Cracked Slabs - Bad As They Sound?
I've always been under the impression that a cracked slab was a bad deal and a 40 - 50K (or more) fix. A contractor once told me that they were no big deal, but he may have just been blowing smoke. Any info on cracked slabs, fixing them, disclosure after repair, etc.? Thanks in advance!
-e-
econrad,
What concrete slabs are you talking about? Driveway? Foundation? SFR's, Commercial? What's the square footage? Is it reinforced... post stress... ????
You would need to be more specific for us to help you better.
Sorry 'bout that. There's not a slab in particular - I was just thinking about a conversation a while back, and in the past how I steered clear of them. The most likely scenario would be a foundation on an SFR - that would probably not be considered a cracked slab, technically. I'm not sure what you mean by post-stress or reinforced (maybe rebar-reinforced?). Sorry about the newbie questions.
-e-
most monolithic pours and signle family slabs are cracked in my part of the country. This is no big deal unless the part that is cracked lifts significantly and causes a large hump in the floor.
I have reparied many of these and none for 50K. Generally an easy fix depending on the location of the problem. Generally you roll back the carpet, mark the area to be removed, scroe with diamond blade and jsackhammer out. Then you drill and pin with rebar and repour and replace the carpet.
WHen you come up against this it is best to get a bid from an honest contractor.
When people ask me about concrete, I guarantee them one thing...........that it will crack.
Its just a matter of where, when and to what extent.
Cracks occur for various reason, but mostly from shrinkage and stress.
Control and expansion joints help, however they are not full proof.
Unless the crack is uneven, gapping or extending from a load point, then usually one should not worry about it.
With that said, cracks should be filled so as to not let the infiltration of moisture.
If you suspect that this is a structural crack, then consult with an engineer.
NC
I agree with NY Yank if you pour Concrete it will crack. I once asked a good friend who is a contractor how to keep concrete from cracking he said don't pour it LOL
I live in a home with a slab and there are a few spots it has cracked a nice rug here and there and no one is the wiser. BTW it does not affect the value at all.
Concrete will rarely crack if certain measured are adhered to, and if so, minor to say the least without repair necessary. Granted geographical location will determine that design but generally speaking:
The base or foundation is properly designed to permit a even pour in thickness and prepared, expansion and contraction is controlled, reinforcent is installed, and , a very important measure that is always overlooked, even by architects for some unknown reason,is the CONFIGURATION. Concrete poured in exact square configuartions are less apt to fail then those of their counterparts. A 6' x 6' pad would be 36 sq ft. A 18' x 2' pad would also be 36 sq ft. The 18' x 2' pad although being the same surface area will most certaintly fail. Once you increasingly travel away from the safety of square, concrete travels increasingly toward failure. Now it is understood that square shapes are not always possible, one reason reinforcent came into play to aid in the stresses of the material by naturally faulted but accepted designs through configurations. Now this may sound contradictory but concrete is in fact induced to fail by design proving the Roman square theory. The installation of controlled joints in sidewalks to name one are cut to induce and weaken the concrete to crack at the most likely place that being the square juncture. Expansion jonts are installed at approx. 16 ft intervals per 4 ft. wide and 20 ft per 5 ft wide. All being mulitples of squares.
Dan
NY_Yank and Dan are right. I have placed a lot of mud. It is a parishable product and many thing can happen, not only in the design but the installation and finishing. There have been times when concrete slabs, footings or walls looked kinda sketchy, but when we went to jackhammer them out, they were insanely hard... ended up taking it out as gravel. Sometimes what looks like a nasty crack is just a surface crack. Other times I have had to repair very thin hairline cracks in perimeter foundation walls and the engineers wouldn't risk potential failure. The engineers solution was to have an epoxy injection subcontractor make repairs. It is amazing how well it works in the right situations. Sometimes you have to do what Stock pro describes... not fun. I'd add, that patches adhere better to chiped out surfaces rather than smooth sawcut surfaces. Unless you have a specific condition, I could write a book on how to repair every type of failure.
Thanks to all - I was just curious if I came across something with a foundation issue, if I should immediately write it off, or consider hiring an engineer / contractor of some sort to look into it.
