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gogden51
Best driveway prep

What is good, better, and best in prepping for a driveway pour? I'm seeing different approaches in my neighborhood and would like to get a good job for my own driveway. Fact or Myth: should rebar be tied to an adjoining basement wall? I live in an area where the freeze-thaw cycle occurs. Not as much snow as Boston, but cold enough. Thank you.

dj1
Re: Best driveway prep

"What is good, better, and best in prepping for a driveway pour?"

So much has been written on this subject, no need to repeat, search on line. What you do depends much on your area, your code.

"Fact or Myth: should rebar be tied to an adjoining basement wall? "

Again, you have to look up your code. In my area only a living space addition must be tied to the existing slab. A driveway, even when touching the house slab, is an independent slab.

Mastercarpentry
Re: Best driveway prep

Best to not tie them together. The weight/bearing ratios between a house and a driveway slab are very different so there will be differential movement. Unless both sides are designed to make that connection attempting to stop that will break one part or the other. Tying an addition in does not have this differential involved so it works well there.

The most important part of a driveway slab is the ground prep, soil compaction or bearing ability in particular. Simply digging out a certain amount and adding gravel (compacted or not) will not compensate for soil compaction or movement. Best to do the initial excavation, assess the seen soil types hoping for consistency, the compacting with fill as required to obtain the correct elevation for the gravel substrate which gets a vibratory tamping itself. Now you can form, pour, and finish.

Where movement is expected (freeze-thaw areas and differing soil types) I prefer to see actual expansion joints or at least cut joints of 1/4 slab thickness or a little more. No "Zip Strips" as these are too shallow. I like those joints 8' to 10' apart instead of the usual 12'; this allows for more movement with less risk of cracking. Rebar should be continuous and 6"X6" wire mesh should also be used. The concrete should also be air-entrained to help prevent freeze-spalling. I'd also consider a 5" to 6" thickness if the soil is not stable instead of the usual 3 1/2" to 4" you usually see. After the pour sets, use a sealer to keep surface moisture out and you'll have a trouble-free driveway that lasts.

Phil

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