Folks with experience with concrete

[Muse]

This is my first use of concrete. I am doing a tricky repair on my garage. One front corner next to the manually raised door was badly designed. Water runs right onto that corner (both from garden rain runoff and the downspout from the roof) and they somehow dropped the ball on having a raised section of foundation there (IOW, there is no raised concrete right at the corner and they had ordinary wood going straight down to the concrete base... naturally it became rotten and termite infested). The adjacent side wall has a section of concrete raised foundation about 4.75" high running up to the front wall and 2x6 pressure treated wood on top. I've removed about 2 feet of the bottom of the structure at the problem spot and am planning tomorrow to pour concrete to hopefully that 4.75" height to form the missing piece of foundation. I will let that set a day or so and on top of that attach pressure treated 2x6 and attach short pressure treated extensions vertically to the structure above, sort of like prosthetic legs on an amputee! To secure those extensions I'm going to run two lag bolts through steel L brackets that are already there at the bottom and think I will attach steel plates as sort of bandaids between the OK upper vertical supports and the newly added pressure treated prosthetics on the bottom.

To facilitate creating the missing 4.75" high concrete foundation right at the corner, I am designing a form for the concrete pour out of pieces of plywood that I will screw together. I am making the form 1/2" higher than the pour and hope to shake and/or tamp down the just-poured concrete to a hopefully level surface.

I figure to line the inside of the forms with waxed paper as a releasing agent.

Before mixing the concrete: I plan to wash the existing concrete before applying the form and concrete and then, after letting it dry, apply Quikrete Concrete Bonding Adhesive, probably with a brush, maybe a small roller (this video inspires confidence).

I bought two 80 lb bags of Sakrete 4000 lb High Strength Concrete Mix for this job, figuring I need about 0.7 cubic feet. One bag is only good for 0.6 cubic feet.

Once the concrete is set a day or so I plan to fasten the pressure treated 2x6 on top of it using two 2.75" 3/16" tapcons with holes predrilled by a hammer drill with 5/32" carbide drill bit.

I'm looking for any tips on getting this plateau of concrete as close to 4.75" off the existing concrete as possible, and level. Can I maybe make some kind of adjustments after removing the form? Getting the top level and smooth won't be easy with the form in the way but I figure I should have the form extend higher than the pour, thus the extra 1/2" in its height.

 

[drnickriviera]

Pics? Why cant you just make the form at the finished height of the concrete?

 

[Greenman]

Form to the height you want. There should be a mechanical connection to the existing concrete.

 

[Muse]

Pics? Why cant you just make the form at the finished height of the concrete?

I figured it would extend above and pour over? Maybe you're right though. I can just pour in less to start and build up, putting a little more in at a time, level, a bit more, level, etc. until I get to the top. Then, leveling well will be easier... I will have to adjust my form pieces to do that. I can do that this morning.

 

[Muse]

Form to the height you want. There should be a mechanical connection to the existing concrete.

There is some. There are 4 rusty nails sticking up out of the concrete at one point. It's kind of knarly. Some will actually go on top of dirt. I should maybe dig out some more of that dirt to assure a concrete depth of at least 2". The two bags of concrete I have means there will be plenty to enable that.

This Quikrete Concrete Bonding Adhesive video is pretty reassuring that there won't be a problem with bonding the new pour with the concrete under it.

 

[Greenman]

I figured it would extend above and pour over? Maybe you're right though. I can just pour in less to start and build up, putting a little more in at a time, level, a bit more, level, etc. until I get to the top. Then, leveling well will be easier...

You're overthinking this. Dump the concrete in, stab it with a stick a hundred times to be sure there no voids. Use the same stick to screed the top, use a sawing motion. That's it, you're done.

 

[Muse]

Pics?

I took some pics. I think this one is pretty good (can you see it?):

You can see in the pic that screeding will be trickier because of the two L brackets extending out the top of the pour. No biggie, I guess.

On the right is an area I plan to pour level with the surounding concrete. To the left of that is where I will build my 4.75" high concrete dam, It will extend up to the second of the 3 holes you see on the L bracket. The top 2 holes (one on each of the 2 L brackets) are ones I drilled. I will run galvanized lag bolts through those two holes into the PT 4x4s that will attach to the 4x4s coming down from above.

Looking at the concrete in the pic you can see that they did some weird stuff there. They had something going on that was removed, obviously, maybe two things from two different modifications to the structure. Boy, the garage was a mess when I bought the place. It's been 17 years, but I'm planning by next week or so to have the basic repairs done. By next year to do some other things, interior painting, some shelves. I want it to be able to withstand rain storms by a week or two right now.

