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lapsmith
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# Posted: 6 May 2023 05:21pm
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Hi, newcomer here. I am just getting started on two 16x24 cabins. I have a few basic questions about the foundation.
Around here (Houston area), everyone seems to use concrete blocks to keep their sheds and small buildings off the ground. We don't really have a frost line. But I want to get the floor joists about 3 feet off the ground since there is a creek nearby which may overflow. Is there a way to stack a bunch of blocks together that would work? What other inexpensive options are there?
If I do go with blocks, do I need gravel underneath? Is the purpose for frost heaving, drainage, or something else?
Thanks,
Tom
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frankpaige
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# Posted: 6 May 2023 08:20pm
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Quite a few options out there. I am sure that more experienced builders will offer some ideas.
But! Do not go “inexpensive “! You are putting big money on that foundation.
You want to enjoy those cabins. Not spend time and more money redoing inexpensive.
Have fun, enjoy those process
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lapsmith
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# Posted: 6 May 2023 09:32pm
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Good advice. I won't cut corners, especially on the foundation. But if one way is as good as another I'll pick the cheaper route. I was just looking at a friend's 40 year old mobile home and while the roof is bad, the concrete block foundation looks fine.
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gcrank1
Member
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# Posted: 6 May 2023 10:13pm
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Fwiw
Ive done my own share of 'wish Id of done that better' and seen worse than Ive done
and we get quite a bit of new members asking about their older cabins with 'foundational issues'.
Its looking like the moral is,"overbuilding at the bottom has no downside".
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lapsmith
Member
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# Posted: 6 May 2023 10:42pm
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Copy that. So what would be considered over building? i've read that posts in the ground are not a good idea. One other thing I forgot to mention. It would be nice that whatever I do doesn't preclude me from moving the whole building at some point in the future. But I'm wondering if those two desires are mutually exclusive.
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frankpaige
Member
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# Posted: 6 May 2023 11:45pm
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Nothing is impossible if you got the $$
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Brettny
Member
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# Posted: 7 May 2023 06:58am
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What does code allow in your area for a foundation?
A 3' high stack of blocks isnt going to be the most sturdy thing if you dont mortar them and fill the centers. They also need something solid like a 4-6in deep slab to sit on.
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Aklogcabin
Member
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# Posted: 7 May 2023 10:20am
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I have cedar posts under our 16x24 log cabin that is 3' off the ground and no problems. Has gone through a 7.2 earthquake with no issues. And gets loaded up with several feet of snow.
The cedar poles were used utility poles. And it is doing great. In fact I checked it with a level last time out. I went 4' deep because of our frost.
Put poles in and cut a shoulder out on the top. Bolted a 6x12 beam on that sits solidly in a shoulder cut out.
I was able to dig the holes with a gas power auger. A bit of gravel in the bottom and I used ready mix cement to backfill.
I also went with 10' tall walls so we could have an upstairs. Really nice to have the space
East side
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West side
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Kitchen
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Upstairs
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lapsmith
Member
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# Posted: 8 May 2023 10:51am - Edited by: lapsmith
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Fortunately, I live in an unincorporated area and there are no building codes. But that also means I have to come up with something of my own design that will last.
How would you orient the blocks? The easiest would seem to be with the holes vertical and maybe add rebar down each hole and fill with concrete.
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lapsmith
Member
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# Posted: 8 May 2023 11:02am
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Quoting: Aklogcabin I have cedar posts under our 16x24 log cabin that is 3' off the ground and no problems. Has gone through a 7.2 earthquake with no issues. And gets loaded up with several feet of snow.
Great looking cabin! I like the way you notched to cedar posts. Utility poles will probably last forever. and 10 foot walls are a great idea, I might do the same.
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Brettny
Member
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# Posted: 8 May 2023 12:16pm
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Quoting: lapsmith How would you orient the blocks? The easiest would seem to be with the holes vertical and maybe add rebar down each hole and fill with concrete
I would prob do 2 facing north/south, then on them face them east/west and fill the cores.
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lapsmith
Member
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# Posted: 9 May 2023 10:02am
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Do you mean like the shape of a cross? Or do you mean two side by side then two more on top but rotated 90 degrees?
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Brettny
Member
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# Posted: 9 May 2023 11:45am
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Useing 8x16 blocks you would end up with a 16x16 pier.
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lapsmith
Member
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# Posted: 9 May 2023 12:29pm
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Ok, got it. Thanks!
Regarding my other question, what is the purpose of gravel under foundations? If there is essentially no frost line, is it necessary?
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Brettny
Member
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# Posted: 9 May 2023 03:21pm
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Not sure. Prob to keep things a bit cleaner. If you plan on skirting the place I would do gravel and possibly a vapor barrier.
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Aklogcabin
Member
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# Posted: 10 May 2023 09:50am
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Gravel allows for water to disperse under the footings or pilings. And compaction of the soil under.
As Northrick has explained. Frost hydrologicing, heaving, needs moisture. So less likely to have hydrilocing happening with some gravel to disperse the water.
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Brettny
Member
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# Posted: 10 May 2023 10:38am
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I would hope you wouldnt have any surface water under your cabin due to proper site work and drainage. So the gravel technically shouldnt do much.
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gcrank1
Member
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# Posted: 10 May 2023 08:58pm
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If I had to be concerned about heaving my site prep would be to get a shedding membrane beneath, peaked at the center so it would drain outward to 2-3' beyond the structure, then cover with gravel.
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lapsmith
Member
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# Posted: 10 May 2023 11:49pm
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Not planning on skirting the crawl space other than with lattice or something non structural. In which case I don't think I need a vapor barrier.
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lapsmith
Member
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# Posted: 10 May 2023 11:54pm
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Quoting: Aklogcabin Gravel allows for water to disperse under the footings or pilings. And compaction of the soil under. As Northrick has explained. Frost hydrologicing, heaving, needs moisture. So less likely to have hydrilocing happening with some gravel to disperse the water.
I must have missed Northrick's post. From what you're saying,, snce we don't get much frost here, seems like gravel is not necessary.
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lapsmith
Member
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# Posted: 10 May 2023 11:55pm
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Quoting: Brettny I would hope you wouldnt have any surface water under your cabin due to proper site work and drainage. So the gravel technically shouldnt do much.
No surface water as I will first add some fill dirt to make the area under the cabin higher than surrounding soil.
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lapsmith
Member
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# Posted: 11 May 2023 12:01am
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Quoting: gcrank1 If I had to be concerned about heaving my site prep would be to get a shedding membrane beneath, peaked at the center so it would drain outward to 2-3' beyond the structure, then cover with gravel.
No heaving here, but the clay soil in this area does expand and contract with moisture levels. It cause slab foundation cracks which is a good reason to use blocks, IMO. Dry wall can also crack so I may use T&G instead.
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