Pole barn reinforcement

[scrimshaw33]

I'm making a very large pole barn out of hand hewn white oak beams (100 years old from four tobacco barns I salvaged) that are very heavy, probably 700 lbs each or more (?). They are 20 foot long on average. I've already got all the posts set 4 foot in ground with dirt tamped, but after a heavy rain and some wind the poles still are moving laterally even with reinforcement from 2x6 girts. I don't have the roof trusses up yet. One thing I haven't done that I'm going to do is place a cross base at each corner and perhaps place a cross member between each post.

For the post holes I placed a 6 inch pad of concrete slab at base, and again I tamped hole with dirt around post.

My question is, would I rot the post if I dug around each post individually about 2 foot down and placed concrete to reinforce the posts, or is this just not necessary and is the lateral movement normal without the trusses? I would really feel more comfortable with the concrete around the posts but have read differing accounts as to whether it will rot the posts or not.

I've also considered using cables run from the corners inward to meet in the middle of each wall, separately down to a anchor. Any other ideas?

 

[milkman636]

6" sounds a little light on the footing for the size of post you are describing. Local codes required thicker footings under my posts. The girts should keep the side walls from racking, but you'll need diagonal (knee) bracing to keep the posts plumb. During the construction phase,temporary ones are usually nailed to the posts at one end and anchored to the ground at the other prior to the backfill. Once the framing is assembled they can be removed before the siding goes on, assuming the framing is done right.

 

[scrimshaw33]

I do have temporary bracing up and with it, the structure doesn't budge, but still considering whether or not concrete will possibly cause any issues underground rotting post if poured around it, that's my main question.

 

[terry.dinerman]

Scrimshaw-

I built pole barns for a living in another life...

A 6" pad sounds pretty substantial to me....but your codes, if any, may require more...some settlement is going to occur, even in the most substantially consolidated subsoils, so dealing with some amount of settling is going to be part of your future unless you are lucky enough to plant your poles on top of bedrock...an advantage of a soil backfill is: in the future, if the need arrises, you can jack up a low point, dig out a footing and pour additional concrete under the pole as a shim...

Until your building is sheeted, the unconsolidated soil around the poles, even tho thoroughly tamped, will still be soft enough to allow some motion of the poles...expect it...be ready to deal with it by having a couple of good come-alongs and some slings around to straighten things up when you sheet.

Do not put concrete around your poles...you will hold water in contact with the wood, accelerating rot, and you will create a 'stress riser' between the wood and concrete at the top of the concrete column, concentrating the bending forces that wind racking with put on the pole, rather than allowing them to be distributed down the full length of the pole.

Keep your temp bracing in place till you sheet....then get rid of it....you should not need much in the way of permanent diagonal bracing in a fully enclosed structure....straighten your poles as you sheet the structure...pull your temp bracing and even the fasteners out of nearby girts and rafters if you have to allow you to plumb the poles and walls and then re-install the structural members as you go...refasten any re-worked structural members with, and add tek screws to the existing structural members as you go...the screws are far more resistent to withdrawl forces than even the most agressive pole barn nails....then, your siding should be more than enough to provide the lateral support to withstand racking forces...

Cables are not a good idea, even in an open structure that requires serious wind-bracing....I would always use a minimum of 2x6 lumber screwed and thru-bolted to the poles and girders for wind-bracing...the old man who taught me how to build used to say..."If you need bracing, you may as well go BIG..."

Hope this helps...how about some pictures?

BE SAFE OUT THERE....

Terry

 

[Barry 1]

If you set oak posts in the ground,they will rot no matter what you do.

 

[scrimshaw33]

Photo of barn I took this morning:

 

[scrimshaw33]

Thanks Terry, very good information. I've got it stabilized now with support from the outside and inside which you can see from the pics which like you said I'll remove as I need to when adding trusses and finishing outside. I'm glad to know that it should stabilize as I go. The 2x6's are a great idea. I have 20 foot 8 inch cedar poles called tier poles from the tobacco barns and also might use those. They are solid and I have over 50 of them. These of course I'd use for the cross members at the corners.

Is there any reason I should use the cross members along the walls as well in addition to just the corners?

