I need to cut a section out of my foundation directly below a window to install a bigger window.

My question is what should I use to cut the concrete out. Should I just go buy a dry blade for my circular saw and go for it? Rent something from HD or something else?

 

Is it a poured concrete foundation? Block? Something else? How thick and how long will the cuts be?

 

We have no picture, no info on how much larger it needs to be.
In most cases I'd be using my cheap ciruler 7-1/4, saw with a diamond blade to make the main cuts.
I use my cheap saw because concrete dust is the kiss of death to any saw, a diamond blade will out last a cheap abrasive blade 10 to one.

 

The job would go quickest using a rental Target saw, equipped with a masonry blade. A typical 14" blade will cut close to 6" deep, getting there in 2 or 3 passes. If the wall is thicker, you can cut from both sides.

A cheaper way would be to buy a few masonry blades for your circular saw. I've been using an old Craftsman 7-1/4" saw for more than 35 years, dedicated for concrete cutting only, and it still shows no signs of giving up the ghost. You have to make much slower, shallower cuts than when using a Target saw, and it heats up to the point of not being able to hold it by the handle without wearing decent gloves, to keep from getting burned.

 

The guys that cut the opening for my 32 x 80 door used a chainsaw with a diamond blade and a water spray attachment. They were done before I would have been able to find the wrench to put a diamond blade on my circ saw. Cut through 12 inch block in one pass like butter. IIRC, they charged $200. I'm sure it's outrageously expensive, but sure was the right tool for that job.

 

Thanks for the advice everyone. Its a poured concrete foundation. I haven't measured but it looks like a standard thickness for a house maybe 8-10 inches thick. The cut will be about 6 inches vertical either side and 2 feet wide.

I'm thinking I'll just go buy a diamond blade and use my curricular saw. If it takes a little while to get through that's okay.

I've seen utube videos of the chainsaw cutter. Pretty cool.

My hesitation on renting something is they make you buy a new blade which isn't cheap for the bigger machines and useless to you once you return the machine.

 

Probably a stupid question but.....

All the blades I'm seeing are 7 inch and not 7 1/4 like a standard circular saw. Other than the slightly smaller blade/cut depth will they fit my craftsman circ saw?

Thanks!

 

Just because a saw is 7¼" doesn't mean you can't use smaller blades. Note also some circular saws are 7" so the blade is just made to fit both sizes.

 

You may want to call another rental place or two. The place I rent from measures the blade with micrometer when you take and return it. If the wear is more than x amount they charge you an additional fee, but for my small jobs I've never been charged the blade wear fee.

 

In the half-dozen or so times I've rented a Target saw in the last 45+ years, I've never been charged a blade wear fee. Nor have I ever observed any blade measuring by anyone, just a casual glance and that was it. Granted, all of my usage has been for short cuts (all but just one or two easily less than 25' each), so that might have been the reason for no blade-wear charges.

Then too, it might just be my honest-looking face.

 

Much easier to rent from www.homedepot.com in my opinion.