Can I level concrete footings?

September 4, 2010 10:54 AM

Uneven concrete footings for a deck - can they be leveled somehow or do I need to re-dig?

Hi,

I poured a couple of concrete footings (8- and 10-inch diameter) for an outdoor deck, that go about 4 feet deep. I did the work in a rush and now I am regretting it!

The tops of the footings (where the wood posts will sit) are not level (and I mean really not level) and it seems I am left with a couple of options (other than redigging)

1 - Cut the tops of the wood 4 x 4s at an angle so that while the posts itself are not plumb, the tops of the posts will be level to allow the beams to rest on them properly.
I don't like this idea so much because the posts itself will not be plumb, and I assume this will affect their ability to support the deck.

2- Somehow, level the tops of the concrete footings - I guess I can either:
- "Cover" the current footings with wider tubes (i.e. 12 inch diameter) and then fill those with concrete and ensure that these are level - I don't know if this is a good idea because these wider forms would just be sitting on the ground and would not be deep underground like the original forms
- "Stack" the current footings with a narrower tube (i.e. 6 inch diameter) and then fill those with concrete and ensure that these are level - In this case will the new wet concrete properly stick to the dry concrete?
- "Stack" the current footings with a tube of the same width and then fill those with concrete and ensure that these are level - In this case will the new wet concrete properly stick to the dry concrete?
Do you think that any of these options are feasabile? Are there any other fixes that you would suggest or should I just bite the bullet and re-dig?

I thought about self-leveling compound, but I read that this is for indoor use only, so I guess this is not an option...

Thanks for your help!

posted by bitteroldman to home & garden (14 answers total)

Grinding or cutting the footers so they are level where the posts attach? You normally have to do a bit of that anyway.
posted by fshgrl at 11:15 AM on September 4, 2010

Rent a hammer drill so you can install a metal post anchor with epoxy. Something like this. You could possibly crack the footing though, so be careful. Easier would be to rent a concrete saw and cut their tops off square and level. Get one with a water spray hose (dust control) if you can.
posted by bonobothegreat at 11:37 AM on September 4, 2010

"Cut the tops of the wood 4 x 4s at an angle so that while the posts itself are not plumb, the tops of the posts will be level to allow the beams to rest on them properly.
I don't like this idea so much because the posts itself will not be plumb, and I assume this will affect their ability to support the deck."

Right approach; wrong end of the post. Drill a hole in the top of the footing and insert a foundation bolt. You can do this with quickset or with a friction bolt made for this application. Cut off the bottom of the post and them bore a hole in it to receive the bolt. If you have set post hardware into the concrete, all you need to do is cut off the bottoms of the posts and secure them to the metal sticking out of the concrete. If not, when you do this fix, use a larger post, say a 6x6 instead of a 4x4 to give a little more "meat" to the support. Brace the posts against overturning until the deck is complete and them cross-brace the final structure.
posted by Old Geezer at 11:44 AM on September 4, 2010 [1 favorite]

I'm an architect and work with a design build firm. I'm a little unclear as to your existing situation. Are the tops of your footings well below existing grade? Are your posts currently buried and resting on top of these footings? If the tops of your existing footings are below grade, they shouldn't be.

The top of the footing should be just above grade (in a deck situation; houses and additions have other requirements). This keeps the bottom ends of the posts from being buried. The posts will fail if buried...even if they are pressure treated or cedar. Here's what I would suggest for adding to the top of your current footings. Dig down to expose the top. Clean the top and then clean it with some muriatic acid (available at Home Depot). Rent a rotohammer and drill (3) 5/8" holes in the top of the existing footings. Make these about 6-8" deep. Epoxy one 12" length of 1/2" rebar into each hole. Use Simpson Epoxy that you can also get at Home Depot. Set whatever length of new form (you are probably using sonotube?) over the top of the existing forms. If you use the same diameter, you can slide the new form down over the existing footing to help place it and keep the bottom of it stable. Pour the new concrete into these with level tops. The rebar holds the two pourings together and keeps the new pour from shifting on the old pour.

Connect your posts to the form via a Simpson PB44 or similar. This is a post base anchor that you set into the new concrete that will accept your posts with bolts instead of burying them. If you need to set these slightly off-center on the new footings in order to keep your posts aligned, that's fine. Just don't have them too close to the edge.

This should provide good connection of your two concrete pours, allow you to plumb/level your posts, provide good post/footing connection, and keep the bottom of your posts out of the soil. Good luck.
posted by nickjadlowe at 11:49 AM on September 4, 2010 [2 favorites]

Hi all, thanks for your answers so far! Here are some comments/answers to the questions you asked to help clarify things:

bonobothegreat and Old Geezer:
I have actually tried to attach metal post anchors to the footings (similar to this - they hold with a J-bolt which I embedded into the concrete when it was wet). But when placed, these anchors are also not level, so when I place the wood 4x4s on them, the posts still rise up at a slant (to the point where they tilt over).

