Pole Barn Question

[mytoys]

I have a question for those of you that have experience with pole barns. I see a pole barn in my future so I'm starting to think about it. I don't have a post hole digger but I have a backhoe. A post hole digger doesn't always work so well on my property because of all the rocks. Anyway, I know it's not ideal but, can I dig the holes for the posts with my backhoe? I realise I'm disturbing a lot of earth. I appreciate your thoughts.

Thanks.

 

[cowboydoc]

You can but that's alot of backfill. It's also difficult to get them tamped back so there's no wobble with that much dirt. If nothing else have somebody come dig them with a 12" auger or a hardened bit auger. That's an awful big hole to dig down 4' with a backhoe.

 

[kemartin3]

Maybe you have a reason to only be considering a pole style barn. If I had a BH, I think I'd pour a footing and stick frame it.

Kevin

 

[NIXON]

I'm with Kevin on this . If you're going to use a BH , I'd Dig footings and pour a slab . John

 

[Henro]

I guess it depends if you can get the concrete there easily for the footer...if you can then the slab naturally follows... /forums/images/graemlins/smile.gif

I guess I could have [not real easily, but not impossible either] but I decided to do a pole style construction of my shed. I do think the post hole digger was great though...if I had HAD to did the post holes with my backhoe...I guess I probably would have followed the advice above and went the footer/block wall route...

 

[wroughtn_harv]

I don't see where digging your holes with a backhoe would be a problem. It is one situation where a twelve inch bucket would be ideal.

I would suggest digging a trench if the rock will allow you to do that. I know, sometimes digging in rock you end up with a hole that's real big at the top.

Let's say you set the hoe in the middle and dig your holes so the open or sloped side is towards your inside. Once all your holes are dug to depth you have two sides vertical and parallel and one that is slightly sloped while the other is very sloped.

You then put in a sonotube. That's the cardboard concrete form for piers. You can get them in various sizes at good building supply stores. Take care to keep them in line, stakes and two by forms on the surface work fine, and then back fill around the sonotube.

You now have your post hole.

If you have cleaned the hole to natural earth at the bottom and you're kept the slope to a minimum on two sides and back filled carefully you should have this puppy by both ears.

 

[Junkman]

That is what I did a couple of years ago and the very first winter, the tubes were pushed out of level by the frost. I hadn't built on them at that point and it is a good thing. I would have had one lopsided deck had I not waited.

 

[yooperdave]

I just had a pole barn built.

The auger that the contractor used bent on one of my rocks, so I had to contract someone to dig 23 holes with his back hoe.

It turned out just fine.

The key is to bear the foundation on either undisturbed soil, or compacted soil.

Good luck.

Yooper Dave

 

[dmccarty]

mytoys,

I have the same situation as you do.

I really don't like the idea of putting the poles in the ground
even with PT wood. So I'm just going to put in concrete piers,
put in Simpson Strongtie post bases and put up 6x6 12' PT
posts.

This way the wood is out of the ground. I have concrete below
grade. And the work fits my equipment. Buried poles would be
stronger from a wind load perspective but I'm no really worried
about that issue.

To start I'll put down an ABC and when we have money go back
and pour a concrete pad. We just don't have the dollars to put
in concrete right now. I thought about putting in a concrete
foundation and pad to start but it does not fit the budget.

Later,
Dan

 

[5string]

Obviously, you do not plan on getting a permit for your future building - that's O.K. by me, like everyone else, I get frustrated with the beaucracy associated with that path. However, if for grins you decided to run your project past a engineer it wouldn't take long beacuse your building would have no calculable shear capability. Simpson straps are for vertical "up" loads, not shear. If I came by for a visit and the tree tops were moving I would not be in your building. The loads generated on a large flat surface by even small wind gusts are impressive.

I do have a suggestion that you may want to consider. When you poor your slab, sink J bolts in between the posts. Then, frame-up 2 X 6 walls and stand them in between the posts. Double-up the 2 X 6's common to each post and lag them in. Also, you will need to let-in a angled support member or have lots of blocking. Please note that you would still probably not meet standard shear requirements. You will also gain the ability of being able to insulate if you choose.

I am in the middle of a pole building project. I asked for commercial girts so I would have a 5.5 inch space between the outside siding and drywall for standard house type insulation.

 

[dmccarty]

5string,

I never said I would not get a permit. I might be able to build
without the permit but its a big might. Even if I could build
without the permit I would prefer to have one so they can tell
me of any problems they might see.

