FOUNDATION - 14x16 micro cabin with loft.
 

Hello everyone,

I a building a micro cabin for me and my family. It is going to be in California. very off the beaten path.(no permits:smack)

I need to ask for help on the foundation as the ground is extremely rocky 1' to 2' minus stuff with dirt in between.

What would be my best option for a pier foundation as digging is going to be very difficult.

Also, I plan on using 4"x6"x20' beams on the piers under the 2"x6" floor joist. What is the correct spacing for the piers?

Thank you in advance for your help.

Renome1971

I didn't mention that this cabin will be totally off the grid.

Pier foundation is the easiest. You do need to think about weather and plumbing connections under the building. Also animal problems underneath.

Thank you, Painterswife. Most of my plumbing is going to be a 12v RV application as this is going to be a getaway and not a residence (At least not at this point! :happy: )

I haven't done this type of project before and am looking for suggestions on the best pier type and application. Like "3/4" drain rock then (2) 16" paving blocks with a pier block 4"x4" style to the 4"x6" cross beam."

How cold does it get? Get down below frost line. IF you can dig at all, dig hole, pour a sack of concrete for a pad under ground contact treated 4"x6" post. Can't dig at all and no frost line, what you proposed to do is good. piers 6' apart with a "bracket" to tie post to 4"x6" beam, plywood works good, 1 on each side of center rows, just inside on outer beams to keep everything flush. I would use 4 beams. 2 at edge and evenly space the others. Floor joists on 16" centers, crosswise. Rim joist on end of floor joists, even with outside of beam, gives 1 1/2"of support for the floor joists. 3/4" tongue and groove plywood subfloor. No strandboard. Brackets can also hold a splice together, splice centered on post, so you don't have to haul and handle such a heavy beam. I take you are saying 20', 4' for a porch since cabin is 16'?


They make a heavier 4" thick block that is much stronger than the pavers. May not need rock, if there is not a lot of duff in the soil. Or can remove the top layer....James

Er, how many in your family, and their ages??

7 total, kids are from 7 to 12.

My only comment is to re-think those 2"x 6"
floor joists to at least 2"x 8". I've seen (and
had to replace) a number of floors that have
sagged because someone before me, tried to
save costs and cut corners by using building
material that is too small for the job.
The extra cost is nothing in comparison
to having to redo the work later.
Besides, if there is a crawl space, you'll
also likely want to insulate between them
and depending on how far up in the mountains,
you'll be glad the floors are warmer in the winter.

We do get snow up there. It probably gets (we haven't been there in the winter yet) 0-25F degrees in the winter.

I've seen this as the most common with only 2 beams and inset from the edge? Any thoughts?

That would probably be fine in terms of spacing the beams and piers, especially if you go with 2x8 joists. I would not, however, just set the piers on the ground in an area that freezes.

jwal10 and jtbrandt. I will use the 2x8 floor joists for sure per your advise. I am still trying to figure out the piers due to the condition of the ground.

Thank you again for all the information and ideas!

Renome1971

And? Your gonna sleep 7 people in a 14 X 16 cabin? How many floors?

I have no problem with the 2"x6" floor joists but the outside beams need to be out to the edge, supporting the walls and floor joists, just like a concrete foundation crawlspace. If this was a permanent home or may be later, I would go even 2"x10" for more insulation. Also why I said 4 beams, center 2 spaced out even. 6' spacing between posts for the 4"x6" beams and the space between beams. 16" between floor joists 3/4" tongue and groove plywood glued and nailed every 6"....James

Rake off any sod and loose duff. The ground will be dry after the cabin is built if graded right so the water will run away from the footings. Mobile homes are set up on dirt, just the top few inches of grass and roots scuffed off, 4" thick solid block set right on the dirt, then concrete blocks set on them, another solid block and shims. Same works here....James

One of the reasons for setting the beams in from the outside walls is to keep the piers on dry ground. I still wouldn't use piers set on the ground, but that's just me. Those tend to sink and heave at different rates and then you have to re-level them from time to time. Sometimes they'll pop nails or even break joists if they move too much. But this may not be as big of a problem there as it is where I am.

