Yurt foundation…pier and post

 Posted by at 4:10 pm  Yurt Yak
Aug 272010
 

So…you have decided to put your yurt on a crawlspace foundation.  Smart move.

“Of course YOU think its smart, Bob…just because YOU did it, it must be the right way…the ONLY way, right?”

“Go sit in the corner…I don’t have to listen to you yap.  I gave good reasons in the site/foundation section for a crawlspace.  Go back and read it if you were asleep during that discussion.

I promise…just because I have these little discussions with myself does NOT indicate severe mental instability!

I promise, I really do…and it won’t affect the quality of the information here anyway…

Your mileage may vary on that last part.

So lets set some piers.

The first two things you must do is determine what the orientation of your home will be and determine the exact center of the circle that represents the outer edge of the yurt, in my case the center of a 30 ft diameter circle.

First, to determine the orientation of your yurt, imagine the circle is a giant clock and the front door is at 6 o’clock.  Standing at that 6 o’clock point, look along an imaginary line running down the center of your imaginary yurt, and out the backside of the yurt at 12 o’clock noon.

Right about now you are wondering how I know the other side is noon and not 12 o’clock midnight.  Easy…it’s too dark to be laying out pier locations for the foundation at midnight.

OK…now wiggle around a bit, adjusting where you want the front door and exactly which direction you want your centerline running in.  Drive a stake in the spot that locates your front door.

At this point I’ll remind you of two things…first, this is the way I did it and I built a yurt 30 ft. in diameter, and all measurements are based on that 30 ft. yurt.  Second, my platform framing is standard, within code, framing…beam and joist spans, joist spacing, post locations…all of the platform meets code (SBC and UBC) but is NOT the only way to build the platform and have it right…the example given by Pacific Yurts is different, but both give you a strong, safe, code compliant platform in MOST areas of the country.

Due to some local deviations in code adoption and enforcement, be sure to check your plan with your local building department IF you plan to get a permit and will have to pass inspections.  Some people do it that way…some of us don’t.

So anyway…now you have your front door location marked with a stake, and you have eyeballed an imaginary centerline down the middle of the yurt you haven’t built yet.  30 feet along that centerline (for a 30 ft yurt) drive another stake, then directly along that line drive a stake at the mid-point of your centerline.  Build a front and back batter board (Google it) about 5-10 feet from each end of your centerline row of stakes, and pull a string TIGHT from one batter board, directly above the 6 o’clock, center, and 12 o’clock noon stakes, to the other batterboard.

Right here let me give you a little lecture on being precise in your measurements.  If you want your yurt, or ANY structure you build, to look good and be durable, throw away the notion that it can be “almost” right.  Measurements done with a tape measure, like beam lengths and joist spacing, should be within ¼ inch…less if possible.  Measurements done with a level…plumb posts and level beams, for example…should be within ¼ bubble (or less) over a 4 foot distance.

A centerpoint on a 30 ft yurt should be 15 ft from the 6 o’clock and the 12 o’clock locations, NOT 15 ft 2 inches from one and 14 ft 9 ½ inches from the other.

OK, so now you have your front door (6 o’clock) and back door, if you are going to have one (12 o’clock), staked, the centerpoint located, and a tight string showing the centerline located.  Let’s lay out for the other pier/post locations.

First, let’s mark the location for each pier along the centerline.  Call the pier location at 6 o’clock pier 1, and the distance for pier 1 is 0 (zero).  All measurements being from pier one at 0, the rest of the centerline piers are at 4, 11, 19, 26, and 30 ft, for a total of 6 pier/post locations down the middle of the yurt.  Call these piers #1 through # 6.  Remember this for later…(you’ll need it to understand my directions.

You need to mark these points along the center string, but it’s a good idea to be able to adjust the mark when the pier layout is complete to make corrections.  I suggest using fluorescent tree marking tape tied tightly around the string.  It will mark the locations but be movable by sliding it, and it is highly visible.

Note that there is no pier/post location at the centerpoint.  Mark it anyway, just as you did for the first 6 pier locations.  You ALWAYS need to know exactly where the center of the yurt is as the platform is built, layer by layer, pier, post, beam, joist, and to top of subfloor.  It is critical to know where this point is right until the last nail is hammered and the last cut is made on your platform construction, and it useful to know right up until the finished floor is laid well after the platform and finished kit are up.

At each of the pier locations already marked along the centerline, piers # 2, 3, 4, and 5, you need to mark a line representing a beam perpendicular, exact 90 degrees from the centerline, that extends past the edge of where the yurt will be, giving you a “+” sign at each pier location.

