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Small Cabin Forum / Cabin Construction / Foundation questions for Bunkie
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# Posted: 26 Mar 2022 09:02

Hello everyone, we are planning on building a bunkie
108 ft2 + Bonus Loft 73.5 ft2 and about 3884 Lbs.
Our main issue is foundation;our location is next to a big creek, not a lot of top soil before you reach a clay layer. Winters are long and this year there was a lot of thawing and freezing,people have suggested Titan screws but they are incredibly expensive. If anyone out there has any type of advice I will greatly appreciate it.

# Posted: 26 Mar 2022 09:45

A few things to know before you start...
- Are you out of the flood areas ?
- Are you intending to build close to ground or off the surface and elevated (may be a good idea) *
- Do you "know" how deep you have to go before hitting bedrock ? Ideally getting to bedrock is best as it shouldn't move.

* This would affect the type of "pile" used even screw piles are chosen for the soils they have to be in. As well this also has to consider raking and how to support the structure to prevent it from twisting on piers.

Screw Piles do work really well in the right conditions and can last a long time BUT they should not be considered "permanent" and that's where this stuff hits the fan... You can get cheaper piles which are painted, then others that are Galvanised and up to Stainless Steel ones ($ ouch). They will ALL have different performance standards and lifecycles and as such very different pricing... Some do require Machinery for installation (even more $$).

Have a look at these sites for more info / options.

I've used Screw Piles from Pylex in the 4" & 6" versions (commercial versions) with great success

!! Note that without machinery it is a challenge AND if you hit a rock/boulder you have to dig it out (even if you have a machine). CONSIDER that if you are on rocky terrain - damned rocks always get in your way....

# Posted: 26 Mar 2022 11:24 - Edited by: gcrank1

Its a bunkie, not a small house. Other than yours will have a small loft the basic foot print is about as big as my ice shanty on wheels.
Id cut trees and brush well back (many dont cut back far enough early on, me included 1st time, level the site and put down flat concrete pads and beams for the structure to 'float' on.
Id also have it high enough to be able to crawl under to provide flow-through air, prevent critters from nesting and be able to jack it up if/when it ever needed re-leveling. My 1st build was like this, no regrets, but our second/current one built by somebody else is too low and I have things I need to do under there

# Posted: 26 Mar 2022 14:41

Floating on beams would be easiest for sure, but would require seasonal re-levelling. Build a stiff structure so doors will open in winter if needed.

I've used commercial galvanized screw piles (3" diameter pipe, 10" diameter helix) for a workshop build. I couldn't get suitable installation equipment to my site, so I ended up augering a hole, setting the screw pile into concrete at bottom of hole, and backfilling with gravel. That keeps the clay and frost heave from messing with the tube, and the concrete slug at the bottom distributes the load to the soil below. I'd consider Pylex for a small deck, but not much more. The ones I've seen are thin wall, painted, and do not have a very substantial weld between the helix and tube. If that weld gives way in a few years, now your structure is just supported on that flimsy little tube.

# Posted: 26 Mar 2022 16:13

Thank you so much for all the helpful advice! Yes we are out of the flood areas and we just looked at these:

to place on a 24 by 24 patio slab/concrete slab plus an Adjustable Deck Support - 10'' - Steel
The site is pretty remote, we are going to be moving everything by ATV and by muscle power. Not sure about being able to do a concrete pad. Agree about the crawl space for ventilation. Our main worry is that the ground will be shifting and we will eventually have to re-level the bunkie. We are a bit nervous as this is our first build.

# Posted: 26 Mar 2022 16:38 - Edited by: gcrank1

I didnt mean 'mixing and pouring' concrete pads, I meant pre-made pads, 36"x36" or so, spaced properly for spans and loads. Many dig a hole, put in gravel, compact it, then pad, etc. Lots of info here and elsewhere.
Fwiw, we used 'solo block' on our 1st build 12x24' c/w 12x12 loft, in '83. Up until 2 years ago (when we left it) I only had to shim it One Time at the support near the middle of the 24' beam by the door (it got to dragging after about 4yrs).
My 8x12 ice shanty was homebuilt by another chap on a little 2 wheel travel trailer frame. Man, did he overbuilt it! It is a heavy hard pull....he only used it the 1st two winters on a lake near home, and he pulled it with a big pickup. I bought it to use as a toolshed/powerhouse; pulled it in (barely) with my suv, parked it, jacked it up off the tires and (ta-da) blocked it levelish with silo block pads, std cement blocks and treated wood scraps. If I ever need to relevel I can get a big hydraulic jack under and shim it.
Your proposed place would be handled in a similar way were I you. Buts thats just me, ymmv.

# Posted: 27 Mar 2022 05:53

Sorry something so small, 10x10ft I wouldnt bother with anything but blocks. 2 runners with 3 blocks under each. Use nice thick runners and floor joists and you will have minimal need to relevel. Where issues re leveling come into play is when you need 3 runners, it can be hard to get to the middle runner. People also like to skimp out and use 4x4 runners and 2x6 floor joists.

I have a 10x14 on clay in central NY and dont have problems with frost jacking or opening the door. No special foundation work was done. Drug the shed in (6x6 runners) blocked it up and leveled. I did make sure any water dosnt go under the building.

# Posted: 29 Mar 2022 10:20

Some might scoff at this lol…Depends on the size of building of course…but for small outbuildings like sheds or my wood shed… I’ve used skids placed on concrete bags. The bags are nice because they’re effectively concrete pads and you can sort of wiggle the skids into the bag to conform slightly and level everything. Then either wet the bag or let nature do it for you. It’s not a perfect foundation and of course the cement isn’t as strong as it would be otherwise If properly mixed but it will harden and you’ll have a nice easy foundation for a small outbuilding. Frost isn’t a problem as it’s a floating pad.

If you need to jack one corner in a few years big deal it’s a small out-building.

# Posted: 31 Mar 2022 16:47 - Edited by: BRADISH

Given the dimensions you're shooting for - i would personally go with a 'less is more' approach here.

I would stick to a very simple plan. Releveling would likely be required, but you're talking about moving something the size of a small pickup truck.

Can you change a truck tire? Then you can certainly relevel this bunkie.

This would lead me to build it off concrete 'pavers'/pads as suggested earlier and just deal with the releveling when it occurs. Cheap, quick, effective. Grizzlyman's concrete sack approach sounds fine too.

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