To start with the barn will not have walls so wind pressure on
is not really an issue but up lift could be. The post caps I am
looking at using have some pretty hefty uplisf numbers and
requirements for installation. They are buried into the concrete
pier when it is poured. The 6x6 is connected to the post base
with something like 12 16D nails.

Currently I have only run the structural numbers on how much
load the posts are going to have to hold up. All of the numbers
I have calculated say I'm WAY over built on what I have
designed so far. And I made assumptions of a 30% increase in
snow load for my area. The table I used to calculate the dead
load for snow was based on a 50 year weather event. I
increased the load by 30% just for grins and giggles and only
ONE post in the center of the barn is close to its load limit. The "book" says I'm wasting money on some of my posts since they
dont have enough load and I can decrease the column size.
I'll spend the extra few bucks on 6x6s.

Wind resistence is next. My neighbor has a similar barn built on
concrete piers and its survived all of the huricanes we have
been cursed with over the last few years. Heck, for that
matter so have the barns in my family that are really close to
the coast. Those barns are built on rock and maybe brick piers.
They have only be standing for 50 years or so. Termites and
wood rot is killing them.

Later,
Dan

 

[Junkman]

I used the metal brackets when I built my deck on concrete piers also. I used a hammer drill to go into the concrete and then I uses a fast setting epoxy cement to put in the threaded rod that holds the brackets. I know that the bolts are not going to pull out...... I put a 3/4" breaker bar on them and couldn't pull them out the next day...... wonderful stuff that they make now for securing things...

 

[dmccarty]

Junkman,

That is VERY good info about the hammer drill and bolts.

One of the problems in doing things with the piers is getting
them plumb and level. I THINK I have figured out how to do this
cheap and easily. But if I drilled and then expoxied the bolt into
the pier it gives me more wiggle room if I mess up the pier
placement....

I went through the wind resistence calculation last night. Still
have a few more passes but it looks like the post bases can
more than handle the load. One of my "picks" for a base cap
uses two bolts and the cap looks like it has some wiggle room
on placement. The strongest base cap has to be imbedded in
the wet concrete but it sure would tie down the 6x6.

What kind of hammer drill did you use? Was it cordless? Is this
a good excuse to get a new toy, errr, tool?

Later,
Dan McCarty

 

[mytoys]

All,

Thanks so much for your insights and experience, this gives me a lot to think about.

Some of you have mentioned using the backhoe and pouring a footer, and wall system. I've been tossing around this idea as well. In my area you've got to dig to 4' to for the footing. Not a problem but will definately be more expensive than a pole barn (as far as i can tell, please correct me if you feel otherwise).

One of the benefits of traditonal framing is that, if i plan to insulate and heat part of the building, which i will likely do in the future, then the framing is already in place to do so.

Anyway, I want your opinions. I'm trying to save money by going the pole barn route but given that I intend to isulate and have a cement floor some day, should I reconsider? Should I just stick with traditional framing with a foundation system? What are the pros and cons of each? How can i save money and get what I need?

Again, thanks so much for your thoughts and opinions.

 

[5string]

Well, there I go making assumptions again (no permits, walls, etc.). My wife says I need to quit doing that. I had a professor that insisted that anything with less than 4 walls be clearly identified as a structure, not a building, barn, etc. I suppose it is kind of like any flying machine that has fixed wings is a airplane and anything else is a aircraft. So, at the risk of again being presumptuous I will assume that you are not interested in insulating your structure since you have no walls /forums/images/graemlins/wink.gif.

Yeah, since you have no walls, standard tables are not applicable (actually they are, but let's not go there). However, I would not discount the shear component. If I remember correctly, structures use uneven snow loads to evaluate shear. Also, a roof with no walls is basically a airfoil. Depending on the pitch of your roof, a significant low pressure could develop on the top (relative to the bottom) which will make it want to "fly". Since this lifting force will be non-uniform (tension and compression) lateral loads will be experienced. I have already said more then I intended - have fun with your new structure.

 

[Junkman]

I purchased a 1 1/2" Milwaukee hammer drill that was used and bought new drills on e Bay for little money compared to what they cost in Grainger catalog. I drilled 3/4" hole and inserted a 1/2" piece of threaded rod in them after the hole was filled with the special cement. This is the same product that they set the table stands into in the McDonald's restaurants. Once it sets up, it will not pull out no matter what you use to pull on it. I think that the entire concrete pier will move first or the threaded rod will break. It takes about 30 minutes to cure enough to bolt down the brackets and about 24 hours to totally cure.
Personally, I would rather see a stick built building on a foundation wall system as opposed to a pole barn if you are thinking of heating it.... Just my opinion..... if you decide to pour the footing and foundation yourself, don't forget to put a "key" into the footing. This is done by placing a 2 X 4 into the center of the wet concrete parallel to the footing. After the footing dries, you remove it and it leaves a depression that when you pour the walls, will keep the walls keyed to the footing and they can't move off the footing. If you are in a wet area, put 6" PVC pipes through the footing on each side. These are so when you are finished with the walls you can put a drain both inside and outside the walls to eliminate water from building up under the building. Use 4" perforated PVC pipe and 3/4" crushed rock for drainage and pipe away from the building to a low spot.

