How to prepare your family to survive and thrive in todays uncertain world

How To Build A Small Cabin – Preparing The Site and Building The Floor

This is part two of my ‘How To Build A Small Cabin‘ series.  If you haven’t read part one, you should go back and read How To Build A Small Cabin – The Planning Process.

The very first thing I did once I decided how big the cabin would be was to prepare the site.  The site we chose was already relatively flat, and was pretty close to our trailer.  This allows us to easily run power to the cabin and it gives the kids a better sense of security being closer to mom and dad!

When I laid the gravel pad on our new camp site area, I already knew where I was going to put the cabin so I left that area free from gravel.  I used the tractor to do some final grading of the building site, and did some fine tuning with a shovel.  I thought I was doing pretty good, but boy was I wrong…

The Foundation

I thought about a couple different foundation possibilities during the design phase.  What I ended up deciding on is using precast concrete piers with 4×6 pressure treated timbers going between them.  Unfortunately I didn’t take very many pictures of the early stages of the build, so I can’t really show you what I ended up with.  Basically I used four of the piers, inset about 2′ from each corner so that it was well under the corner and the unsupported span of the timbers was relatively short.

Well, getting all four of these piers and the two timbers level and square was a huge pain in the ass.  I spent about four hours on it getting it fine tuned.  I’m glad I didn’t use three piers…I can’t imagine how hard it was to do.  Eventually though I managed to get everything within about 1/4″ of level across the entire 12′ span.  That’s pretty darn good.  Might be a bit overkill, but I wanted the foundation in particular to be rock solid and level.

The Subfloor Frame

Designing the floor assembly was interesting.  I was initially thinking that the foundation timbers would also act as part of the floor assembly, with floor joists hanging off of hangers.  But since I wanted to bring the timbers in from the sides, I decided that I’d build a subfloor frame and simply set it on top of the timbers.

The subfloor frame was made with joists that were simply standard 2×6 dimensional lumber in 12′ lengths.  I put them on 24″ centers and fastened a 2×6 across each end of the joists.  This made a nice frame that was quite stable.  I used metal 90 degree angle brackets to fasten each joist to the timber supports.  Once this was done, the frame was rock solid.

Lesson Learned:  Now I made a mistake in this step that I want to warn you against.  To determine if everything was flush at the ends before putting on the boards on the end, I used one of the boards as a butt plate.  Well, I should have measured instead, because the board I used was warped, and I ended up with a messed up frame that took a long time to fix, and it never got up to my level of perfection!  In hindsight, I would have simply measured from the timbers to make sure everything was correct, and trusted my tape measure instead of the board.

The design of the floor looked like this:

The Subfloor

Now after the floor frame was done, I was ready to put on the subfloor.  Using my handy dandy reference manual I determined that my minimum thickness for the subfloor was 3/4″ plywood.  My local builders supply store had delivered me some awesome tongue and groove 3/4″ plywood.  Putting it on was pretty straight forward.

I picked one corner to start on and made sure that the plywood was even with the side of the frame, and fastened it down.  My 12×12 floor used four full sheets and one half sheet of plywood.  Compared to building the frame, the subfloor didn’t take that long to put together.

Lesson Learned:  When I put the half sheet of plywood on, I wasn’t careful about the orientation of the plywood.  What most people don’t know, and what I completely forgot about, was that plywood still has a grain.  The orientation of the half sheet was such that the grain was with the joist run, instead of perpendicular to it.  It bows now a bit when you walk on it.  Ugh.  At least it’s only on one corner, right?

Here’s a picture of what the floor looked like when it was almost done:

A Final Note … Short But Important!

By the way, if you decide you want to build one of these yourself, I HIGHLY RECOMMEND buying a book called The Graphic Guide To Frame Construction.  Even though I’ve never built anything like this before, just using this book I was able to pick the right materials, decide on the right spans and distances between structural elements, and so on.  Even if you don’t plan on building your own cabin, I think this book belongs on every preppers bookshelf.

In our next installment, we’ll talk about the walls!

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4 Responses to How To Build A Small Cabin – Preparing The Site and Building The Floor

  1. Squaring the piers shouldn’t be that difficult. Did you string line everything first? If you create two parallel lines of strings a couple feet past your pier centers you can then square the perpendiculars off them using the Pythagorean Theorem, or as we simple minded carpenters call it, 3-4-5. Offset the perpendicular a couple feet also. This way your stakes remain in the ground even if you have to pull the lines off, allowing you to re-string for making measurements.

    Using a builders level, or a really straight board, you should have been able to level up the Sonotubes easily, also. Dig your hole so that the tubes will slide into them. Build 2×4 boxes to sit on the ground at the top of the holes sized for the Sonotubes to just fit inside them. Set your first pier to height, plumb and level it. Secure it to the 2×4 box you’ve built and brace it. This is your point of origin. You should be able to then set your straight board on top of that tube with a level on top of it and set your other tubes to the same height by raising them to the board. Just screw them into the 2×4 box to keep them at the right height and plumb and brace them. Always work from your original pier when doing this. If you measure from different piers small mistakes will magnify themselves.

    Did you put steel in your piers? Did you bell the bottom of the holes to create footers?

    When you set your beams you can measure off the string lines you used to square the foundation. From this point on, your beams are level and square and they become your new benchmark. Everything works from them for framing the floor.

    Did you use hurricane clips to join your joists to the beams? They’ll keep the building from lifting in a storm.

    And learn to trust your tape. Math never lies. Constantly check for square and level. Never move on to another step if you haven’t made absolutely sure that everything is square and level. You may not notice it so much now but when you start cutting rafters all the little mistakes will magnify themselves in a truly frightening fashion. It sucks to frame a roof on a crooked building when you know what you’re doing; it’s damned near impossible to make it right if you don’t.

    Take your time and try to always think ahead of yourself. Framing is like chess and the building is the master. You have to out think it. One thing to keep in mind as you move onto framing your walls. Make sure your studs are stacked on top of your joists. This makes for a better load transfer from the roof and it also makes it a whole lot easier to move mechanical components and anything else through the framing because you’ll have the entire 22.5″ to play with.

    Have fun. If you have any questions e-mail me and I’ll try to answer them as best I can. I’ve been a carpenter for over 30 years now and I’m learning something new on every job still.

    • Yeah, getting everything squared wasn’t hard, just time consuming and a pain in the butt. As you noted, the key is to get one corner perfect, then work off of that. It was illuminating how far off of level the site itself can be even if it looks pretty darn good.

      Since this is a glorified shed, we used precast square concrete piers (the kind you might use for a deck) … if it was a bigger deal, we’d have poured a slab.

      We did use the hurricane clips. Two on each side for a total of two per joist … yes, it’s overkill, but it is what it is.

      As far as framing a roof on a crooked building, well, you’ll get a laugh out of my roof post when we get there!

      Thanks for the comment, Tom!

  2. Your post came in this time Rudy, and its a good one…I love articles that give me imformation on stuff I dont know about…..Thanks, Darrell

  3. Thanks Rudy….what i like about your posts is that you are so real and honest about what you do and don’t know. I really like the attitude that one can learn to do things and do things right and correct. In theory it seems so easy, but in reality experience is much different.

    Tom, having built stuff myself, i really agree and underline your principal of always checking plumb and square. I once had a small structure and by the time the rafters were going up…..i was over 3″ off!! LOL….well we got it done and we fixed it….but it just needed some simple checks earlier in the project!

    Keep em coming.