Another reason they set the piers in like that was probably to reduce the 2x6 span. Going with 2x8 eliminates that concern for a building of this size.

Are there actually places in California with no permits required, or is this just far enough off the beaten path that you can quietly go about your business without worrying about it?

2x6 floor joists on 16 inch centers can span up to 8 ft according to code here in Michigan.

For a 14 foot wide building, an 8 foot span only works if you inset the beams or use more beams as jwal suggested.

Have you considered a rubble trench?

it is going to be tight for sure but this is a get away cabin and we don't always have all the kids. There will be 2 14'x8' lofts for the kids to sleep in.

There isn't anywhere in CA you don't need permits. I am going to try and build it as close to code as I can just in case. It is 50 miles from any town in a small valley. Far enough off the beaten path that it shouldn't be an issue. I plan on prefabing a lot of the cabin and hauling it up there. I only have one neighbor about 1 mile away 3 canyons over.

Due to the condition of the ground (Rocks, rocks and bigger rocks) Digging is extremely difficult. Stem wall or rubble trench unfortunately is not an option :sob:

This is what is confusing. Other sites say this is ok. Is it?

I build all my sheds on them here. Some on top of a raked off building pad with 4" of tamped and watered down crushed rock. Some on the 4" thick heavy block used for mobile home sets. It has gotten down to -15 here but never had a problem under a building where the ground stays dry. I build 12' wide with 3 beams. Good width inside, then add a lean to on 1 side, later. 6' spans on piers and floor joists....James

That'll work as long as you noticed that everything sets on top of gravel. To do it right they would have dug holes down below frostline and filled them with gravel. That would provide a stable base that wouldn't be prone to frost heaving.


WWW

Set it up like a portable shed on blocks.I would look at making it 16 x16 to cut down on cutting and gain a few feet.

I would use stone and mortar. I suspect you have plenty of stone, sand and water on site so then you just need to haul in the cement. A high thermal mass house is very efficient and building a small one like you're describing is pretty easy with masonry. This is how we built our 252 sq-ft cottage which is just barely bigger than your proposed house.

To do our foundation we smoothed the site down to ledge (just a few inches), put down gravel, then a layer of foam insulation and a vapor barrier. We poured a steel reinforced floating foundation pad on top of that. This is often called an Alaskan foundation. Worked great. Easy to do. We then built the house on the pad. The entire house is masonry including the roof which is a ferrocement barrel vault. For hand mixing the concrete we used three small mortar mixers. One for back up and two running at a time for speed. One person operating them, one person doing sand, one person carrying five gallon buckets of concrete and me mortaring and placing the walls and then doing the ceiling/roof.

It took about two months for us to hand built it and close in. Total cost was about $7,000. Heating cost is minimal (0.75 cord of wood/year) and there is no cooling costs. Real estate taxes are minimal since it is small and considered low grade. It is also very low maintenance due to the very strong construction.

We are five people and our small house fits us very well. We spend most of our time outdoors, the interior is for meals, cooking, sleeping, reading, quiet things. We built our cottage in 2005. We love it.

See: http://SugarMtnFarm.com/cottage

Have fun building your house and enjoy it for decades to come!

Cheers,

-Walter

As with most things, harder to do is better than an easy way out. A few days with a pick axe will yield a foot deep trench around the edge of your proposed building. A hundred eighty pound bags of readymix will give you a foundation a foot wide, a foot thick. Add 160 feet of rebar, 1/2 to 3/4 inch thick.
But that isn't what you asked.
Level 8 spots, two rows of 4, 5 feet apart, for each 29 foot beam to sit on. The beams should be 8 feet apart, so your rows of level areas are 8 feet apart. Either male these level areas into the ground or atop the ground. Pour 4 to 6 inches of concrete and set a standard concrete block on it, your beams will set on this. As time passes, add shims between the blocks and the beams. You will have 3 feet of floor past the beams on both sides. You can easily get under it to level it each year. Just do that while you are insulating and adding fresh heat tape to the water line in the fall.

