bit of time in between... Well, the area is already finished and will be the new home office (I work exclusively from home) when we move in. I was hoping the flooring good be done in the six weeks between closing and when our current lease is up. But I'll just wait a year or so, then move the office temporarily into the living room or guest room maybe while I give the floor plenty of time to set.

In any case, I admit I was getting a little ahead of myself. It would be nice to get that done before I move everything in, but I think I've talked my wife into putting some money into a really nice refridgerator instead. I can live with that.

-david