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darren
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# Posted: 12 Jun 2015 10:57
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Has anyone built an A-frame of roughly 16x20 on just deck blocks?
Seems like pouring a cement pad might be overkill.
Looking for thoughts/ideas on this.
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leonk
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# Posted: 12 Jun 2015 12:29
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do a search here.
depends on location (climate), soil and budget
either go below frost level or stay above ground with the foundation
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bldginsp
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# Posted: 12 Jun 2015 17:06 - Edited by: bldginsp
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I built a 14' x 14' dirt floor A-frame to keep the snow off my pop-up tent trailer. I just put precast piers (deck blocks?) on dirt with no added concrete. I put down six on each side, angled them to the roof angle, and put a 14' 4x6 PT across the six on each side. Site cut pole rafters sit on the 4x6s. I could post a simple CAD drawing of you want to see it.
It's a pretty down and dirty way to build a building, and I would only do so for a dirt floor storage shed that doesn't need to last long. As it is it's been 7 years and the building is fine. We have a 18" frost depth here and I see little evidence of ground heaving, which would screw up a building like this if it were serious. One reason I used so many piers was to balance out the forces as much as possible. Won't help with serious heaving. Probably work fairly well in the southeast, but not in areas with severe cold and deeper frost.
Pouring a good concrete foundation is never overkill if you want the building to be useable 20-30 years on. Getting footings to proper depth is the key.
Match your methods to your needs
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Steve_S
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# Posted: 12 Jun 2015 17:34
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Darren, seeing your in the Yukon, you will have frost heaving unless your building on bedrock. The Alaska Slab (Frost Protected Slab) is likely quite common around you. If your going to use this year round, you'll certainly want to have an insulated floor. Think about the worst weather you've seen and plan for that + a nice margin. As you saw last winter, the weather is becoming extremely fickle the further north you go.
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darren
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# Posted: 12 Jun 2015 18:54
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bldginsp
Simple CAD pic would be awesome.
Steve_S
You're right. I'm in the Yukon. Frost heaving is a real issue here, and an insulated floor is a must! We've seen -45C in the last few years.
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bldginsp
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# Posted: 12 Jun 2015 22:37
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I'll get to it over the weekend, Darren. Sonotube piers are your best bet short of a slab or full spread footing. Maybe you can adapt my simple design to your needs.
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Steve_S
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# Posted: 13 Jun 2015 12:03
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Darren, a thought occurred that it may be possible to use frost protected screw piles like those from Postech Thermal Piles or technometalpost
Some are usable in regions such as yours and may be worth looking into. I have used simple versions of those for a deck and they worked a treat and were quite reasonable for the 5' versions... If memory serves they were $60 ea at the time for the 4" version...
It appears that the Thermal ones need some machinery to do the install but there maybe a DIY option available. Check around your area to see if anyone uses them or carries them and see... Really depends on the soil / bedrock depth that your working with or if your really up there if you have Permafrost issues which also changes the game up somewhat.
I've done work in Nunavut and most places I saw in Iqaluit and other communities, everything was pretty much on piles/piers driven into the permafrost or to bedrock depth.
What the heck, can't hurt to consider options.
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bldginsp
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# Posted: 13 Jun 2015 15:56
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Darren- here's the CAD of my basic A frame and a photo. If you don't want to pour any concrete, one thing you could do would be to dig holes beneath each pier and pour in either dry concrete or gravel. Both are non-expansive. The concrete will harden, not to max strength, but plenty to support a small building like this. If your roof is 60 degree pitch you will have very little snow downbearing on the building and foundation, but you will have lateral snow pressure if it gets deep against the roof sides. That's why the horizontal ceiling joists are critical for this, and the connection to the piers. I used the strap type of pier, that has metal straps embedded in it, and I nailed those to the 4x6. Also I strapped the rafters to the 4x6. Nail connections are not enough. Note that I put one brick on top of each pier to lift the 4x6 a bit more off the dirt.
I can see Don P squirming in his chair right now. I greatly appreciate your cautious approach Don. And I repeat- I would not use this construction method for a habitable structure, only a small dirt floor storage shed. But if Darren wants to do otherwise, that's up to him.
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Don_P
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# Posted: 13 Jun 2015 18:47 - Edited by: Don_P
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How could you tell 
Use floor joists rather than dirt to create the tie. It puts it in the right place to restrain the rafter thrust and gets the load back to vertical.
Another way is to build a timber sided "sandbox" larger than the structure by Several feet and fill it with gravel, levelled. Then 6x6 skids and build the triangles laying on the skids, tip up and connect. The bottom chord of the triangle becomes the floor joists. A few mobile home anchors from skids to ground for uplift. Depending on frost depth, depth of the sandbox and soils you'll be riding on top of the frost.
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bldginsp
Member
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# Posted: 13 Jun 2015 19:06
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I wonder, when Noah built his ark, what he was thinking about uplift.
You could say he had a very uplifting experience.
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