How do you fix a poorly laid slab?
DangerousHomeOwner
| Posted in Construction Techniques on
Through shared miscommunication and my ignorance, a mason has poured
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concrete slab in my row home basement that undulates and rolls.
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Fully cured in 28 days below grade!! NO WAY, maybe in a year. But it may be cured enough to use DAP 80P floor leveler with latex additive and enough additive to use as a brush on bonding agent. What ever you do now use a bonding agent to assure adhesion. I would not use a finer concrete I would use a portland cement base floor patch with latex such as webcrete 98 you can go from 3/4" to feather edge in one coat with this product and it has enough latex so you won't need a bonding agent. Are you sure you want to level or just fill in the low spots.
A lot depends on the quality of the concrete in the initial slab as far as what to put over it and when. If it was poured with a high water cement ratio (very wet mix and/or minimal cement content) you'll experience quite a bit of shrinkage as the slab cures. And yes, as was mentioned, below grade, the slab will take weeks to become close to cured.
If you pour a secondary lift of finer aggregate concrete on top of this it probably should be bonded to the initial slab. This means as the lower slab moves, shrinkage cracks will tellegraph through. A topping mix or leveling compound would do the same thing. If you plan to cover the floor with carpet, this isn't a concern. If you're planning to put tile, you'll need an anti-fracture membrane. Hardwood (designed to go on on-grade slabs, of course) require a different approach yet again but can be installed to isolate the flooring from the concrete to minimize or eiliminate the slab movement from the flooring material.
If the contractor thinks he/she can get the floor level with an additional lift of concrete, I think that would be my choice. But I'd get it in writing - the specification for flatness (usually something like 1/8" in to feet or whatever), some sort of warantee with respect to not having the skim coat dry and curl up like a bunch of potato chips and lastly, of course, some sort or reassurance that the skim coat will be bonded to the substrate. Yes, a bonding agent would be appropriate.
Dennis in Bellevue WA
[email protected]
I disagree on the curing of the slab. Concrete cures as a result of a chemical reaction inside the mix, and it requires a certain amount of water to do so. One problem with slabs poured in the open on hot days is that they can dry out too quickly, causing problems. This slab will be in a moist environment for quite a while, so it should cure nicely. I think what you meant to convey is that there will be a higher moistutre content in the room because it is essentially trapped, and the slab will feel damp and cool. It would help to get some ventilation in the basement, possibly by opening windows and stairwell doors and adding a fan.
Janet it's a little late now, but did he use any type of screed bars, or did he just pour the concrete and try to level it by eye?
If you have dips of 3 inches, it may be difficult to get a leveling compound that will fill those in one pour.
Do it right, or do it twice.
a one inch topper will not bond to slab and will not last. I really do not know how to fix but I would be moving into the area of grinding high with a commerical floor grinder and then using a self leveling epoxy grout like "five star" To top you will need a least three inches.
I question whether this contractor is capable of fixing the poor work he/she installed. Don't buckle to the time frame. Tell the contractor that you cannot make a decision immediately and that you will need some time to get some more information. Tell the contractor that "your brother"(or?) is going to look at it and you have to wait for that to happen. Ask your contractor to use this time to investigate other solutions.
Meanwhile, get another Concrete Contractor (or 2) to look at the problem. Stall long enough (on your answer) to get more info and make an informed decision.
Edited 7/2/2003 8:57:25 AM ET by GT_COLO
Many have posted good recommendations but I think that GT COLO made some really good points. If this guy is incompetent, then he will just make it worse. An existing patched floor will eventually show cracking at the placses where the old meets new. Another consern that MIGHT be an issue is you(and maybe he) probably don't know the ratio of aggregate to cement and other additives. If done incorrectly, you will have another nightmare on top of the existing. Plus, if your floor is out 2-3", then will an addition of another inch of float really make that much difference. Or, can you just float to even out the high/low spots and forget trying to make it level. Even will material used for self leveling that also had feathering capabilities, if it is not mixed right, you can have problems. Talk to another finisher or two, it might be worth the additional money spent. Out here, there are companies that specialize in this type of work, recoating existing slabs. And by having a basement, then I would assume that you are not in southern Calif.
I'm in agreemenmt that it doesn't sound like this "contractor" knew what he was doing so any advise he has about the fix is already suspect.
You mentioned it was partly from mis-communications that you ended up with a three inch roll. I'm having a hard time imagining how anyone - even a beginner, can make that bad a pour!
