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Tiziano
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# Posted: 14 Jan 2020 03:29pm
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Quoting: OwenChristensen Two skids because three will cause differential lifting. Two might cause a slight tilt, but no damage to the building.
Old thread. Sorry. But I just came across it and wondering about the number of skids. My design (12x16, 10' high ceiling, clay soil, west of Minneapolis) was going to use 3 skids.
If 2, how does one keep the floor from bouncing when walking on it?
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ICC
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# Posted: 14 Jan 2020 06:52pm - Edited by: ICC
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Skids on the bottom (running lengthwise), then floor joists across them running side to side. Those are sized to the span. Then the subflooring laid on top of the joists.
#2 grade, 2x8 of most common species, on 16" centers should suffice.
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Tiziano
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# Posted: 15 Jan 2020 07:11am
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Thanks.
Is there a reason to not run the joists between the skids instead?
Maybe this should be a new thread?
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Brettny
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# Posted: 15 Jan 2020 08:16am
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Ease of build would be one of them. A joist laying on the beam is going to be stronger than using a joist hanger and much cheaper. You can bring in your beams from the walls too and make the span a bit less.
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Brettny
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# Posted: 15 Jan 2020 08:20am
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Quoting: JJHess Cutting holes and going from the inside is one way. We can also install right beside the structure and push the pile under the structure. We just have to relieve a little dirt from the back side so we can push it back. Installing from inside is usually not that difficult. The attached pics show a cabin with a tile floor. They just pulled up a few tile, cut a hole and when we were done they put it back together. New wood beams were slid under the cabin and jacked up to support the floor.
What are your spans and wood size now? That looks like a major job now and prob saved less than $300 when the place was built. Also why a little crawl space may not matter at build time but could be a life saver when/if you ever need to do work down there.
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Tiziano
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# Posted: 15 Jan 2020 02:16pm - Edited by: Tiziano
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Quoting: Brettny A joist laying on the beam is going to be stronger than using a joist hanger . . .
Hmm. But if the joists were laying on the ground like the beams, then there's no span to worry about. But I'm simply guessing.
Been studying frost proof shallow foundations and see that buildings built upon them need to be heated in the winter for the foundation to resist frost.
With that in mind, I wonder if the beams and floor joists were one unit laying on the ground* (and insulated in-between the joists), might that not help minimize frost heave as good or better than a fpsf?
*Assume a prepped crushed and tamped ground surface, GC lumber for beams and joists, site slopes away from building in all directions.
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NorthRick
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# Posted: 15 Jan 2020 04:40pm - Edited by: NorthRick
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Quoting: Tiziano Hmm. But if the joists were laying on the ground like the beams, then there's no span to worry about. But I'm simply guessing. Been studying frost proof shallow foundations and see that buildings built upon them need to be heated in the winter for the foundation to resist frost. With that in mind, I wonder if the beams and floor joists were one unit laying on the ground* (and insulated in-between the joists), might that not help minimize frost heave as good or better than a fpsf? *Assume a prepped crushed and tamped ground surface, GC lumber for beams and joists, site slopes away from building in all directions.
You'll spend more time and money preparing a frost resistant gravel pad and having to use pressure treated joists and subfloor than if you just make sure the skids are properly supported and only those need to be pressure treated.
I have a 12' x 16' cabin, and while not on skids, it is sitting on 2 beams. My joists are 2x6's and there is a bit of bounce to the floor. I knew there would be and it is not bothersome for us. 2x8's would stiffen things up quite a bit and 2x10's would be rock solid.
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Tiziano
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# Posted: 16 Jan 2020 08:35am
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Thanks.
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rpe
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# Posted: 16 Jan 2020 10:00am
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Tiziano, if you have silt or clay soil within the frost zone, differential freezing will cause the ground surface to heave at different rates. I can see that causing huge issues with floor joists in contact with the ground. At my location, ground heaves 4-6 inches in spots under the cottage in winter, but is highly variable as veins of clay run through the soil in that area.
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Tiziano
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# Posted: 16 Jan 2020 04:22pm
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Quoting: rpe if you have silt or clay soil within the frost zone, differential freezing will cause the ground surface to heave at different rates. I can see that causing huge issues with floor joists in contact with the ground.
Funny you mention that. It dawned on me last night!
I had a Techno-Metal Post estimate awhile back. He said they need at least 6" ground clearance (for the beams) due to differential heaving.
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