|
| Author |
Message |
vman14
Member
|
# Posted: 7 Feb 2025 01:55pm
Reply
My plan for this year is to build a 10x16 cabin in the woods. I originally wanted to build it on 6x6 posts but have learned that may not be the best idea so I am adjusting to build on 4x8x16 concrete blocks. My question is, what type of gravel is best to be placed under the blocks?
Crushed stone/drainage rocks? All purpose concrete gravel? pea gravel?
It seems like pea gravel would be easiest to level but wouldn't they be at risk of shifting because they don't "lock together"
Also how deep should the gravel be under each block?
I plan to place 4 blocks under 3 4x4 skids, or maybe 4 blocks under 2 6x6 skids if I can figure out how to get 16' long 6x6 skids into the woods.
|
|
Brettny
Member
|
# Posted: 7 Feb 2025 06:12pm
Reply
You really dont need gravel. It can just collect water in non draining soils. If it was a well draining soil adding gravel wouldnt help drainage. The only reason people use it is to make leveling easier.
|
|
gcrank1
Member
|
# Posted: 8 Feb 2025 11:28am - Edited by: gcrank1
Reply
I used 'crusher run' limestone readily available here; the fines harden up after a short while and couple of rains almost like a soft mortar between the locked in rock.
Ive done it both ways on our sand & gravel 'soil'.
1)Leveling the site and compacting where the blocks/piers will go then right on the ground.
2)Leveling the site and in my case making a compacted 'runner' to put the gravel above grade about 1' deep (finished) and compacting that (tractor and loaded bucket back & forth). Other option to keep a structure closer to the ground is to trench so the top of the compacted gravel is at grade. I used the runner as I used an almost continuous line of silo blocks all the way so the under structure beams sit well supported.
Fwiw, my 10x16 prebuilt 'toolshed' is the No 1, it is the closest to what you plan to build. I can verify it is easier to level the base blocks it you have at least some gravel underneath.
|
|
DRP
Member
|
# Posted: 8 Feb 2025 06:54pm
Reply
The purpose of stone is to spread the footing and drain water. I spoke about the 45 degree angle of load path through materials previously, same applies here.
Fines trap water and lead to frost heave. Use "clear" or washed rock in a rubble foundation. Railroads are a good example, that is clean stone for a reason. The code does have a section on rubble foundations and one of the better resources for a rubble trench is the Superior Walls foundation installation guide.
|
|
spencerin
Member
|
# Posted: 9 Feb 2025 04:56pm - Edited by: spencerin
Reply
I would put the blocks on 2-3" of 3/4" to 1" crushed rock. Don't dig a hole for the rock, rather "mound" it, level it, and compact it for the block. You don't want any water pooling underneath the rock.
|
|
|