Leveling compounds for fresh work portland based, are available but not cheap. That is probably why he's trying to talk you into another whole float-over. There's a lot of bags and a lot of mixing to fill up to three inches. Once again, he's looking for the cheap and easy way out.
How much headroom will you be left with ? What is code for that in your area?
I'd might be considering getting that "contractor" a jackhammer to play with. It might be just the level of work he's capable of..
Excellence is its own reward!
Thanks to all who have weighed in. The more I think about and look at that pour, the more pissed I get.
We nixed the second pour because we already were tight on head room and didn't trust the guy to not make it worse. A jackhammer is definitely what's needed, but right now, the decision is to go with a leveling compound in 4+ weeks, using the original masonry contractor. In the meantime, the general contractor begins work on 1st floor renovations, and I may get some second opinions about the basement and weigh all the advice given here.
Any more advice out there? Thanks again.
JanetP
Let me weigh in on the side of a bad job. INcompentence or lack of caring or rip off???
As to the cure... the slab will be very nicely cured in 28 days under thase damp conditions.
But, it may be to wet to work over. At the very least, the top of the slab will have to be dry enough for the adhesive to set.
NO matter what you decide to do, you should get some air movement in there NOW.
I wish you lots of good luck and may your future be content.
SamTSleepless in Columbia. Diurnal rhythm? What songs did they do?
RE: water moisture in the slab. The contractor had the cement supply co. put a chemical in the mix to help it dry quickly. We could stand on it Tuesday after a Monday pour.
I had wondered whether the quick drying mix contributed to the uneven pour.
Windows are open on each side of the row home basement. Air is circulating. Would a residential grade fan in each room be needed?
Janet
Since in your initial post you indicated you were in an information gathering mode, I'll just mention from your last post .... the chemical used to hasten the setting of concrete, one of them at least, is calcium. It's called an accellerator. The last slab I worked on we added 1% calcium to the concrete. We started the pour at 11:00am and by 4:00 that afternoon we had a shined finish, power trowled and all and were walking on it! That was an exterior slab with partly sunny skies and a slight breeze all of which helped get the slab to kick off for us.
If your contractor was in the least bit inexperienced in concrete work and, most of all, under staffed for placing it, and ... if there was too much accellerator in the mud - I'm surprised you don't have a pile of hard concrete in your basement! (just kidding)
I think your decision to take the whole thing out and start over is the best idea. But! Don't wait the 28 days!! Get it out this afternoon or sooner. The longer it sets the harder it will be to break up.
I forget - did you mention how big an area you're dealing with?
...........
Dennis in Bellevue WA
[email protected]
14 x 23 ft. main room of a row home basement
We'd like to pull the concrete out and start overagain, but don't know how to negotiate it and are concerned about the schedule for other renovations going on in the house. (We are in a sublet and already know our sublet is going to be up before the renovations are complete--even without this problem)
We still owe the contractor $3K. He is concerned about his reputation. our current agreement with him calls for him to use hte leveling compound on the slab a month from now.
If we were to negotiate removing the first slab and starting over again, I thought it would be fair if we paid for the disposal fees and MAYBE the gravel used for setting up the new bed. He'd have to pay for all labor, and concrete used in the second pour.
Does this sound fair?
Janet,
Right now I picture a concrete floor made up of new and old patchwork, all on the same basic plane. In other words, you cut out sections of the original floor and changed the plumbing, filled in the opennings to the underside of the old concrete and poured concrete "between" the old concrete floor opennings.
If this is the case then the odds are regardless of the use of either a topping or a leveling scenerio, it will be prone to fail.
If I'm wrong and after he filled the trenches with gravel or whatever, up to the same level as the old concrete and then poures a thin slab "over it all", it will be prone to fail.
Yes an error was made in not removing the entire slab and working from scratch.
Now you have a problem, so the next step is to find the most cost effective solution that you can live with.
You can scarify the high points and then use a "thin" layer of epoxy topping to smooth it to an acceptable level.
This can be done in a day to scarify and another for the epoxy to dry and you're back on some semblance of a schedule.
Gabe
You still owe $3k on 322 sf of slab? That's $10/sf. How much was the original cost, and is it for more than just the slab?
If you plan on taking it out or grinding the high spots, start work now while the concrete is still green. If you are going to leave it in place and top it later, then you can put your attention to something else. As to negotiating the removal...the only thing for you to give up is time.. Unless you gave specific instructions to him as to how to place the new slab, it's all his. Hopefully you said something like "I want a nice level slab in the basement, minimum 4" thick, what will it cost?" and left him to make the means and methods decisions.
Do it right, or do it twice.
