Post hole depth

Nik · May 21, 2005

How deep do postholes need to be for a 4" by 4" wood post. This is for a garden fence. The posts are 8' long and will use 5' galvanized fence to keep my dog and other critters out of the garden. Is 2' good enough? The soil is clay with lots of rocks. May need to consider a posthole digger but I may manually dig them as I only need about 9 posts.

seapea · May 21, 2005

Another question is how wide. I think 9" is typical, but I'm not sure.

RobA · May 21, 2005

I live in southeast PA too. The frost line is lower than 2 feet. I think you risk having the posts lifted in the winter if you only go that deep. I put in 4x4's for a garden fence and could only get down about 1-1/2 to 2 feet in some areas. For those I screwed in some 4 or 5 inch galvanized lag screws 2 or 3 inches from the bottom of the post to help it from being lifted.

Lloyd_E · May 21, 2005

Nik,

I am digging by hand and placing 4x4x8' posts down 30-34". I am packing soil and leveling as I fill.
Will be 3 rail plus cap at 5' high for horses when finished.

I did a wide vertical board fence and used 6x6x10' hemlock and sunk them 36+". The wind still moves the fence on occassion.

Hope this helps.

Lloyd

PS: will be renting auger for remaining 200+ posts

tjkadar · May 21, 2005

We generally try to get an 8' post 3 feet into the ground. It isn't too bad until you hit clay, then it can be slow going. A good set of posthole diggers makes doing it by hand feasible. Nine holes isn't too bad.

Nik · May 21, 2005

Thanks for the advice. I will try to dig deeper than 2 feet with my manual post hole digger. I will be using 1 inch by 2'inch galvanized wire fencing for the garden. Would love to use a post hole digger on my BX23 however I would probably not need it after this project. (Cost for the WOODS PHD 25 with 9 inch auger is about $900.00).

NoTrespassing · May 22, 2005

Nik,

Are you using the "clamshell" stlyle or "auger" style post hole diggers? When I used to dig holes manually /forums/images/graemlins/wink.gif (I've got both a 2-man motorized auger and a 3 point for the Kubota now) I would use the auger http://www.epinions.com/hmgd-Lawn_and_Garden-Hand_Tools-All-Ames_170_Iwan-Pattern_Auger to start the hole and the clamshell to pick out any rocks or tree roots and maybe to clean out the very bottom of the hole.

I brought the manual auger to a friends house yesterday for 2 holes he needed to dig and neither he nor my other friend that was there had ever seen one. They were amazed at what a nice hole it made. Then they started razzin me about how old I was and that the auger must be an antique from an auction. Truth is, the auger is only 5 yrs. old.

I know what people are thinkin, why didn't I take the 2-man motorized one. Truth is I had already loaned the 2-man out for the weekend.

MarkStewart · May 22, 2005

I just put in about 12 4x4 posts for a small garden in rocky clay soil. I used a combination of 1man gas powered auger, manual post hole digger, and large steel digging bar.

Anytime I ran into rocks etc. I used digging bar to continue. It's alot of work but the other tools seem to stop digging when they hit anything really hard etc. I was able to dig about 3' holes.

I think the frost line around here is around 4' though. But for what I'm doing I don't think it will matter much
anyway.

gabby · May 22, 2005

</font><font color="blue" class="small">( For those I screwed in some 4 or 5 inch galvanized lag screws 2 or 3 inches from the bottom of the post to help it from being lifted. )</font>

You can also buy some 6 inch galvanized landscape spikes and drive them through the 4x4 post so that the head and the point both protrude an inch and a half or so from opposite sides. Nail them in pairs perpendicular to each other crosswise. I do this for 4x4 building posts set in concrete to provide load bearing as well as uplift resistance.
gabby