Hot Topics: Small Cabin on Stilts

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Original Post: Small cabin on stilts

Nick Hriscu - Member

Hi! I am not sure if this is the right forum topic for my questions and I apologies for that. I am building a small cabin on stilts this summer and need some advice. I'm planing to make it 13x13 ft at 9 ft from the ground. It will be off-grid, the top I'll use as summer fishing cabin, the bottom as working shed. My question will be:

What dimensions the stilts should be? I was thinking about 4 on each side, 6x6. The dead weight of the cabin consist in a small fireplace (120 pounds) and a couch.

How deep should I dig in the ground? I was thinking to dig about 3 ft add gravel to the bottom, get the stilts in place and pour concrete around it. Does that sounds like something that might last 10 years or more?

The little cabin will be placed right next to a pond on solid soil but it gets a little wet in the spring. No permafrost and no clay. The surface is flat. Frozen line about one feet ans a half.

Any advice from anyone would be considered and appreciated.

marksr - Forum Topic Moderator

Welcome to the forums Nick!

What depth is your frost line at? why 13'x13' that would incur waste if you buy dimensional lumber which would be 8',10',12, or 16' in length.

joecaption - Member

Where are you located?

Going to get a permit to build this?

A 2 story building and only set the post 3" in the ground

Vermont - Member

No indoor plumbing, I presume?

I once sold a place (as a Broker) that had footings; but whose toilet was pushed up about 2 feet by frost every winter. Children would need a ladder to mount the throne!

Msradell - Member

As mentioned previously your post will definitely need to go below the frost line and probably deeper depending on the type of soil you have. The wind is going to put a lot of pressure on the posts and the rest of the structure. I think you are going to need something bigger than the 6x6s you talked about and they are going to have to go quite deep so they don't tilt. You probably also are going to need to put some cross bracing between them.

Is there any reason you are putting it up on stilts instead of a larger structure on the ground? It would certainly be simpler and you'd have fewer risks if you didn't put it up that high on stilts.

Bud9051 - Member

Hi Nick and welcome to the forum. Sounds like fun, but all of the comments so far seem appropriate.

Are you talking the top of the cabin will be 9' above the ground or the bottom of the cabin. If it is the bottom, then that is a very tall structure for just 3' in the ground. Mother nature would easily tip that over.

Nick Hriscu - Thread Starter

Thanks everyone for your reply!

I mention 13' because I can have custom lumber but I might just go with 12' to make it easier.

The frost line is 2' deep.

The location is West Virginia. No permit and I am not trying to get a builder for this. This will be 100% my own project (is a dream I am fulfilling) but I am also trying to make as good as possible, learn something from it and maybe enjoy it afterwards.

The cabin was first envision as an open shed by the pond, so I can work and go fishing from it when it rains. Then I decided to go a little higher with the roof to make room for a living space.

This is a silly question, but all those tree houses with the additional posts only 2' into the ground, how come they are not tipped out? I was thinking to dig deeper, money is not necessary a problem but safety and DIY is.

So would you go with 8x8 posts, maybe 5' in the ground? Would it be better to go with metal posts instead? Although I kinda hate the look but I guess I can mask that in wood. Again, is a 12x12' with 4 posts each side (so sitting on 12 posts total), I was thinking this is more that enough .. 2 sides of the lower level will be blocked with wood siding. Also the lower lever will have some sort of flooring (like a covered deck).

I might consider adding some plumbing and just drain the pipes out at the end of the summer to make sure they don't freeze.

This is something similar to what I want to achieve: just take away the little thing at the very top of the cabin and add a wood deck at the lowest level; it will also be on a flat ground.

Bud9051 - Member

If you search, there are many examples of homes on stilts, I guess the hurricanes are getting the message through. But the times I have looked into that option they all seem to start with significant support columns extremely well secured into the ground. My guess would be at least 6' and lots of cross bracing. But I'm not an engineer.

chandler - Former Member

As Bud mentioned, a house on stilts is, in essence, a parachute waiting on a good wind. Is the 9' necessary, or can you have walls?

Nick Hriscu - Thread Starter

I edit my answer, it will have cover on 3 sides so it will be opened only toward the pond. One side wall with wood siding, another one the stairs also with wood siding, the third is going to be a massive fake rock formation with waterfall and the forth will be the "lake view".

Nick Hriscu - Thread Starter

Thanks Bud. I will fallow your advice except that front view side, I just cannot add bracing there, it will take the all charm away. Would you think 8x8 wood posts would be enough or would you go with something else? Please see my edit post below.