Janet, you've gotten some great pieces of advice here so far, but the cynical side of me is still puzzeling over a couple of details, if you don't mind me asking...
You mentioned that you have a sub-lease. Now, I'm not a city dweller but to me that implies that you do not own the building and don't even have a direct relationshiop with the owner. If that is so, how do you have any right or permission to be doing this work? Is it covered in the lease somehow?
Here's where I'm going with this line of thought -
If I owned a property and rented it out, and then found out after the tenants moved, that they had done major renovation work to my property, I might or might not be pleased. If the workmanship were poor, as you have described, I might be hopping mad, especially if it was going to cost me mucho dinero to remove and replace that work. I might even be mad enough to sue the person(s) responsible for causing the situation to exist for the cost of repair and replacement.
If that is similar to your scenario, you will want to do as suggested above and lay it all back in the contractor's lap.
Now then - the other thing you mentioned is something about the presence of a General Contractor. If there indeed exists such a person, he should be the one responsible for overseeing the concrete work and for forcing the concrete subcontractor to fix it without cost to you.
But I confuse myself here. In my area, it is not possible to get a permit for work without some form of authorizatrion or power of attorney from the owner of the property. it's a sensible thing intended to keep shaggy contractors from practicing building a house on my property or stopping me from building a fence on my neighbors property to hide their mess. So where I confuse myself is in wondering how you got a building permit when you seem to have no relationship with your landlord. Surely your general contractor has a license and is working under some sort of permit????????????!!!!!!
Or am I out to lunch?.
Excellence is its own reward!
Piff, I think they are in a rental house or apoartment, and the lease will expire before the new place is ready. Good points though.
Do it right, or do it twice.
OK Maybe I read that part wrong, but still, if there is a general, she shouldn't have to be sweating this problem. All she needs to be doing is to say, "That's not acceptable work. Have it fixed right before we pay for it."
She shouldn't have to say another word.
It's the job of the general contractor to provide her with acceptable work, regardless of how he does it, she shouldn't be worried with it..
Excellence is its own reward!
To fill in details for those helping me puzzle out this issue.
The general contractor is not involved with the basement work. We opted to coordinate the lead tile removal and the masonry work--learn as we go, at our peril, apparently. How hard can re-stuccoing some walls and pouring a concrete floor be?
We were planning the 1st FL renovations, already had a bid, when we tested for lead and discovered the presence of lead in the tile laid hapazardly on the basement floor and walls. Normally this wouldn't be a problem but the bsmt floor tile was cracked, its glaze compromised and the basement floor tested high for lead dust. Living with it, with a toddler, was not an option, so we decided to take it out--lead removal contractor and all.
The 1st floor renovations and the basement work are being done under one permit, which I applied for.
Electrician, whom I am running, and plumber, whom my contractor is running, are applying for their own permits.
now I'm going back to re-read the advice.
thx to all.
j.
Things become more clear to me now. Thanks for the reply..
Excellence is its own reward!
Hello. DonP, husband of JanetP here, trying to summarize in my own mind what has happened and what I have read so far.
While our inexperience and possible lack of communication are hard to deny, I don't think they can be blamed for the quality of the original pour. If we had gotten, say, a broom finish when we wanted a screed finish, I could attribute that to miscommunication. But I think it goes without saying that we didn't want our basement floor to look like a skate park, regardless of what our future plans were.
I realize that the ideal thing would have been to stop the job until the situation was made right, but we are living in a time-limited sublet appartment, and paying rent for that as well as for storage of our furniture etc. Added to the stress of not living in our own house, that places significant pressure on us to get the other aspects of this project complete.
I now realize that fixing the current slab without removing it would be risky even with a highly skilled contractor, and based on his first try, I'm not confident that the first guy is up to it. I also seriously doubt that he'd be willing to tear it out and try again without a fight. And even then I would still have doubts about his abilities to pour it a second time.
OK. I've now convinced myself of how I'd like to approach this, but I'm still open to comments. We negotiate with the current contractor based on our withheld funds to "terminate for convenience", either right now, or after he has removed the faulty pour. We then hire a different, skilled contractor to install a new floor from scratch, even if that costs us a few thousand dollars more. I suspect that will require another permit, however.
Sheesh...
-- Don P. --
Unless he holds the permit in his name, I don't see the need for another, though many jurisdictions have some strange rules. It would seem to me that you have a permit to install a concrete floor, it shouldn't matter how many times it takes to get it right.
I could have that slab broken up with a jackhammer in less than two days, unless there is a lot of old harder cured stuff setting under it still. Removal of debris is something else though, depending on how it has to go out. That could take significantly longer. It might be possible to do it all for three grand. That puts you back at square one.
