Aggregate piers - Small Cabin Forum

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Small Cabin Forum / Cabin Construction / Aggregate piers


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Heyd Member	# Posted: 19 Jan 2024 06:28pm - Edited by: Heyd Reply https://geohydro.com/aggregate-piers-filling-gap/ https://www.researchgate.net/figure/Rammed-aggregate-pier-construction-process_fig2_2 73748893 What do you think about this method for building piers? Have you ever seen or constructed these before? How do you think they would fare against frost heave? I had the thought to build them surrounded by 6 inches of rammed gravel to protect against horizontal ice lensing grabbing on to them. Your thoughts?

spencerin Member	# Posted: 19 Jan 2024 10:35pm Reply Are these basically pits filled by compacted gravel to grade?

Heyd Member	# Posted: 19 Jan 2024 11:25pm Reply ^ yes or alternatively small cinderblock-sized boulders stacked on top of eachother

Steve_S Member	# Posted: 20 Jan 2024 06:01am Reply Honestly, if you are going to do piers, I wouldn't make ANY compromise that will likely come back to bite you hard... I would suggest you seriously consider using a Bigfoot base for piers. These are available all over North America and many Big Box building supply houses have them in stock. https://www.bigfootsystems.com/index.htm

Brettny Member	# Posted: 20 Jan 2024 06:50am Reply In clay soil those would fill with water and be worse than blocks on the surface.

spencerin Member	# Posted: 20 Jan 2024 12:33pm Reply If one is going to do all that digging and filling in, might as well do sonotubes. And, I'm not even sure it'll be cheaper than sonotubes. Aggregate isn't cheap. Sonotubes will likely be more reliable in the long run, too.

ICC Member	# Posted: 20 Jan 2024 02:15pm - Edited by: ICC Reply A quote from the first link... "Although in many cases aggregate piers can be used successfully, there are instances when aggregate piers are simply not a good match for the site subsurface conditions. Forcing the use of aggregate piers on the wrong site can cause considerable construction schedule delays and cost overruns. Knowing when to deploy aggregate piers, and when not to, can make or break a project. " Sounds like an engineer's evaluation is required. Once an engineer is involved I think a full perimeter concrete or concrete block foundation is likely better and you don't need an engineer for that as methods are prescribed in the codebook. Quoting: Heyd I had the thought to build them surrounded by 6 inches of rammed gravel So a rammed aggregate pier surrounded by 6 inches of rammed gravel. Aggregate is crushed stone with angular edges and gravel is natutrally rounded stone with smooth edges. Right? I fail to see the practical difference as described. I have seen rammed aggregate piers used in sandy, silty soil in an earthquake zone. They made a large grid of multiple rammed aggregate piers. The aggregate spreadout as it was compacted. Then a monolithic concrete slab was poured over everything. The concrete and steel-framed building was constructed upon that. How would you connect your cabin to the rammed aggregate piers to provide lateral and uplift resistance? -izzy

Heyd Member	# Posted: 21 Jan 2024 05:16am Reply Quoting: ICC So a rammed aggregate pier surrounded by 6 inches of rammed gravel. Aggregate is crushed stone with angular edges and gravel is natutrally rounded stone with smooth edges. Right? I fail to see the practical difference as described. My apologies for not making myself more clear: my thought was to do this with roughly discoid-shaped boulders the size of a CPU, not aggregate.

spencerin Member	# Posted: 21 Jan 2024 02:10pm Reply Why are you wanting to use this method? What are the dimensions (L x W x H) of the structure you're wanting to build?

Heyd Member	# Posted: 21 Jan 2024 05:35pm Reply ^ there's no concrete supply where I'm building and honestly I just find the idea of using so much concrete for a small cabin foundation to be absurd. As for dimensions: cabin would be 10Ã—12 or 12Ã—12.

spencerin Member	# Posted: 21 Jan 2024 07:51pm Reply You don't need to do all that work for a 12 x 12. Do block piers on top of a properly graded gravel pad for each pier.

gcrank1 Member	# Posted: 21 Jan 2024 07:57pm Reply I have used 'silo block' as the ground pads for two cabins bigger (1st in '83-'84) than yours with NO issues.

Brettny Member	# Posted: 21 Jan 2024 08:55pm Reply Cmu block right on the dirt for a 12x12. Level useing more concrete blocks or Pat wood. Dont need to over think such a small building.

Tim_Ohio Member	# Posted: 22 Jan 2024 08:35am Reply This, thumbs up. Quoting: spencerin You don't need to do all that work for a 12 x 12. Do block piers on top of a properly graded gravel pad for each pier.