You're overthinking this. Dump the concrete in, stab it with a stick a hundred times to be sure there no voids. Use the same stick to screed the top, use a sawing motion. That's it, you're done.

Yeah, I tend to overthink a job when I have never done it before. Building my first PC, for instance. I was super careful. I'm much more cavalier about it now, but I still like to do my homework.

I saw a video where a guy showed a neat trick. He used a reciprocating saw with the blade removed, just shoved the shoe up against the form and ran the saw to vibrate the whole mass. It worked the concrete down level in 5 seconds or so.

 

[Greenman]

A random orbit sander works as well.

You should actually tie that corner together with some rebar. Dowel it into the existing stem wall, and the footing where those L brackets are. The post you cut off really should be continuous up to the top plate (though a a full length scab on one side will help a lot) . I know that might present some difficulty to a fellow that doesn't own every tool made, but it is doable, and worth the effort.

 

[Humpy]

I would get rid of those brackets too, they'll probably do more harm than good.

 

[Muse]

A random orbit sander works as well.

You should actually tie that corner together with some rebar. Dowel it into the existing stem wall, and the footing where those L brackets are. The post you cut off really should be continuous up to the top plate (though a a full length scab on one side will help a lot) . I know that might present some difficulty to a fellow that doesn't own every tool made, but it is doable, and worth the effort.

Well, I actually did something like this yesterday, on recommendation from guy at Berkeley Tool Lending Library, where I borrowed a mortar tub, hammer drill and 3 carbide drill bits. I just took a picture of it (can you see it?). As seen in photo, I drilled four 1/2" holes into the slab and drove in ~5" lengths of 1/2" rebar, then wired on a couple of pieces of 1/2" rebar horizontally. Also, drilled some 5/32" holes and inserted tapcons to give the pour something extra to grab onto. You can see (if you look close), there are 4 rusty nails sticking up from that square piece of cement at odd angles. I'll leave them there, figure they will give extra grab along with the tapcons I drove in yesterday. I have no idea what that cement square is doing there. It seems to be outside the garage structure/foundation. The house itself was built in 1910, the garage later (I think), but even the garage seems to have been modified, maybe multiple times.

I'm debating about using or removing those L bracket pieces. They have strength, although pretty rusted. Running galvanized lag bolts through the holes I drilled, one in each at the top, and into the left pressure treated 4x4 segment I'm going to install after the pour and application of the 2x6 sill plate will give some extra firmness. However, I think I need to apply plates to join the upper 4x4s that come down from the roof. Screw those plates to those upper 4x4s and the pressure treated prosthetics I'm going to install. Leaving the L brackets will mean I have to cut a knotch in the 2x6 sill plate to fit over one of them, but that isn't a big issue. Can use a drill to do that, basically.

I washed the cement yesterday. It's fairly clean now. Don't know how clean it needs to be. I have a quart of Quikrete Concrete Bonding Adhesive that I'll apply before the pour.

The 2x6 PT I'm going to place on top of the dam is going to butt against the one that is already there that you can see on the side wall, to form an L. l That's going to be a very wet area when it rains but I figure the dam will keep the wood above shielded from the puddles/runoff.

You can see in the picture where I marked with a sharpie the outside dimensions of the 4.75" high, flat plateaued concrete dam envisioned. Have to finish the forms today, whatever else I do. Don't know if I'll get to pour today, if not, tomorrow.

 

[Humpy]

The bracket that points into the garage will leave a thin section of concrete near the edge that will probably crack and spall off before too long. The other one, though not as bad, just creates a place for cracks to propagate from while only providing an anchor point that can be easily replicated with a tapcon.

Drill a hole into the side of the old curb and use rebar to pin the old to the new like greenman said.

 

[Muse]

The bracket that points into the garage will leave a thin section of concrete near the edge that will probably crack and spall off before too long. The other one, though not as bad, just creates a place for cracks to propagate from while only providing an anchor point that can be easily replicated with a tapcon.

Drill a hole into the side of the old curb and use rebar to pin the old to the new like greenman said.

Just did that. I don't think there's enough room to go in from the side, but it looks to me like going in from the end works fine. You can see the sharpie marking I made to show approximately where the dam's borders are. I think it may extend a bit over those, that was approximate.

See what I just did with the rebar addition:

Alright, I think I will do away with those brackets. Thanks!

 

[Muse]

A random orbit sander works as well.

You should actually tie that corner together with some rebar. Dowel it into the existing stem wall, and the footing where those L brackets are. The post you cut off really should be continuous up to the top plate (though a a full length scab on one side will help a lot) . I know that might present some difficulty to a fellow that doesn't own every tool made, but it is doable, and worth the effort.

