How do I cut through a concrete foundation?
kyrral
| Posted in Construction Techniques on
I have a cabin on sloping land that has about a 5′ crawl space going underneath the house with an existing door into it. I want to cut the foundation beneath the door and add a taller door (and remove dirt to make a walkable space). How could this be done?
Replies
red flags...
In this part of the world [NC AR] that would likely mean you would be cutting the footing in two or nearly so.
That would be a verry bad thing, bisecting your footing.
Even if that is not the case you could end up having a near perpetual pond under your house, depending on the soil type and drainage provisions if any.
it all depends on your site specifics and so on...
Dig it up and inspect what is down there
As was said, there is probably a continuous footer, (at least there probably shoud be).
YOu may have to modify a lot of things to install a door.
Fisrt thing is to dig it out so you know what is there.
And, cutting any amount of concrete is best done with specialized tools, which means hiring a pro.
Berm all the way around inside (add an embankment), dig out and pour embankment in 4 or 6 ft sections at a time.
For somethng as small as you describe, a sledge hammer works fine if you are healthy, finish edges with air impact tool, the $15 HF one will last for your size job.
junk
I'm all for diy and working hard but to have at a concrete foundation to make the door opening lower with a sledge only (and air chisel) is ridiculous.
is ridiculous...
that's
is ridiculous...<G>
that's cuz U is getting too old to swing a sledge with much umph??
Have done 3 like that in the past, faster than calling the pros took -- me about 1 hour for 3 ft wide and 3 foot lower, ya gotta work at the edges vs wahcking at the middle.
Oh, did I forget to say I drill a few holes first with the bulldog? Have not done one with a sledge in the last 4-5 years though, may be harder now?
Have found a 6# sledge works better than an 8# or 10#, just the right combination of momentum and energy. 4# just bounces.
When I was a kid before the fancy machines, watched 2 guys go at an 8" reinforced back wall of a bank building to put in a new vault door. About 2 hours and they had a 4 ft by 7 ft hole with 2 sledges going at the same time.
Watched a 6'-7" 300# Polish guy once split 2 ft dia boulder with 3-4 swings....never could do that.
Ignoring the issue of whether it's a good idea or not, the best approach is to hire a concrete cutting firm.
Short of that, you can get hold of a concrete circ saw or use a beater "skill saw" with a concrete blade to cut a slot an inch or three deep in the concrete. This probably isn't deep enough, though.
You can (with or without the circ saw) drill a series of holes along your desired cut line and chisel it out.
In my grandfather's era you would have gotten a star drill and a 5 pound sledge and drilled holes through it that way.
But note that if this isn't solid concrete but instead CMU (concrete block), and the "cores" aren't filled, I've seen people make doorways in that with a claw hammer and a small cold chisel. Or you can be a little neater (though probably not faster) with the circ saw.
This is not an internet question. You need to ask an engineer.
think the key word in the OP post was CABIN ?? aint the leaning tower he the foundation is messing with
My fault. The last time we rented a "cabin" this was it.
http://gfretwell.com/ftp/georgia/cabin%20rear.jpg
If you mean this I understand
http://gfretwell.com/ftp/New%20Mexico%20Arizona%202006/cabin.jpg
I have done similar jobs using a large hammer drill to drill a series of closely spaced 5/8" holes across each side of the opening, and then finishing with a sledge hammer. (I agree with junkhound that a 6# hammer is best for this).
The $300 I paid for the Bosch hammer drill was about the same as what a concrete-cutting company would have charged for the job, but I still have the hammer drill, which I have used for a lot of other projects.
If you dig out under the section to be removed, gravity will help a lot.
You can dress the rough surfaces of the remaining sides using an air chisel if you have a good compressor, or you can use a diamond blade in an angle-head grinder (extremely dusty, though), or a mash hammer and chisel.
One advantage of hiring it done is that the cuts will be glassy smooth and precise.
What I've decided to do from the comments
Thanks all. I got some good feedback. What I am going to try is to run a diamond blade on a circular saw both inside and outside (2 1/2" each cut) and then jackhammer the remainder. I am also going to frame the door in 4x4's on top of another footing. That should cure safety issues.
That won't cure it
The problem is the concrete. Putting a wood 4x4 doesn't cure that. Things that may help are not damaging the rebar, pinning new rebar with Simpson et22 (or similar) epoxy, and painting old concrete with a bonding agent. This really isn't something you should do lightly.
from iPhone pls excuse any mistakes
That won't cure it
The problem is the concrete. Putting a wood 4x4 doesn't cure that. Things that may help are not damaging the rebar, pinning new rebar with Simpson et22 (or similar) epoxy, and painting old concrete with a bonding agent. This really isn't something you should do lightly.
from iPhone pls excuse any mistakes
Concrete chainsaw
If you wear yourself out with the jackhammer before you are done, there are two other tools that can do this job, that one man can handle.
The first is a concrete chainsaw, light and easy to handle, but it is pricey.
The second is a 14" dimond blade on a Makita portable gas-powered cutoff saw with a water cooling attachment.
That one can be rented at most places that rent tools. I own one myself and it cuts through concrete, stone and asphalt. Wear heavy rubber gloves, safety glasses, ear plugs, and a face shield, along with a rain jacket. It will be the loudest and messiest job you will probably ever do.
Good luck.
Concrete Saw
The way to go is a concrete ring saw. It can plunge cut up to 10" which allows you to cut from the outside only. The regular 14" concrete saws only allow you go go about 4" - 5" before hitting the arbor. Then you have to line it up just right cutting from the inside.
What I've seen the professional concrete cutters use most recently is the hydraulic chain saw. This was cuttting through foundations about 10" thick, though I'd imagine thicker is easily possible with a longer bar. Mirror-smooth cut.