There is a more mathematically complicated way to figure the length each side of center for this line, but I’ve forgotten my HS geometry and I’m keeping it simple.  An easy way to have a 90 degree angle for the perpendicular beams is to use the 3-4-5-rule…that is, if the sides of a triangle are 3 ft (or inches, or miles) 4 ft, and 5 ft long, the right angle where the legs join is a 90 degree angle, so…

For the first perpendicular beam (left and right of the #2 pier point), you already have the 4 ft leg…the distance between pier 1 and pier 2.  If you go left in a 3 foot line from the #2 pier, and adjust that lines angle until the remaining line (back to pier #1) is 5 feet long, the angle betweenthe centerline and the perpendicular line will be 90 degrees.  Extend that line outward until it intersects a line pulled from the centerpoint 14 ft 6 inches and you have a pier location for the next pier, #7.  Repeat for pier locations 3, 4, and 5 and you have the pier locations for the left half of the yurt.  Repeat on the right side of the centerline at pier locations 2, 3, 4, and 5 and you have all 14 pier locations pinpointed.

OK…take a break, sip some tea, build your strength…because the next part is the most demanding, physically, of the entire project.

Now, before you do ANYTHING else, re-check all you have done to this point.  Siting, orientation, pier location, EVERYTHING.  To this point changes are easy, but after the next step changes become very very difficult, so be sure everything is right up to this point.

You now have to pour 14 concrete piers 12 inches in diameter and 2 feet long, with 18 inches in the ground and 6 inches above ground level (areas with very cold weather must adjust this figure to allow for the freeze line).

I would suggest renting a two man auger, with a 12 inch auger bit, at your local Home Depot, but if you ate your Wheaties that morning and really want a workout, use a shovel and post hole digger.  Either way, dig a hole 18 inches deep at each pier location, and stick a 2 ft section of tube form (Sonotubes are what I used, also available at Home Depot) in each hole.  Alternatively, after digging the holes, use scrap lumber to build a box 12x12x6 on top of the ground above each hole.

Here comes the really fun part…NOT!!!  Healthy?  Yes.  Beneficial?  Yes.  Economical?  Yes.  Fun?  Not just no…hell no!

You now have 14 voids, 12×24 inches, that must be filled with concrete.  Each hole holds approximately 2 80# bags of Quickrete, and in a large wheelbarrow you can JUST manage to mix two bags, or one hole’s worth, at a time.  So, get the wheelbarrow, a concrete hoe, a shovel, 30 bags of Quickrete (always have a bit extra on hand, just in case), a water hose or other water supply, and a VERY large pitcher of iced tea…get all that ready…and have at it.

What are you looking at me for?  I’ve told you what needs doing…be like Nike…”just do it”…

OK, when you have gotten to this point, with the concrete piers in the ground, the first thing you HAVE to do is…breath a huge sigh of relief.  Almost all the heavy lifting is done, with the exception of one little 30 minute job for you and three…or 10…friends when you are putting the yurt kit up, but we’ll cover that later.  For now just know that those 30 bags of Quickrete you hand mixed and poured was the worst of the whole job.

Side note for those thinking of 30 bags of concrete in horror…I started this project four months after spending two months in a hospital bed, three months after not being able to walk with a walker more than 50 feet without resting, and two months after getting off the walker…if I can do it so can you.  Besides, you’re maybe a fatty like I was and the exercise will do you good…it sure helped me.  If you want to, read about it in the “Rising From the Ashes” section of JuicyMaters.com.

I didn’t take pictures of every little portion of a step in the process.  I could build a lot and photograph some, or I could build some and photograph a lot…I chose the first.

If you read my descriptions, while following the pictures, you will see what every step is, how it was done, and in what order.  If you still have questions, ask them in the comment section.  I do read the comments…every one of them…and answer any questions asked.

Post placement. The FIRST thing you have to do is find the pier that is at the highest point in your pier layout.  This is critical because EVERYTHING YOU DO FROM HERE FORWARD IS BASED ON THAT POINT!  This was easy in my case because the way the land sloped, the highest point was obviously the pier on the far left side of the accompanying picture, but the flatter the land the harder it is to eyeball which is the highest point.  If you have to use a string level, a water level, or, better yet, rent or borrow a laser level, but find that high pier.

Next, decide how high off the ground you want the finished floor at that pier location.  Remember, depending on the lay of your building site the height to the bottom of your doors may be dramatically different from the height of the finished floor at that pier.  I wanted my finished floor no closer to the ground than 18 inches at the highest pier, but that gave me a four foot high front door at floor level, and I will have a deck out the back French doors that is about 7.5 feet off the ground.