Trying to figure this out. Full length, you mean a wooden member extending from the top plate all the way to the floor? I was thinking a steel plate, maybe a foot long or something and screws, nails...

 

[Muse]

The bracket that points into the garage will leave a thin section of concrete near the edge that will probably crack and spall off before too long.

The other one, though not as bad, just creates a place for cracks to propagate from while only providing an anchor point that can be easily replicated with a tapcon.

I see what you mean about the bracket pointing into the garage, that the concrete on the inside of it is apt to crack and fall away at some point. I don't understand the bolded statement. Where would that tapcon go?

 

[Humpy]

I see what you mean about the bracket pointing into the garage, that the concrete on the inside of it is apt to crack and fall away at some point. I don't understand the bolded statement. Where would that tapcon go?

Tapcon(s) to fasten a new steel bracket or strap to the concrete to take the place of what you intended the old bracket to do.

 

[Muse]

Tapcon(s) to fasten a new steel bracket or strap to the concrete to take the place of what you intended the old bracket to do.

I don't understand. You're suggesting I cut off both steel brackets, right? Are you suggesting I install a "new steel bracket?" Where?

 

[Humpy]

I don't understand. You're suggesting I cut off both steel brackets, right? Are you suggesting I install a "new steel bracket?" Where?

I'm not 100% sure what the intent of saving the old bracket is/was.

I assumed it was to have something to attach the post to. You could fasten a new bracket to the new concrete, or through the new bottom plate into the concrete, something like this:

Typically there would be an anchor bolt embedded in the concrete to bolt a hold down to that would then be attached to the new post sort of like this:

With such a small chunk of concrete sitting on a slab of unknown thickness a bolt seems kind of pointless though. Sorry if I just made it more confusing, it looks like you have it figured out pretty well, you just have to improvise these repairs the best you can unless you want to go all in.

 

[Greenman]

Just did that. I don't think there's enough room to go in from the side, but it looks to me like going in from the end works fine. You can see the sharpie marking I made to show approximately where the dam's borders are. I think it may extend a bit over those, that was approximate.

See what I just did with the rebar addition:

Alright, I think I will do away with those brackets. Thanks!

Looks great! I knew you could do it. The scab on the post I was talking about is indeed a 2x4 that goes from the top plate to the bottom plate.
Dumping the L brackets is a good idea as well. I hadn't thought about the concrete spalling out behind them. Good catch from Humpy.

 

[Greenman]

I'm not 100% sure what the intent of saving the old bracket is/was.

I assumed it was to have something to attach the post to. You could fasten a new bracket to the new concrete, or through the new bottom plate into the concrete, something like this:

Typically there would be an anchor bolt embedded in the concrete to bolt a hold down to that would then be attached to the new post sort of like this:

With such a small chunk of concrete sitting on a slab of unknown thickness a bolt seems kind of pointless though. Sorry if I just made it more confusing, it looks like you have it figured out pretty well, you just have to improvise these repairs the best you can unless you want to go all in.

My guess would be a 12" footing without any rebar in it at all. Very common on those old houses. The L brackets were probably installed at a later date after someone hit the edge of the opening with a car. They didn't do portal walls back in the day.
For a DIY guy, he's done a darn fine job. I'd have had a different approach, but I'd have shown up with $6000 worth of gear, $300 worth of material, and a bill for $1100 when I finished. He's way ahead of the game at this point.

 

[Muse]

The post you cut off really should be continuous up to the top plate (though a a full length scab on one side will help a lot) . I know that might present some difficulty to a fellow that doesn't own every tool made, but it is doable, and worth the effort.

TBH, a reason I gave up on the idea of replacing the 4x4s on that right side of the front of the garage is that I figured to do that I'd have to remove the contraption that allows me to raise and lower the door. Until I got the OSB on the side wall (still haven't put up the Hardie planking because I want to complete repair of the corner first, I decided) ... until I got that OSB up, everything in the garage was unsecured. Every day I worked on the wall before the sheathing was up I'd bring my tools out in several 5 gallon buckets and have to bring all that stuff back in the house if I didn't want to chance leaving it out there. Chances are nothing would happen to it but just the thought of my tools being swiped was enough to make me get paranoid about it.

So, the idea of removing the whole 4x4s, I figured would require removing the door hinge on that side, meaning I would no longer be able to shut the door and lock it until I got it all put together. Right now, the right side of the door opening/closing contraption is intact except for the spring, so it takes some muscle to open and close the door, but I can do it! The door won't stay up on its own, so I shove a ~7' 2x4 under it to hold it up while I'm working in there. This arrangement lets me leave all my tools and materials in the garage...What a relief! Over the years I've lost a few things I left in the yard to theft. Nothing huge, but I make a habit now of never leaving anything out there that I would be much upset at losing.