If you decide to use the concrete pier method, consider the plastic forms that the tube fits into that makes a "foot" at the bottom. It will go a long way to adding stability. As I had said in the past, if you dig them with a backhoe, you run the risk that they will move in the future while the ground settles.

 

[dmccarty]

mytoys,

The pool barn is cheaper than a slab. I just ran the numbers to
pour concrete for my barn. It would cost 2,000 dollars just in
concrete. That did not include digging, forms, or gravel/sand/ABC.
Concrete in my area is $90-100 per yard.

I don't have a complete cost on my barn but if I just build the
barn, no siding, its going to be near $2,000 - $3,000.

There is no reason that you can't heat a pole barn. Go get this
book....

"Practical Pole Building Construction: With Plans for Barns,
Cabins, and Outbuildings" by Seddon and Williamson.

Its very good. It will answer many of your questions. So far
though I have not found any info on building with piers...

One of the advantages with a pole building is that the poles hold
up the structure. This means that you can build the supports
and roof first. Then, as in my case, when I have the dollars I
can go back and build the walls and floor for my workshop. You
can frame it conventionally or with slightly different methods
that are shown in the book. But both ways allow you to build
over time and if you want the building insulated it can be done.

Later,
Dan

 

[dmccarty]

5string,

Eventually a section of the barn will be built with a raise floor,
basically a crawl space, and there will be walls on roughly a third
of the building. That might get insulated. It might not. There
are a couple of ways to do the framing and I'll make sure that I
do the framing so that I can insulate.

Yep, roofs do act as an air foil. If I'm reading and understanding
my building/design books I should be ok. The load calculations
take into account the roof size for the wind pressure. I can't
find a chart with mph=psf but my books have some articles.
One of which is that 80 mph wind is 15 psf. Another one
mentions that coast MA has a requirement for 21 psf. So I used
21 psf that should be good enough.

My roof is going to be cheap. 26 inch fiberglass panels that
have a 20 year warrenty. Whatever that is worth. I'm really
wondering if they would not pull off in high winds...... 8-(

Later,
Dan

 

[dmccarty]

Junkman,

Thanks for the info on the drill and epoxy.

I can insulate the building if we need it. One part of the barn
will be inclosed at some point and that might get insulated. Its
a long story about this barn and how it changes size over time
but it looks like we are just going to build the structure and
roof first. Then when I have time and money the barn will get
fleshed out.

I'm pretty certain that I will use the premade concrete forms.
This is an open issue until I make sure that the building can
handle the wind shear. One way to handle the wind is to have
a double layer of plywood over the surface of the building. It
looks like I would only need two feet of wall space around the
poles to do this. There are techniques called moment walls,
I hope I got that right, that are very applicable to pole buildings.
Basically you make sure that the post and beams are very ridgid.
If they are ridgid they can't rack under a wind load. And if they
can't rack the big bad wolf can't huff and puff to blow my barn
down. It looks like, still have to dig some more, that using
some of Simpson's post caps provide moment walls.

Back to those piers. The concrete forms in the big box store
is a four foot tube. Not footer. So I was figuring I would have
to build a footer, cut the tube in half, and then pour the pier.
Our frost line is only 6 inches. But if I do what I just said I
would have a pier foot three feet below grade. The tube with
the elephant foot would be easier....

When you mentioned that the pier may move when the ground
settlles. In which way do you think the pier may move? Down
or side to side. I'm thinking side to side....

I suppose I could fill in with ABC around the pier. That should
lock it into place.....

Thanks for the info and thoughts,
Dan

 

[cowboydoc]

You'll be fine with the air foil theory Dan. We've got several hay barns built with no sides and just a roof. Nothing fancy on the construction. Just poles 4' in the ground. Trusses 8' apart and normal purlin framing. We've had 80 - 100 mph winds and never had one blow over. Where this comes into play is when you have one side open and the wind can't blow through. With the sides opened up it won't be a problem.