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RDS 05-28-2008 11:47 AM

How to level small patch of cured concrete?
Not sure which forum is best for this question, but here goes.

I need to replace a post lantern in my front garden. The current one, which I'm discarding, is screwed into a round concrete base about a foot in diameter. I want to reuse the existing base for the new lantern.

Problem is, it's not quite level. I have reason to believe it goes about two feet into the ground (I had to dig out another one in the back yard) but over the years it's settled slightly, with the result that the existing lantern is not plumb. Maybe 15% off.

I really, REALLY don't want to dig it out and repour it. (A) It'd be a lot of very hard work and (B) I'd end up wrecking the garden that it's in. If I can reuse it, I'm willing to gamble that it won't shift or settle any more. It's been in there probably 40 years.

So how can I level it? Can I grind it down? I have a 4.5" grinder, but the concrete grinding wheels I saw at HD sell for upwards of $100. Could I just use a masonry cutting wheel and sort of chip out pieces until it's level? (No doubt the result would be less pretty, but the disk is cheaper and I could cover the base with garden mulch.) Or is there a way to *add* a little bit of concrete or other material to bring the low side up to level? Obviously it would need to bond with the existing concrete.

Or am I overthinking this, and there's some easy way to shim underneath the lantern to make it securely plumb?

Basically I'm wondering whether anyone else has tackled a similar problem and come up with an easy and effective solution. Thanks for insights.

RDS 05-28-2008 12:31 PM

Sorry, I meant 15 degrees off plumb, not 15%.

werc 05-28-2008 05:57 PM

Last year we had a community mail box installed by a cement contractor. The box had to be installed on a 3 x 3 cement pad. The location was on a hill. I had assumed they would poor the cement level, then mount the post to the mailbox. To my suprise, they poored the pad to match the grade of the hill, then used shims under the mail box post to make it level. I have never looked real close, but the shims are metal, and the connecting bolts passed through them to hold in place. In your situation, perhaps washers would do the trick. I would definitely go that route before any attempts to modify the existing cement pad.

clasact 06-04-2008 08:28 PM

I was going to make a suggestion on how you could get this level but then I notice where you were from.My ideal would have left you with a cold joint that probibly would not hold up to well after a winter or two better go with the shim ideal

Termite 06-04-2008 08:58 PM

There are some nifty concrete topping products available such as quickrete. Normally I'd advise against a cold joint but this is just a lamp post and doesn't need to hold water out or resist hydrostatic pressure. I'd suggest screwing a few tapcon screws into the existing concrete and letting them stick out an inch or so, just to act like rebar to tie the old concrete to the new. If needed, you can build a level form on top of the existing concrete. Just try not to get any wider than the existing concrete...Any overhangs will give the earth something to push up on when the ground freezes and heaves.

RDS 06-05-2008 09:22 AM

Thanks for the suggestions, all. Not sure which approach I'll take (haven't actually bought the lantern yet) but this gives me several options to chew over. Gracias.

clasact 06-05-2008 09:42 AM

RDS the suggestion I was going to make but didnt due to the climate it would be exposed to was to get or make your own sono tube to fit over what you have get it level and pour new cement and stick some lags or whatever in it for reinforcement.You could also put your mounting bolts right in the new concret.I did not think this would work due to the extrem climate change in your area( I have been their I am right off I-80 myself) but if KCtermite thinks it will be ok on the cold joint then I would say give it a shot

Termite 06-05-2008 09:45 AM

Yeah, if it were anything else I'd say avoid the cold joint. For slabs, walls, and footings it is not adviseable. But, I don't think that there would ever be an issue with a light pole base as long as the two pieces were tied together with tapcons or lags of some sort.

RDS 06-05-2008 09:51 AM

You know, I may try that. What's the worst that could happen? If the bond doesn't hold and the new concrete shears off, I'm back to using shims, which is certainly an appealing option for its simplicity although I do think a leveled base with new concrete would look a little better.

Termite 06-05-2008 11:19 AM

Just do like I said and install a few tapcons in the old concrete, and leave them sticking up. They'll give the new concrete something to bond around, even if the old and new concrete don't bond very well.

skymaster 06-05-2008 11:57 AM

RDS where 'bouts?

Tscarborough 06-05-2008 12:41 PM

Leave it as is, put the new lantern on it, shim it level and pack with non-shrink grout. That is the proper way.

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