A concrete saw might be interesting, but since I have the J-bolt inside already, I wouldn't probably be able to make a clean cut.

nickjadlowe:
The tops of the footings are about 3-4 inches above grade, so I guess I am OK with that.
I also inserted J-bolts (foundation bolts) into the concrete. But I guess the procedure to drill 3 holes and rebar to hold the two pourings together would still apply, right? What's the best way to use the epoxy - add the rebar and then fill the gaps with the epoxy? Are the post anchors that I have already (this - also made by Simpson) just as good as the PB44s? And I guess I would bury the existing J-bolts and have to insert new ones, right?
posted by bitteroldman at 12:27 PM on September 4, 2010

can you put a picture up?
posted by dripped at 12:38 PM on September 4, 2010

Is it possible that the J-bolt you embedded in the footings did not set perfectly vertical? I think that might be your problem, not that the tops of the footers have some slant to them (unless it's dramatic). In that case I think nickjadlowe's suggestion is going to be the easiest.

I recently helped a friend install a deck and we had to grind some high spots off a couple of the footers to get the hardware to sit absolutely flat but we're talking 1/8" or so and the bolts were straight so once the plate was able to sit down on the footer evenly the posts were also even.
posted by fshgrl at 1:34 PM on September 4, 2010

If your footings are already above grade, then you dont need to add an additional poured footing on top of it. I would do the following:

Don't worry about the top surface of your extsting footing. Cut the existing J-Bolt off flush with the top of the footing. Since this is at a weird angle, you won't use this anymore. Drill a new 3/4" hole in the top of the footing about 6" deep. You are then going to epoxy a new piece of 5/8" threaded rod into that hole (be sure to blow the dust out of the hole first or the epoxy wont adhere right). The threaded rod is also sometimes called "all-thread." You will find it at Home Depot or similar. Here's the important part...make sure you drill the hole and put the threaded rod in plumb.

You put the epoxy in the hole first and then push the rod down into it. The excess epoxy will ooze out of the hole. That's fine, just scrape away if there is too much of it. You just need enough to fill the hole around the rod. After it cures fully (overnight), screw a nut as far down towards the footing as you can. Next, slide your post base down over the rod onto the top of the bolt. Now screw another nut down over the anchor to bolt it into place. Your post base will not be at an angle to the top of your footing, but it should be plumb.

Now fill in the area between the bottom of the post base and the top of the footing with a structural concrete grout. You should find that at any masonry supply place. Something like this. Wait for it to cure according to instructions. Trim (saw) off excess threaded rod with a sawzall (or hacksaw). Drill a hole in the bottom of your post so the post fits over any part of the rod/nut that is sticking above the top of the post anchor. Make sure the post sits firmly on your post base.

That should be it.
posted by nickjadlowe at 1:36 PM on September 4, 2010 [1 favorite]

It may depend on the way the anchor flanges are oriented with respect to the slope of the footing. If the flanges run up and down the slope, you don't need to do anything. Just cut the bottom of the posts at the same angle as the slope so that they will stand vertically. If the flanges run across the slope, take out the post and just bend the flanges with a hammer until they are vertical. Then cut the bottom of the post to match the slope so that it stands vertically. If the flanges are at some odd angle to the slope you may be able to do some combination of the two.
posted by JackFlash at 2:17 PM on September 4, 2010 [1 favorite]

dripped:
I was going to try, but I can't get a good shot, nor can I hold the camera straight!

fshgirl:
The non-vertical j-bolt is the least of my problems! The tops of the footings are really slanted such that when you just sit the anchor hardware on the top, the hardware itself slants - the j-bolt doesn't really contribute to this

JackFlash and Old Geezer:
Interesting idea to cut the posts at the bottom end - the base will be angled, but flush with the anchor and plumb. I wonder if there is any downside to this compared to nickjadlowe's suggestion.

nickjadlowe:
I will try this suggestion first - Are there any structural advantages to using the concrete grout to level the uneven parts of the footing versus cutting the bottom of the posts at an angle as suggested by JackFlash and Old Geezer?
posted by bitteroldman at 2:55 PM on September 4, 2010

If the concrete is relatively fresh, it should be easy to grind it down a bit with a cup wheel and an angle grinder.

Put a piece of pipe nipple over the bolt to protect it from the grinder.
posted by Kid Charlemagne at 3:45 PM on September 4, 2010

Cutting the post base at an angle takes 5 minutes and no extra materials. Drilling and grouting will take a day and extra expenses. The only concern would be the post sliding if the slope is very steep, like more than 30 degrees. A couple of nails through the flange will prevent that. You are building a deck, not the Taj Mahal.
posted by JackFlash at 3:48 PM on September 4, 2010

Honestly, if the first thing that occurred to you when you thought about trimming the ends of your posts at an angle was to cut the tops instead of trimming the bottoms, you need somebody else onsite to help you build this thing.
posted by flabdablet at 7:43 PM on September 4, 2010 [1 favorite]

Ok, so it's resolved - in case anyone is interested!
The slope on the tops of the footings was never more than 6 or 7 degress, so I must have exaggurated in a panic.

Nonetheless, I took extra "sonotube" - the cardboard concrete form, cut about a 2-inch piece and fit it around the existing footing. I made sure that the topi of this 2-inch piece was level and then nailed it to the footing. Then I used concrete patching material to "build up" on the existing concrete.
posted by bitteroldman at 6:56 AM on October 12, 2010