On 13 Apr 2004 08:39:57 -0700, (Don) wrote:
I am wanting to build an extra garage because mine is full. I am
thinking of building a pole barn type with 2 garage doors. Probably
30x30.

I own a couple of much larger pole barns, dirt floors, but when it
came time to build my 30x34 two story shop, I opted to use post
and beam construction on a foundation and slab floor instead.

Depending on climate, soil type, and the EPA, pole barns have a
number of unfortunate issues having to do with setting the poles
directly in the soil. If your climate has frost heave issues, the walls
will quickly become wavy as the poles heave differently. The poles
may deteriorate fairly quickly too, depending on soil chemistry and
your ability to get properly treated poles (the EPA now requires
creosote treated poles to be handled from cradle to grave as toxic
waste).

Replacing a bad pole can be a *real* problem. Usually it isn't
practical to remove the bad pole, you have to sister another
pole in next to it. But when you do that, nothing fits, so you have
to patch the girths and trusses too. A real nightmare. You can't
really seal a pole barn either.

Post and beam in a shop size building is about as conservative of
materials (ie low cost) as pole barn construction, yet it avoids most
of the problems of the pole barn. The wooden posts (6x6) are set
on 8 foot centers on a floor plate (2x6) bolted to the concrete.
Nothing wooden touches the soil or is exposed to the elements.
The outer sheeting, and the foundation, totally seal the building.

Three rows of girthing (2x6) are run, bottom, middle, and top around
the outside of the posts (same as a pole barn). The "tin" screws to
these (I actually used high strength baked on enamel finished sheet
steel guaranteed not to fade or rust for 20 years, but people in the
trade still call it "tin"). Use of screws, not nails, with rubber washers
under the heads is a must. These won't loosen, and they won't leak.

On the interior side of the posts, 2x6 girths are run at top and bottom.
These, with their matching girth on the outside, form the load beams
for the structure, and also provide a place to attach any interior panels.
If you want a really rigid structure, add 2x4 crossbucks between each
pair of posts (cut to fit interior so they don't interfere with the girths).

The beauty of this style of construction is that you can lift and handle
all the pieces by yourself (though a helper makes installing the girths
a lot easier). No problems with frost heaves. No wood is exposed to
the elements. The building can be really sealed (helps keep dust down,
and is a must if you want to heat or air condition the space). And if you
do ever need to replace a post or beam, you can do it a *lot* easier
than replacing a pole in a pole barn.

I have been fighting with the idea of building it myself. I have a
tractor with a bucket available to me as well as an auger for the
tractor.

Standing the poles up in the holes is the hardest, and most dangerous,
part of this operation. A 2 ton truck with a hydraulic lift grain bed makes
it possible, a crane truck makes it safe. I've done it both ways. To make
the poles last longer, put a few inches of fist sized gravel in the bottom
of the holes, and fill the holes with concrete to cement the poles in.
Mound the concrete up above ground level so water can't stand against
the wood.

The best place to get poles is from the power company. They're always
replacing broken poles, and the salvage is often long enough for your
purposes. They're glad to get rid of the broken poles, because of the
cradle to grave EPA thing (ie you're saving them having to pay to have
a toxic waste disposal facility deal with them). You'll have to sign a
paper assuming ultimate disposal responsibility for the poles, and that
can put you on the EPA's radar. I prefer to avoid that, but the price is
right for the poles.

Any advice? How far are posts, trusses spaced? How do I ensure the
building is square?

8 foot centers is pretty standard for the poles. Note that you'll be
attempting to fasten flat girth boards to a round pole. That doesn't
work very well if you just nail or screw them on. You want to either,
1) chainsaw flats on the poles, or 2) use through bolts, or both.
Roof trusses can be done a couple of ways. The usual way is to
bolt them to each pole, so they're also on 8 foot centers. Batten
boards then are run crosswise every 24 inches. The roofing tin
fastens to these. Alternatively, you can sheath in plywood and
tar paper, then put on shingles.

To determine if your walls are square, measure from the top of
one end to the bottom of the other. Then measure for the bottom
of the first end to the top of the other. The two measurements have
to be the same, or your wall is racked. You can measure across
opposing walls on both diagonals to see if the overall building is
square. Obviously, do these latter measurements before you dig
the holes for the poles, then again after they're up, but not yet
cemented in, so you'll have a chance to correct any errors.

Frankly, for a modest sized building, post and beam if far superior
to pole barn style construction. I'd strongly urge you to consider
that, particularly if you're going to put in a concrete floor anyway.
Just dig down around the perimeter to form an enbloc foundation
before you pour the slab. (Depth of the foundation depends on
climate, here it is 18 inches for a single story structure, 24 inches
for a 2 story structure. In colder climates it'll be deeper.)

I also dug cross trenches to form concrete beams under the floor.
This allowed me to pour the slab as one piece with no expansion
joints. I used rebar and wire reinforcing, of course, and a 6 inch
slab depth over a 10 inch compacted gravel base. That, with the
added enbloc beams, gives an incredibly strong structure that
won't crack under the influence of frost heaves (or pretty darn
heavy machinery loads either).

The dirt work and slab are the most expensive part of the project.
Some people might say I went overkill there, but it is the base on
which everything else depends. I acted as general contractor, but
I subbed out the dirt and slab work, as well as the framing and tin
work (under my close supervision, since none of the subs around
here had ever built a building quite like this one).

Total cost, including wiring, plumbing, and HVAC (did all of that
myself except trenching in the underground service feed, which
the power company did), came in under $13,000 for 1800 square
feet of heated and air conditioned work space.

The second story only added about $3,000 to the construction
cost, a fair chunk of that went for a 24 inch composite beam so
I wouldn't have any posts out in the middle of the first floor. Think
about that if you want to cheaply double your floor space.

Note, that price is 10 years old, and I'm a pretty good scrounger
and negotiator, but labor costs are fairly high in this area, so I
suspect you can comfortably come in under that figure for a very
solid single story garage. The building is still tight, no cracks in
the floor, so I think I did good.

Oh, BTW, 2 10 foot high by 14 foot wide steel garage doors are
on one end, a people door on one side, and 2 high mounted
(so people can't see in easily) windows in the back, and 2 upstairs,
one at each end (should have put in more windows).

I also should have put in an outside door and hoist beam for the
second story. As it is now, anything going upstairs, or coming
downstairs, has to go by way of the internal stairway (two flights,
folded in a corner to take up the minimum amount of space).
Not a good plan for heavy or bulky items. I may still add this.

Gary