-e-
Try to get a concrete truck driver to deliver concrete to a foundation job at a 4" slump. It wont happen. In their mind that means that they will have to move the truck in order to "place" (not pour) the entire foundation, slab or whatever. When concrete is delivered at a 8" slump it is a lot easyer to float, but because of all of that extra water you will have shrinkage cracks (unless a superplasticiser has been used). Small cracks themselves should not pose a problem to the integrity of the structure.
danc49, that was very informative to me, so thank you. Would you now, please, explain to me the "law of squares"? Haha, just kidding. I learnt something tonight! Z
Wow, that was interesting and very helpful. I wish I'd read this before I turned down a SFR with a crack in the foundation for 40% under FMV.
What inexperienced RE investor needs to know about the foundation cracks, specially in So CA where there is commonly no basement, is that they are fairly easy manageable and good reason for you to ask and get substantial discount.
Quote:
On 2004-02-21 21:43, JohnNH wrote:
Try to get a concrete truck driver to deliver concrete to a foundation job at a 4" slump. It wont happen. In their mind that means that they will have to move the truck in order to "place" (not pour) the entire foundation, slab or whatever. When concrete is delivered at a 8" slump it is a lot easyer to float, .....
My concrete supplier delivers 4 & 5 slump all day long.....if they sent me an 8, I would laugh and tell them to send it back or be prepared to give me core samples of 2500 - 3000 psi ...........during the next 28 days.........Im sure the laborers love working with an 8.
Bottom line, any substancial size slab of concrete, such as the slab of a house or driveway will crack.....no matter what....its just how you control WHERE it will crack.
NC
We do not even use 3000 psi crete anymore and have not used 2500 for the past 15 yrs other than K - crete to pump filler under settled Storage tanks. 3500 AE and 4000 AE is standard @ 28 days for us as drawn.
We have found the base compaction rate of 95% proctor with a crushed stone base also compacted and re-inforced with no.4 bar @ 12 " O.C. with a 6" 3500 psi pour on a standard residential pad will provide years of trouble free service. We have poured sections of route 95 in 1968 that is still intact except for surface wear. Mnay concrete problems are the result of preparation and proper installation.
Dan
Quote:
On 2004-02-24 01:35, danc49 wrote:
..............We have poured sections of route 95 in 1968 that is still intact except for surface wear. Mnay concrete problems are the result of preparation and proper installation.
Dan
When I lived in Cincinnati (for my confederate friends...it was not my fault as to the place of my conception...I had no say so in the matter....) and while traveling daily on I-75......I was amazed at how they could take a 5 - 10 year project and accomplish nothing........the concrete was in as bad as shape as when they first started.
My solution.........move south and enjoy asphalt and warmer weather.
Regards.....
NC
I think that location is the big factor, PA isn't Oregon or Texas, or Helena MT (where I poured two months ago) COncret will crack.. I put schedule 60 in 2'x2' grid everything, use 5.5-6 sack with fiber mesh added and as dry as I can work it and still have the occasional crack (not as many as the competitors
We have 60 degree changes in a day here, -20 to 40 degrees is not unheard of and 105 in the summer and snow in the AM.
I do not just mess with mud so I am hardly an expert in the esoterics but generally speaking, mud cracks and us not usually hard to repair
[/quote]NC_Yank
My concrete supplier delivers 4 & 5 slump all day long.....if they sent me an 8, I would laugh and tell them to send it back or be prepared to give me core samples of 2500 - 3000 psi ...........during the next 28 days.........Im sure the laborers love working with an 8.
[/quote]
NC_ Yank When your an established account and do a high volume of work through a supplier you MAY be able with send away a truck depending on your market. I have been at jobs and overheard dispatchers say to drivers via Radio "then tell him we will be back next Tuesday with a 5 caus we dont have time to F*** around"
Try explaining to a driver water/cement ratio
A lot of the big Union Companies are so big they act as though they are doing you a favor by making a delivery. The days of mom & pop concrete plants are coming to a close. I will take cylinders though instead of cores, I dont want the slab to look like swiss cheese. I have seen a 9" slump achieve over 4k PSI but that doesnt mean it wont crack.
JohnNH
[ Edited by JohnNH on Date 02/29/2004 ]