And, any reason to sheet the outside with plywood/OSB first for extra strength vs just sheeting with the metal?

Scrimshaw-

I built pole barns for a living in another life...

A 6" pad sounds pretty substantial to me....but your codes, if any, may require more...some settlement is going to occur, even in the most substantially consolidated subsoils, so dealing with some amount of settling is going to be part of your future unless you are lucky enough to plant your poles on top of bedrock...an advantage of a soil backfill is: in the future, if the need arrises, you can jack up a low point, dig out a footing and pour additional concrete under the pole as a shim...

Until your building is sheeted, the unconsolidated soil around the poles, even tho thoroughly tamped, will still be soft enough to allow some motion of the poles...expect it...be ready to deal with it by having a couple of good come-alongs and some slings around to straighten things up when you sheet.

Do not put concrete around your poles...you will hold water in contact with the wood, accelerating rot, and you will create a 'stress riser' between the wood and concrete at the top of the concrete column, concentrating the bending forces that wind racking with put on the pole, rather than allowing them to be distributed down the full length of the pole.

Keep your temp bracing in place till you sheet....then get rid of it....you should not need much in the way of permanent diagonal bracing in a fully enclosed structure....straighten your poles as you sheet the structure...pull your temp bracing and even the fasteners out of nearby girts and rafters if you have to allow you to plumb the poles and walls and then re-install the structural members as you go...refasten any re-worked structural members with, and add tek screws to the existing structural members as you go...the screws are far more resistent to withdrawl forces than even the most agressive pole barn nails....then, your siding should be more than enough to provide the lateral support to withstand racking forces...

Cables are not a good idea, even in an open structure that requires serious wind-bracing....I would always use a minimum of 2x6 lumber screwed and thru-bolted to the poles and girders for wind-bracing...the old man who taught me how to build used to say..."If you need bracing, you may as well go BIG..."

Hope this helps...how about some pictures?

BE SAFE OUT THERE....

Terry

 

[scrimshaw33]

I sure hope not Barry. Maybe you're right though. I researched all I could and talked to many local farmers and they said white oak was rot resistant. I know the beams are white oak as they all had some bark left on them, which I stripped off before setting. I also researched online and most pole barns and timber frame barns that are old were made out of white oak due to its rot and insect resistance. Even ships were made from white oak. These beams are also 100 years old so they are dry as heck...not to mention they've been dried from tobacco smoke from years of use.

But please correct me if I'm wrong, at least I know what I'm getting into if I am. That was a concern initially but then the more I researched I thought I was OK. I also planned on using something like Timbor and other wood preservative products by drilling holes at the base, when I'm done and inserting the chemicals to ward off rot. Currently all the beams are solid through and through.

I do know red oak is not rot resistant but again white oak is supposed to be. Also the wood is all heart wood as opposed to a newly cut white oak where the sap wood is still intact.

If you set oak posts in the ground,they will rot no matter what you do.

 

[Barry 1]

White oak is real good for siding,but it rots in the ground.Every old tobacco barn I've seen,slowly sinks into the ground.It might last for 20 years??? at least pour some insect killer around each post. My barn was white oak,and I had to jack up the posts,pour a pad,and scab together the end with treated wood,before I set them on concrete. The outer posts were the worst,but even the center(real dry) ones were rotten and eaten up with grubbs and termites.

 

[scrimshaw33]

Bummer...did you use anything like Timbor or Boric acid to prevent rot Barry? The tobacco barn beams were placed horizontal on rock foundation...I believe they are built a lot different here than in KY. The tobacco barns there are built looking like barns from what I've seen where ours in NC are almost like cabins. Anyway, doesn't matter here in this situation other than that my logs don't have rot in them (now).

I guess you're saying that worst case if I notice rot in 10 years or more, I can put foundation under them and cut off the rotted part?

White oak is real good for siding,but it rots in the ground.Every old tobacco barn I've seen,slowly sinks into the ground.It might last for 20 years??? at least pour some insect killer around each post. My barn was white oak,and I had to jack up the posts,pour a pad,and scab together the end with treated wood,before I set them on concrete. The outer posts were the worst,but even the center(real dry) ones were rotten and eaten up with grubbs and termites.