Post hole auger size

[Anonymous-0]

What size auger bit for 4x4 deck posts ?

 

[Nitro]

How much concrete do you want to use ? 4x4 post ? 4 to 6 inch auger

 

[Mike (WA)]

6 inch minimum (4 inch hole will be smaller than the post)- 9 inch better, gives a little leeway for placement, and enough capacity for concrete to actually anchor the post.

 

[Mike (WA)]

6 inch minimum (4 inch hole will be smaller than the post)- 9 inch better, gives a little leeway for placement, and enough capacity for concrete to actually anchor the post.

 

[Sean Feeney]

Right Triangle Diagonal will be 5 5/8" across need a 6" auger.

 

[Anonymous-0]

9" is better cause you can pour concrete in the hole for a footing that won't slooowly sink under the weight of the deck. Mine is on hand dug 6X6's and every couple years I gotta put shims under it to bring it back to level. Currently at 2 1/2".

 

[bc]

Your 4x4 posts are really 3 1/2 by 3 1/2 which is about 5" at the diagonal. 6" auger will work. Ideally you want a bell shape at the bottom which requires a little/lot of hand digging to do it and nearly impossible to do. And me, I put a little gravel in the bottom, paint a coat of asphalt foundation coating on the sides and bottom of the post in the ground and backfill with sand. Concrete helps hold moisture so the wood rots quicker and also creates a larger area for the freeze/thaw process to begin pushing it out of the ground and knocking your deck off level in 10 years.

Depends upon how much weight they support? Maybe you need a 12" hole to have a good solid footing.

I personally wouldn't put a deck post in the ground any more cause of movement and termite and rot issues. I'm old enough to have to had replace some as well as fence posts. I'd dig a hole to the frost level, (3' here) put a piece or 2 of rebar in, get some round cement cardboard forms from home cheapo or lowest and cut off short sections that will stick up above the ground for a neat appearance. Level all the tops. Then you can use those metal post brackets in/on the concrete or use the concrete bases to set your post on.

 

[JML755]

(quoted from post at 14:04:01 03/09/09) What size auger bit for 4x4 deck posts ?

I agree with BC. Use a 6" auger and pour a pier down to below the frost line. Also, be aware that if you are putting a deck next to a newly built house, any piers/posts near the house are likely setting on/in backfilled earth. Depending on how it was backfilled, you will get more or less settling, but there will probably be some. My house was built over 20 years ago and the piers close to the house have settled about 1.5" over the years while the others further out settled about .5".

 

[bc]

To further discuss what JML said, I don't attach decks to the side of the house anymore. Too many issues with the water getting in under the siding and into the sill even with a rain cap.

Free standing decks on piers about a half inch or so from the house. If there is any settling, you can go under it with a jack and shims and level it.

A 2 story deck is another issue though.

 

[RayP(MI)]

When I built my polebarn, they sold me 12" (1foot) on diameter concrete cookies to put down in bottom of hole to support the posts. This of course meant a 12" (1 foot) diameter hole. The cookies will not hold water around base of post like the poured concrete boots will. Backfill with sand and light gravel. would suggest same for your decking posts. Make sure that the ground has settled thoroughly before starting this project.

 

[Spook]

I always use a 12 in auger. That way I have a little wiggle room to adjust the post position.