Cutting square holes in patio (concrete slab) for 6 X 6 deck posts


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Old 11-06-06, 11:03 AM
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Question Cutting square holes in patio (concrete slab) for 6 X 6 deck posts

I am building a deck off my home that will partially be over a concrete patio. I need to cut holes in the concrete to drill holes for footings. I'm looking for suggestions for the best way to handle this task.

Thank you
 
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Old 11-06-06, 01:20 PM
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Try renting a core drill from the local DIY store. They can put on a 6", 8" or larger bit, and you can drill a round hole in the concrete. A round hole will be less likely to start a crack, especially if you use foam espansion material to separate the existing concrete from any new concrete that you place.
 
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Old 11-13-06, 09:40 AM
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What if I can't find a DIY store that rents core drill, what is another way to get this done..
 
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Old 11-13-06, 10:34 AM
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Cutting square holes in patio (concrete slab) for 6 X 6 deck posts

Try to locate the posts outside of the concrete area to minimize removing concrete. If you move out the outer posts, it still might be cheaper and easier to have a larger deck.

For a 6x6, you will need a hole in the concrete at least 10" in diameter and probably 12" diameter to excavate for the footing that must be at least 4' deep for your frost depth. - Check with the local code office for the actual depth for your area.

There are many local contractors that can knock out the concrete drilling portion in short order. After that, you can excavate for the footings. Probably the best footing would consist of a Sonotube (coated circular form) that you can insert in the excavated hole. Fill around the tube with sand that will fill the voids easily. A little water added to the placed sand periodically will fill the voids completely. The Sonotube can be cut off at the level of the patio to give you clean job. Make sure to embed the appropriate hardware in the concrete.

Depending on your design, your designer may require adequate lateral bracing.

Dick
 

Last edited by Concretemasonry; 11-13-06 at 11:16 AM.
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Old 11-13-06, 10:41 AM
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Wink

Home depot and lowes have a metal saw blade . Has diamond dust on it for your 7 1/4" power saw cost about $40 and last a long time.

ED
 
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Old 11-14-06, 04:07 AM
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The diamond blades for a 7 1/4" circular saw will work to cut about 2 inches deep, but the concrete is probably a minimum of 4 inches thick. The rest would have to be done with a chipping hammer, which may damage the surrounding concrete, and would take a long time.
Any tool rental facility should have a core drill or hand-held concrete saw (rent a diamond blade with it, the fiber blades are slow and don't last long). By tool rental facility I do NOT mean HD, Lowes, etc.
Personally, I would use the hand held concrete saw (quickest and easiest) or the core drill (cleanest cut). Follow that up with a gas powered auger to dig your footer (about 4 feet deep as Dick said.) This is not going to be a simple operation by any means. Before digging, call to have your utilities located so you don't hit a power, gas, phone, cable, or water line!

Pecos
 
 

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