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I need to raise and support a concrete slab that has been settling for the last 8-10 years. Add to the mix a wall that supports the roof of a carport, sitting on the edge of the slab, and an owner who doesn’t want to tear it all out and start from scratch
HELP!
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Replies
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B. - I just looked at a similar job this morning. I don't think mines settling yet, but the back side of the garage slab is undermined. I think it never was on compacted soil as it sits on a slight slope. I am thinking we'll have to excavate and pour supporting walls in sections so as to not excavate under the whole length of the building at once.
Have you considered cutting the slab in two (or three) so you are dealing with a smaller piece(s)?
Even if you can lift it, how will you backfill under it? Seems like a tough proposition. - jb
*The only thing I know about this topic is that in my area there is a company called something like A-1 concrete leveling.They inject some kindd of concrete mix under the slab and it lifts it back up to level,or approx. level.I have seen this done several times with pretty good results but I have no idea about the long term results,or costs involved.Looked at a chimney the other day that had been added long after the house was built. The foundation for the chimney settled away from the house so that the chimney pulled away from the side wall about 1/8" at ground and about 4" at roof line.Makes me wonder if these guys could straighten THAT out?Just an idea,Good Luck,Stephen
*this will require the attention of an engineer to to the job properly. It probably would be cheaper to rp it out and start again. Sounds like it needs underpinning of some kind ( there have been some articles in FHB on this ) and screw in piers may be an alternative....cover your butt and see the engineer.
*Hey mark, man, you're absolutely right! Not too long ago there was an article about jacking up broken foundations. Used those kinda auger lookin' things to lift with. How would a guy find that article without going through old issues? - jb
*Hi B. RyanSure is fun when the owners expect you to fix something that should be demolished and built right.It, doubtful that pressure grouting would be able to lift your slab. Pressure grouting is best when the grout has no where to go but up. In your case it will simply slip out the sides.The best alternative is to brace the roof and wall sections in order to support them off the slab. If the slab has sunk, so has the wall and roof.Take a concrete saw and cut along the inside of the wall, about 1 foot inside the garage. Then you remove all the material under the lenght of the wall and down to solid undisturbed soil and below frost. Form the outside of the footer, fill with concrete to the proper elevation to hold the wall section.Remove the bracing and set the wall onto the footer and pin it in with quickbolts.The slab can be added to afterwards with a capping of peastone concrete with a latex adhesive over the old slab. (still would be better to remove)Gabe
*Remove the columns supporting the carport roof. brace carport roof with something else that rests off the slab. fix the slab.Now if you need to also know how to fix the slab you might not even want to take on the job but I would agree with the method of leveling with pumped grout. any other means will never give you a long lasting leveled slab.ONE MORE THING...be sure to dtermine what is causing the sinking. is the slab on a higher area of ground than the surrounding area and dirt is washing out? is ther water flowing under slab via cracks or otherwise? is there a drain crck nearby that may be cracked and is sucking away dirt beneath the slab? Fix the prob first.If the customer wants a half ass fix then refer him to the neighborhood handyman (assuming that you are not the neighborhood handyman.)Pete
*Ok guys don't kill the grout pumping idea first. I had a lot of luck in fixing slabs with grout pumping. I'll need some more info on your slab to offer a fix1 How much has it settled? (1/2?...6"?)2 How many cracks and how big? ( small hair line cracks? 1/4 cracks? )3 Site area?/ Soil type? (level, rolling mountain side?) You may have to replace the slab or you could retop the slab
*One of the TV shows (Bob, Norm and Jim, Dean and what's her name this week???????) showed that process. I think there's a presumption that an engineer (their's or your's?) has determined that more structural underpinning or repair is not required. Apparently not cheap but maybe cheaper than tearing down and starting over. Apparently best for slabs (as opposed to walls or point loads) as the pressurized material lifts against a large surface area and pressure is maintained by keeping the material there.