Remember to get the place retested for lead before moving back in..
Excellence is its own reward!
DonP, do you have your wife's permission to hijack this discussion? She was doing just fine all by her self.
I don't think anyone here was laying any blame on Janet or her assistant for the problems with the floor. One thing you need to keep in mind is that no one here has anything to gain by criticizing another contractors work. Unlike another local contractor who wants the job, all we do is pass judgement on the "facts" as presented, and tell you what we would expect to be a fair resolution. Then it's up to you to adapt our comment to the local situation, and make a decision.
Here's a thought...since the lead removal is complete, can you continue with the rest of the project so you can move back in, then resolve the basement floor as a separate project?
Do it right, or do it twice.
My husband has never met a message board thread he didn't like; not surprised he weighed in in force.
We're going to try to figure out the costs of re-doing the job: removing the new and old concrete, laying down a bed of gravel and pouring new. Then we're going to go back to the original contractor to negotiate a better fix than the leveling compound patch.
What's the ideal depth for a row home basement slab, about 6-7 feet below street level in Philadelphia's climate: 4-inches, 5 inches?
And how deep should the gravel be: 2+ inches?
Do we need a vapor barrier for our Philadelphia row home basement?
(I've been reading....)
What else am I missing? Was thinking about calling the local trash transfer station about disposal costs.
All I want is a nice LEVEL concrete basement floor--what could be simpler?
I didn't take Dons comments as heavy at all. He's used to making decisions and able to be straightforward. I can work for/with him.
The amount of gravel needed is a function of water and soils conditions there. It serves a couple of purposes. It gives water a draingae space to follow instaed of rising above the slab. It provides something easy to rake level and grade. It is a solid material to give a good base for the crete.
So if you have wet clay mud, you need a foot or more of gravel. If you are down to hardpan, you hardly need any.
When you break up the concrete there will be a lot of cookie crumbs that can be used just like washed stone in there and you may not need to add any gravel.
IMO, Any slab under living space always needs a vapour bar..
Excellence is its own reward!
JanetP, I feel for ya, I really do. I do believe all persons should be involved in one remodel, addition or new construction project before they die. As you asked in your last post, ie a flat slab, how hard can that be?? Whenever there is money involved, (usually the HO's), and some aspects of the job go south, then I wish all involved, clear, open communication, and sometimes compromise. My own gut feeling on this one, you want a flat slab, then jackhammer this one out, start over, pour a new 3 1/2" to 4" thick slab , with a new concrete co./ finisher. As time passes, evertime you are in the basement, you will hopefully get that warm fuzzy feeling, note; as time passes. I wish you well Jim J
What's the ideal depth for a row home basement slab, about 6-7 feet below street level in Philadelphia's climate: 4-inches, 5 inches? Thick enough to hide the bodies...Do it right, or do it twice.
The Ideal depth for a basement is, the basement should not be any deeper then the high water table for the piece of land of where the house is. In some places that may be only 3 ft into the ground. So if you need to go deeper it is more important to a plan for dealing with the water. Like good water proofing, bigger drain tiles, bigger sump pump Another way is to hauling in more fill and grade around the house taper way from the house.
Unless you don’t mind water in basement.
I didn't mean to imply that anyone here was blaming my wife for the condition of the slab. Although I now see that it is not clear from my original post, I was responding to something the original contractor had said about miscommunication.
As always, however, it's not a one-sided issue. We should have been better-educated and had the old floor completely excavated. That would have increased the likelyhood of a nicer finished floor. At the same time, even the poor substrate does not fully explain the surface we ultimately ended up with. I'm only exagerating slightly when I say it looks like these guys smoothed the floor with the backs of their shovels.
So, as my wife said - this is her project after all, we are going to get competitive bids and then negotiate with the original contractor to decide how to split the costs. We'll probably also offer him first right of refusal on the re-bid as well.
Thanks again for all your input.
-- Don P. --
I was just giving you a hard time about butting in on her discussion. You may be required to give the original contractor the option to fix the floor...I have not followed it closely, but there is legislatiuon existing and proposed in some states that give the contractor the right to cure the fault before the HO takes action. That said, I would have a hard time splitting the cost with him.
Do it right, or do it twice.
Piffin,
I'm not that crazy. I own the property in question--the one with the poorly laid slab in the basement. I'm subletting an small apartment, so that my husband, toddler and self don't live amid the basement and 1st floor renovations.
wanted to respond to that issue. have to read everything else.
j,