So, if I have a pier that sticks out of the ground six inches, and I want a finished floor 18 inches off the ground at that pier, I need a 6×6 pressure treated post that is 17.25 inches high…right?  Not exactly, unless you plan to nail or lag screw your joists to the sides of your posts instead of putting them on top of the posts…a VERY bad idea.  Two bad things will happen:

IF you decide to get a permit and miraculously succeed, the platform will fail inspection and the inspector will make you tear it down and start over…a roughly $2000 mistake.

If you get the yurt up, with or without permits and inspections, the platform will fail, probably within 3-5 years, and you will have a $25,000 to $75,000 (or more, depending on how big and how elaborate the yurt is) pile of rubble ready for the landfill.

Well now, just how tall is the post?  It depends on what you have sitting on top of it.  In my case I had 2×8 joists and beams (7.5 inches actual height), .75 inch tongue and groove plywood sub-floor (please PLEASE don’t cheap out here and use glued up particle board or whatever.  Use REAL PLYWOOD), .75 inch plywood strips (12 inches wide by eight feet long for stripping the floor to place the radiant floor tubing), topped by rough cut 1×6 pine plank flooring (a full one inch thick), for a total of 10 inches from top of finished floor to bottom of beams/joists, leaving a post height of eight inches…

CUT IT AND FASTEN IT TO THE PIER!!!  AFTER ALL THAT FIGGERIN’ DON’T LET THAT SUCKER ESCAPE!!!

Whew!  Glad I got that out of my system.  Now, where were we?

Oh yeah…post setting…

The hard part is done, assuming you got your pier locations right and got the first post height right.

There are three ways I can think of to figure the height of the other posts.  Two REQUIRE two people, and I recommend it for the other one.  Doing it by yourself falls under the ”don’t try this at home” heading, and since it IS your home you are building…

Method #1 requires a piece of string, a tape measure, and a string level.  By the way, this is the least accurate and most frustrating.  Be sure to take your meds, especially the valium and any heart meds, first.  It’s also the only way I can figure for one person to do it without help.

Nail a strong piece of string (use Mason’s Twine) to the top of your first post, pull the string to the location of your next post, hang the string level on the string while holding the string directly across the pier, move the string up and down until the string level says the string is level…

“…string level says…”?  I didn’t know string levels could talk.  Hmmmm…

…and use the tape measure to measure the distance from the string to the top of the pier.  That is how long that post will be.  Do this for all the posts using the same base post for all of the others.  Moving from post to post as your starting point will result in unlevel, uneven floors.  Off by a half inch per post on my 14 posts would have had me 7 inches out of flat/level.

Method #2 involves a builders level/rod and two people.  Set the level level (sounds weird, but it’s right…you want your LEVEL to be LEVEL), 20 or so feet from the nearest pier, and on high enough ground you won’t have to reset when moving from post to post (same reason as using one base post in method #1).

Note:  This method will work at 2AM, with no moon, the headlights from two vehicles on, and each person holding a Bic lighter.  Don’t ask me how I know this…

This is probably not the right way to do it, but it works for me.  Set the rod on top pf the base post, and see where the crosshairs intersect the rod.  Let’s say 4 feet 8 inches.  You know the first post is eight inches tall, so the crosshairs are four feet above the top of the post.  Now set the rod on an empty pier and see where the crosshairs intersect it.  Subtract the four feet that the level is above the original post top and you have the height of the post you are measuring for.

Method #3 is the same as using a builders level except you use one of those spinny-lasery thingys (highly technical construction term)  and see where the laser light hits the rod for your measurements.  I’ve never used one but I’ve heard you have to be in low light as the laser is hard to see in bright sunshine.  Also they are expensive as all get out, renting or buying.

There!  That’s the ticket out of using a laser…too dang expensive for a one house…er, one yurt…job.

There…continue until you have a post on each pier, then go have yourself a cold one.  Me?  I’m going to bed…it’s 3:45AM.  Next post we’ll talk about beams and joists.

All about Bob the nutjob!

Bob is a N Georgia blogger, homesteader, yurt liver, self-sufficiency nutjob, pig farmer, political activist, politician baiter...and the best damn cook you know that doesn't make a living at it.He can be followed onTwitter. You can also "Like" our Facebook page.

  One Response to “Yurt foundation…pier and post”

Comments (1)
  1. Great blog post.Thanks Again. Want more.

     

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