Im confucus? You say 2 lofts, each 14 X8. Put together, that's 14 X 16, the size of the house. IF there going to be 2, as in one above the other, I don't understand why you would only have them at 8ft when they could go the full 16, with a hole in one corner with a ladder up the side.
IF there one above the other, Id REALLY hate to roll outa bed on the upper one lol.

This is essentially how our cottage is. There is a loft over the front and a loft over the back. In the middle we have a cathedral ceiling up to the full ~11' of height. This makes the cottage feel very airy and spacious.

The lofts are short, just tall enough to sit up in on a bed. They are about 6' and 7' long by the width of the cottage. Under the front loft is our entry, dining table and pantry space. Under the back loft is our master bedroom and bathroom with shower, tub, toilet and storage. In between in the full height space is our library, desk, wood stove and kitchen.

There is a railing on the lofts so you won't 'roll out of the wrong side of bed' in the morning. :)

This works out very well. If I had it to do over again I would make the ceiling 1' or 2' taller to give more height in the lofts and put dormers on facing east and west (our cottage runs north south) but it is okay as it is.

-Walter

I'd rent a backhoe and a rock drill and dig the holes for the piers. Looks like you've got limestone -- it generally breaks up easy enough. (We have terrain similar to what you've got here -- nothing is flat, and everything is rocky. It's a pain to deal with, but not insurmountable with the right equipment.) Home Depot rents small backhoes that will get the job done. Or, in a remote area, a neighbor might have one and be willing to do the job for you for a bit of $$$.

You want to get below the freeze line, or you'll have issues when the ground freezes.

While you have the backhoe on site, you can also do any other needed work -- drainage improvements, pulling out dead/overcrowded trees, trenching for water/sewage lines, flattening a pad for parking, improving the access road, etc.

If you have issues with clay soil, I'd bring in a few loads of gravel at the same time and spread it around parking areas and around the pad for the cabin. Makes things much more livable.

The upper section of the cabin is going to be 14x20. 4' will hang over the front door. This is a basic plan as my foundation may change the overall end result.

Walter, that sounds amazing and almost identical to the plan I have and I would love to see pictures of the finished cabin if you wouldn't mind sharing?

A stone and mortar house would be the best. But I am not a mason and am a lot better with wood than rocks :). This whole project is going to be done by just my family. But I do have a sh*t load of rocks ;).

This is the site where we would like to build. As you can see it's a little rocky. We staked it out to look at elevation and make sure this is the spot.

We had visitors this trip, some good and some bad. The good ones posed for a picture. The others stung my Ridgeback bad enough we had to give her Benadryl.

Any good tricks for getting rid of yellow jackets and wasps?

Here are a few snap shots of the ground and where we would like to put the cabin.

As you can see we have a large amount of rocks. But I do agree, hard work pays off!

We also had visitors to our property.

#1 Campers that came in and burned my wood, cleaned up after themselves (Thankful) and left me a message in front my fire pit that said "HI" in cut pieces of lumber.

#2 Three big black tail bucks in velvet (Pretty awesome).

#3 White headed wood pecker my girls named "Angel"

#4 Wasps and yellow jackets :grump: they stung my Ridgeback so bad I had to give her Benadryl to keep her from seizing. :( Anyone know of a good trap for those things?

I put a chain across the road with a sign to keep people from burning my wood. I was going to leave it open but I would prefer to not have people on my property.

Theres a doz U TUBES showing how to build with rock. After you get your house up and are living there, IF you want to have a garden space, you might dig up all the rock in that area, and use it for to build a shed, or barn walls.

If there are people camping on your land, it might not be far enough off the beaten path to build without permits...those people might get angry about the chain keeping them out and decide to report your cabin. Or they might think it's all good. It's a calculated risk.