 

[Muse]

Instead of tapcons to hold the 2x6 PT sill plate to the top of the concrete I'm pouring I decided to insert galvanized threaded rod directly into the slab before I pour. I bought today a 2 foot long 1/2" "plated" threaded rod. The plating, I figure, has to be zinc. It looks it to me. I figure to cut two ~9" pieces from the rod and insert them into holes I will drill in the slab (before I put on the form and do the pour). The guy at the tool lending library thinks I should epoxy them into the slab and suggests using a 9/16" drill bit rather than 1/2" so I can get more epoxy in the holes to better secure the rods.

I'm hoping I can get the rods close to vertical so the pre-drilled sill plate will fit over them easily ... i.e. without having to widen the holes in the plate (which is a good reason to drill bigger holes, actually). I figured galvanized rod was the thing to do because of contact with the PT sill. I have SS washers to fit over the rods onto the sill, but only ordinary 1/2" nuts, but figure the nuts won't touch the sill and they'll suffice. This arrangement is obviously stronger than a couple of 3/16" 2.75" tapcons through the sill into the hardening pour.

 

[drnickriviera]

or do you think mudsill anchors would be easier to use? Not sure how much room you have in there

 

[Micrornd]

Instead of tapcons to hold the 2x6 PT sill plate to the top of the concrete I'm pouring I decided to insert galvanized threaded rod directly into the slab before I pour. I bought today a 2 foot long 1/2" "plated" threaded rod. The plating, I figure, has to be zinc. It looks it to me. I figure to cut two ~9" pieces from the rod and insert them into holes I will drill in the slab (before I put on the form and do the pour). The guy at the tool lending library thinks I should epoxy them into the slab and suggests using a 9/16" drill bit rather than 1/2" so I can get more epoxy in the holes to better secure the rods.

I'm hoping I can get the rods close to vertical so the pre-drilled sill plate will fit over them easily ... i.e. without having to widen the holes in the plate (which is a good reason to drill bigger holes, actually). I figured galvanized rod was the thing to do because of contact with the PT sill. I have SS washers to fit over the rods onto the sill, but only ordinary 1/2" nuts, but figure the nuts won't touch the sill and they'll suffice. This arrangement is obviously stronger than a couple of 3/16" 2.75" tapcons through the sill into the hardening pour.

If it said "plated", it's probably cadmium plated, not zinc.
Zinc would say "galvanized" if electroplated or "Hot Dipped" if (obviously) hot dipped in zinc.
Zinc plated or dipped is dull, Cad plated is shiny

 

[Muse]

If it said "plated", it's probably cadmium plated, not zinc.
Zinc would say "galvanized" if electroplated or "Hot Dipped" if (obviously) hot dipped in zinc.
Zinc plated or dipped is dull, Cad plated is shiny

It doesn't really look shiny. To me it looks like maybe a little more thorough zinc electroplating effect than you typically see on zinc electroplated fasteners. I just called the company (The Hillman Group, out of Cincinatti), and am told that it's zinc plated. Also, that it's mild carbon steel, cold rolled. Googling, I read something suggesting that cadmium plating is probably not that common now except for applications that require it at least partly due to the toxicity of cadmium.

Yes, I think they should have labeled it galvanized, which is, I think, what you usually see on zinc electroplated hardware.

or do you think mudsill anchors would be easier to use? Not sure how much room you have in there

Hmm. I like that, will see if I can find something that will fit in the narrow space. The 2x6 mudsill will be 14.5" long. 1/2" overhangs the outside of the outside 4x4, so doesn't count. Between the two 4x4s that will rest on the mudsill is 7" and the 2 threaded rods with washers and nuts holding it down are in that space. Now, do you have the idea that mudsill anchors would be instead of the threaded rods? Or in addition? I figured the latter, that they would be better than the alternative, which I figure is toe nailing with hot dip galvanized nails.

 

[Muse]

I just cut off both L straps, what a job! Didn't want to remove and replace the rebar. I managed to cut off the straps regardless. The bases remain, though. The threaded rods will be pretty close together, but that's the way it goes. Maybe not much more than 4" between them, 'cause the hammer drill needs to be vertical to drill the holes and the posts on the sides get in the way.

Question: To the south (as you enter the garage, you're going north) you can see the area where there's the square with tapcons driven into it and dirt next to that. That area I intend to fill with concrete (level with the slab) at the same time I do the 4.75" high pour into the form I'm making. The dirt is dry right now and I think I have to get it wet or it will suck the water right out of the concrete. So, I'm wondering if I should (in addition to getting that ground wet, or at least damp) place down a moisture barrier, maybe a layer or two of waxed paper.