miamicuse
Civil/Environmental
- Nov 12, 2011
- 22
thread194-495078
This is a continuation of a previous thread (now closed) on solution to replace a wood fence post 4X4 or 6X6 at the same location. I have resolved the issue, somewhat but like to get some feedback, in addition, I like to reply to some of the previous suggestions.
The issue at hand is when you have to replace a wood post due to damage or rot, and said post was previous set in concrete, which is required by code where I am), how do you avoid the post hole getting bigger and bigger with each "iteration"?
With a regular fence post most just cut off the bad post, and dig a new hole say a foot over, and shift all the posts along the fence line, this avoids having to dig up the old concrete, and the digging of the new hole in regular soil is much easier, but in the case of a gate post, it has to be in the same exact spots, and if you are replacing the posts say every 10 years (due to termites, moisture penetration etc...) each time the crater gets bigger and bigger, from 8" to 12" to 16" to 22" etc...I have one 6X6 posts I pulled out and the hole from the concrete anchor and the digging around it is in excess of 24" in diameter.
Obviously, the easiest solution is to just put in as much concrete is needed to fill the bigger hole. In this case cost is not a concern, I just want to get back to a normal sized hole that's workable.
One thing I did try, and that is to backfill the entire hole with the same dirt, compact as much as possible, then dig a new hole into the backfilled soil, that doesn't work. The newly compacted soil does not stay firm enough. I did an experiment. Dug a 14" post hole 24" deep. Then backfilled that hole with the excavated dirt, compact by hand and also add water to help compaction. Waited one week of time, then in the backfilled area dug a smaller 8" hole 24" deep. I also dug a new 8" hole 24" deep only 2 feet away, at a location that has never been backfilled. Once dug, I jumped up and down near both holes. The result is the soil in the backfilled hole collapsed and caved, where the other hole has no such issue.
Out of all the solutions proposed, there was a suggestion to brace in sonotube into the large hole, fill it with concrete and post, then when set, backfill the soil around the sonotube and compact. That may have worked but I never tried it, I may one day.
The other suggestion was instead of digging out the post and concrete anchor, hire a core drilling company that can drill say an 8" hole 24" deep, to just drill a fresh hole in the concrete, keeping most of the old concrete in the ground. This also may work. In fact I may try this very soon with a set of six wrought iron fence posts I have at another location.
What I end up doing in this particular case, was I spoke to a local old time mason about this issue, and he suggested a method. What he suggested was after I dug out the old concrete, and have this big crater 24" or so deep, 24" in diameter, instead of backfilling with regular soil, or fill the entire crater with concrete, I could use Portland cement. So basically I bought an 80 pound bag of Type II Portland cement, and used the entire bag to mix with a wheel barrow full of regular soil/sand. Once mixed, I backfilled the hole, compact and wet it with water. Left it alone for e few days. then excavate a new hole. I did that and did the same jumping up and down near the hole and there was no collapsing of the soil. The new backfill feels a bit stiff but still can be excavated with a regular shovel or post hole digger fairly easily. That's what I end up doing and set the posts, so far it has been fine, no leaning, no setting with the two 5' gates.
My question is, by mixing the Portland cement and soil (no other additive, no aggregates, no line), what has happened to the soil? It seems to be more stable but is it really?
This is a continuation of a previous thread (now closed) on solution to replace a wood fence post 4X4 or 6X6 at the same location. I have resolved the issue, somewhat but like to get some feedback, in addition, I like to reply to some of the previous suggestions.
The issue at hand is when you have to replace a wood post due to damage or rot, and said post was previous set in concrete, which is required by code where I am), how do you avoid the post hole getting bigger and bigger with each "iteration"?
With a regular fence post most just cut off the bad post, and dig a new hole say a foot over, and shift all the posts along the fence line, this avoids having to dig up the old concrete, and the digging of the new hole in regular soil is much easier, but in the case of a gate post, it has to be in the same exact spots, and if you are replacing the posts say every 10 years (due to termites, moisture penetration etc...) each time the crater gets bigger and bigger, from 8" to 12" to 16" to 22" etc...I have one 6X6 posts I pulled out and the hole from the concrete anchor and the digging around it is in excess of 24" in diameter.
Obviously, the easiest solution is to just put in as much concrete is needed to fill the bigger hole. In this case cost is not a concern, I just want to get back to a normal sized hole that's workable.
One thing I did try, and that is to backfill the entire hole with the same dirt, compact as much as possible, then dig a new hole into the backfilled soil, that doesn't work. The newly compacted soil does not stay firm enough. I did an experiment. Dug a 14" post hole 24" deep. Then backfilled that hole with the excavated dirt, compact by hand and also add water to help compaction. Waited one week of time, then in the backfilled area dug a smaller 8" hole 24" deep. I also dug a new 8" hole 24" deep only 2 feet away, at a location that has never been backfilled. Once dug, I jumped up and down near both holes. The result is the soil in the backfilled hole collapsed and caved, where the other hole has no such issue.
Out of all the solutions proposed, there was a suggestion to brace in sonotube into the large hole, fill it with concrete and post, then when set, backfill the soil around the sonotube and compact. That may have worked but I never tried it, I may one day.
The other suggestion was instead of digging out the post and concrete anchor, hire a core drilling company that can drill say an 8" hole 24" deep, to just drill a fresh hole in the concrete, keeping most of the old concrete in the ground. This also may work. In fact I may try this very soon with a set of six wrought iron fence posts I have at another location.
What I end up doing in this particular case, was I spoke to a local old time mason about this issue, and he suggested a method. What he suggested was after I dug out the old concrete, and have this big crater 24" or so deep, 24" in diameter, instead of backfilling with regular soil, or fill the entire crater with concrete, I could use Portland cement. So basically I bought an 80 pound bag of Type II Portland cement, and used the entire bag to mix with a wheel barrow full of regular soil/sand. Once mixed, I backfilled the hole, compact and wet it with water. Left it alone for e few days. then excavate a new hole. I did that and did the same jumping up and down near the hole and there was no collapsing of the soil. The new backfill feels a bit stiff but still can be excavated with a regular shovel or post hole digger fairly easily. That's what I end up doing and set the posts, so far it has been fine, no leaning, no setting with the two 5' gates.
My question is, by mixing the Portland cement and soil (no other additive, no aggregates, no line), what has happened to the soil? It seems to be more stable but is it really?
