14 x 20 Pole Barn using 4x4 posts

Dougryan · Jun 7, 2017

Hi,
I've built a few sheds over the years using stick built methods with framed wooden floors. A couple of 12x16, and one 12x12 on a cement slab, so I'm familiar with 2x4 based shed building.

Now I'm looking to build something a bit bigger... 14 x 20... and really interested in a small pole barn style structure.

My first major question, since I'm not familiar with this building style, is about the poles. I would prefer to use 4x4s since they are easier to work with. I'll need 12 footers so that I can bury 4' and have 8' walls. A 12 foot 4x6 or 6x6 would be really heavy and hard to plumb etc. While I could use larger lumber and 10 foot spacing, I was thinking that I could use 4x4 posts and 5 foot spacing.

So five 4x4 posts along each 20 foot wall, plus two more posts along the 14 foot walls. Evenly spaced on one wall, but a bit wider on the other to allow for a 6 foot wide door.

What do you think? Some folks really frown upon 4x4 posts even in the smallest pole barns. Some promote 6x6 or even 8x8 posts.
I should also mention that I plan to use 2x4 girts and T1-11 siding. So the siding itself will add to the rigidity and support of the walls.

Thanks,
Doug

newbury · Jun 7, 2017

Several things immediately come to mind:

What is the source/quality of your 4x4's? I've seen a lot of HD, lowes, and similar twist horribly as they age.
Another option would be using 3 2x4's sandwiched together such that the "grain" tends to go opposite, still the weight of a 2x6 but if done right should hold together well.

Why T1-11? Do you like to paint and replace? I built a 10x15 shed back about 1985 in Virginia. Used T1-11, primed and painted (and painted, and painted, about every 3 years). After about 8 or 10 years the bottom edges were starting to delaminate.

Tore off the T1-11, put on 4x8 sheets of Hardieboard. Painted once.
Still looks like the day I put it up.

Another good choice for siding would be metal.

Dougryan · Jun 7, 2017

4x4s would be from my local HD. I could see using three 2x4s together. A bit heavier than a 4x4 but stronger than a single 4x6. Something to think about.

T1-11 is just popular around here. I did a quick search for the HardiePanel (4x8 siding) and it's just not available around here (western NY). The only way I could find it is: Get an In Home quote from HD and it requires HD Installation. That's crazy. I did use HardieBacker board for a recent fireplace project and I really liked working with it. I can see the benefit of using cement board as siding. I'll keep my eyes open and see if I can find it from other sources.

KennyG · Jun 7, 2017

From a strength standpoint, the 4x4s are probably ok, even with 8 foot spacing for a 14 foot span if you are using a metal roof. However, I would recommend going to 4 x 6 because of the lumber quality. Around here, it would take some sorting to find 4 x 4s that are straight and clear enough to make me comfortable. I also wouldn't go with the T-11. You will need girts anyway to span the poles and metal is much more durable. If you need T-11 to match other buildings, I would say forget the poles and go with stud walls.

dmccarty · Jun 7, 2017

To add to what Newbury said, I would also be concerned with a five foot spacing of 4x4 posts where I live but if there was any chance of a decent snow low... I can't remember the load numbers for a 4x4 but they would on the Internet somewhere along with the roof load requirements for your area.

I was looking at a Morton built barn years ago and I was impressed with the 2x6 boards laminated together to form 6x6 posts. The posts were strait and with a 2" thickness the wood treatment really should get to the inner part of the lumber.

When I have bought treated lumber for projects that need to be done right, I go to a somewhat local wood treatment plant that has been in business for generations.

Using 4x4s makes me nervous but running the numbers should make things clearer.

Later,
Dan

wawajake · Jun 7, 2017

In my younger years , I installed a few clothesline poles using 4 x 4 pressure treated posts , for myself and friends........big mistake, they all warped over time . Unless you have a very good source of wood , I suspect yours will be the same result. Laminating a few 2 x4 or 2 x6 together would help alleviate the warp potential.

CalG · Jun 7, 2017

I've built a car park just a bit larger. It's a salt box metal roof with open gables and no walls. It's just standing on 7 4X4 posts. I did "double up" on the bottom 8 feet with a sandwich of the 4X4 between a pair of 2X6 pt.

The location is in the woods, so wind loads are tempered. We get the snow however. That seems to slide nicely but it sometimes takes a day of warmer weather.

The car park is 5 years old, and still standing. I do have a little trouble with one corner where I could not get down into the earth as deeply as I would like. Ledge is like that. ;-) Frost lifts the post some springs. I need to dig it out to gravel and sleeve that post. Not a big issue, the structure is pretty flexible, I call it "earthquake proof". ;-)

Deere Dude · Jun 7, 2017

If you are ever going to cement the floor I would cement it now and just put 2x4 walls up and forget the pole barn structure style.

Dougryan · Jun 7, 2017

Well, my first intention was to do a cement slab and stick frame it. Then I thought about the need for a monolithic slab.

I didn't do this kind of slab for my 12x12 shed since it was so small. But I figured the 14x20 would need some type of reinforced footings etc.
That got me thinking about the pole barn idea. Let the poles do the support work and at a later time, pour a 4" slab inside. I really don't want to do a wooden floor again. It will be either cement on day 1 or gravel followed by cement in the future.

So, I guess I'm still up in the air about stick vs pole. By the time I do laminated posts (2x4s plus glue and bolts) or larger 4x6 or 6x6 posts, the cost appeal of the pole barn becomes less of an issue. Plus, I can sling 2x4s around by myself all day. I could manage 12 foot 4x4s too... but when we start talking about larger dimension posts, it's no longer a solo project.

Back to the drawing board...