Bud9051 - Member

This sounds like a cabin in the woods beside a lake, but that doesn't eliminate building codes. I have a camp lot next to a lake which I will hopefully build on and although well away from the cities, there are codes, especially for anything next to a lake. I will have an approved septic and the cabin will need to meet the codes for an unorganized town (state controlled). Whether an outhouse would meet your bathroom requirements is one question, but they usually object to grey water flowing into a lake, or ocean wherever you are.

As for the engineering, I can't say what is required.

Nick Hriscu - Thread Starter

I will get an ecological septic tank and I have a good well on the premises. The place is a 4 acre land with a half acre pond in the middle, no other top water stream but I will be careful about the under ground water flow. At this point I am mostly looking at what my wood material would be and I got stuck at those wood posts

Bud9051 - Member

Have some experience building high off of the ground and you will need to give some consideration to where you will stand when building that cabin. If you plan it right the temporary perimeter working area can be recovered to reuse as the wood platform at the bottom.

I would go deep, 4 to 5' on the front two posts where it will be open with no cross bracing. The others will have wall covering which will help stabilize it or hide the needed cross material.

I searched "building plans for a cabin on stilts" and saw many examples and I assume you could find something similar and even purchase a set of plans. That should provide a starting point. But soft soil vs rocky well compacted soil will require different support. Have you tried digging down in that area to see what the soil looks like or if you hit ledge?

ray2047 - Member

The frost line in Arlington VA is 24 inches* so I'd say rent a concrete mixer and a dirt auger. Set concrete piers three feet deep (guesstimate) then use Simpson Strong Tie brackets to fasten 6x6s to the concrete piers. Not an expert but that is my best guess. The experts here can modify my idea.

Nick Hriscu - Thread Starter

Bud, that is soft soil. I've been looking online at different house on stilts plan but they all seems to be too big for what I want.

Ray, that would be my second choice, but why is better to have concrete piers 3' deep vs wood posts in concrete 5' deep. I would have think the second is steadier.

Bud9051 - Member

If you have soft soil then you should also consider a footing at the bottom to spread out the load.

IMO, the advantage of concrete columns up to grade is they will last much longer, concrete loves moisture.

Can you get a backhoe in there or will all digging be by hand?

Nick Hriscu - Thread Starter

all hand work, digging, mixing the concrete ... I've seen some getting the post in a plastic bag before pouring the concrete around the post. Building the house from the platform up wouldn't be an issue, I am trying to find the best solution for lifting it up from the ground, without unnecessary work or waist but with more than average safety precautions. Like if you will say 8x8 posts minimum I could go to 10x10 just to be sure... or maybe I am overthinking this. This is a better example of what I want to achieve,, without too many bracing, what could those post be? maybe 10 or 12'' ?!? And as I can see they are just set into the ground somehow...

Bud9051 - Member

I would guess those are 8x8's with 4x6's on the diagonals. Remember, these will be pressure treated so at 14' each will weigh about 250 pounds, but it will feel a lot heavier. A 12x12 will double that.

A generator for the drills and saws. Lots of galvanized bolts, plus any other fasteners that attach to any PT wood will need to be rated for that.

"I am trying to find the best solution for lifting it up from the ground, without unnecessary work or waist but with more than average safety precautions." What is it you are planning on lifting, the deck for the 13X13 cabin?

ray2047 - Member

Missed you want to go to five feet. But with soft soil that would be better then flair out the bottom. Placing the post in the concrete does not protect it from moisture and even treated eventually rots. Imagine the headache of replacing a rotted post buried in concrete.

Nick Hriscu - Thread Starter

The lifting was referring at the cabin, the deck can be as low as it can, I just mentioned it because I imagine that the deck can improve the stability of the structure a little bit.

After a lot of search and thanks to your advice I decided to go with a post and pier system, with concrete piers 5' deep and treated posts 8x8, 9' long. On top I will have like a platform and build the little cabin on it. Two sides will have wood siding, one side will have fake rock wall and one side open. I will not start the project until end of April so I can still take any advice you might have and I am planning to add pictures when is done in case others might run into the same situation. Thank you all!

Wirepuller38 - Member

Where do you live in West Virginia? I lived in Lewisburg for 5 1/2 years during the 1960's.

I agree with what Ray said in post #15. Use plenty of bracing in the three closed in sides of the lower level of the building. Good luck with your project.

Bud9051 - Member

To maintain the clear opening across the front you will want a good header at the top of those front support columns. Combine that with a couple of substantial angle brackets and you can retain a lot of rigidity against side to side sway.

You will also want some liquid treatment for the places where you cut the pressure treated wood to maintain its resistance. Not sure what is recommended for the modern PT material. Note, there are also different grades of PT. Something to look into.