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Considerations for sealing wood beams for ground contact

Considerations for sealing wood beams for ground contact

Considerations for sealing wood beams for ground contact

(OP)
I am trying to come with a solution to seal engineered poles or beams for long term ground contact. Actually will be concreted in place but the general understanding with wood rot is the combination of O2 and water is what causes rot. Either is missing and rot does not occur?

I have seen everything from tar, to plastic bags, to injections to protect the wood. I am considering a bit more invasive operation of fiberglassing the outside of the beams. I know fiberglass would have the durability and longevity for this application but I do have concern of locking in any moisture and thoughts of any dimensional changes of the lumber causing issues?

I have also thought of some type of molten plastic dip as well. I just don't think people take this issue seriously enough as it seems to be the prime issue regarding these types of structures.

RE: Considerations for sealing wood beams for ground contact

Impregnating with creosote is the typical solution - used for railroad ties and telephone poles.

Simple barrier materials will be breached and then retain moisture. Use good drainage if possible.

Check the US Forest Product Laboratory for information; they support "Durability and Wood Protection Research"

RE: Considerations for sealing wood beams for ground contact

(OP)
I hear you on barrier failures. If I apply glass, there is really no way to practically test for leakage before installation.

I do not believe Creosote is available for all parties? IE highly toxic and likely to leach, possibly into water? I guess I am trying to use something that is safe but I assume safe also means safe for critters too... I have no remorse for wood eating critters.....Terminites be my biggest frustration.

I know Borates are common treatments but I want a 100yr plan in place whether that is with injection tubing by the wood or what not.

RE: Considerations for sealing wood beams for ground contact

What's the exact application? Could you substitute concrete or a polymer material? How about using redwood?

RE: Considerations for sealing wood beams for ground contact

(OP)
This is basically a pole barn. Need to have the beams secured into the ground for structure so pouring a footing or pier loses the continuity in lumber grain. However, I was sort of thinking of something synthetic and tying it together above ground but I remember all the synthetic lumber products having very poor structural specs.


I guess I am open to ideas. Still trying to toss the idea of concrete around all the poles. great for firm connection and stiffness but possibly will retain water?

All in all, every effort will be made to drain water away from these areas which I think is a prime reason of failure in most of these types.

RE: Considerations for sealing wood beams for ground contact

What about concrete poles?

Mike Halloran
Pembroke Pines, FL, USA

RE: Considerations for sealing wood beams for ground contact

(OP)
Not even remotely familiar with something like that. I have to consider attaching a lot of lumber to them though which could present challenges.

Are you thinking of pour in place or precast?

RE: Considerations for sealing wood beams for ground contact

I am presuming you have looked at preservatives like: chromated copper arsenate (CCA). Wood treated with CCA is one of the most common types of preservative-treated lumber available today. It is toxic to termites and to fungi that like to eat wood.
If you have livestock that like to chew on wood, a common method of preventing contact is a sheet metal collar around the treated base.
Also, if this is inside, the barn, your floor should be dry, unless you have run through from a higher elevation.
B.E.

You are judged not by what you know, but by what you can do.

RE: Considerations for sealing wood beams for ground contact

(OP)
Yes, I don't think there is much question that CCA will work "for a while" and probably quite long for termite protection deep inside. However, the surface will lose concentration and rot will eventually set in if they get wet a lot. I am trying to figure out a way to ensure 100yr performance here.

Regarding concrete poles, I would be looking for dimensional products so lumber can attach easily. I do like the idea. many have said just to build an Ibeam building but the interior build out is much more difficult and alterations later are a problem. Already had issues with tension cables in the way. Wood is just more modular. Just need to ensure my connection to the ground is well designed.

RE: Considerations for sealing wood beams for ground contact

A search on [precast concrete poles] found a lot of lighting and utility pole manufacturers, and these guys:

http://www.midwestpermacolumn.com/about.html

Mike Halloran
Pembroke Pines, FL, USA

RE: Considerations for sealing wood beams for ground contact

You want to ensure 100yr performance of a wood product with an air-moisture interface in soil or concrete? Keep dreamin'.

Utility poles, even the ones preserved with creosote, had a maximum life of less than 50 years on average. Many were replaced in the 20 to 30 year range. Those were well treated, partly because of the critical nature of their service.

A barrier system won't work as others have noted. For design, consider pole embedment and forget the concrete. If you want a concrete slab, isolate the slab from the poles with a coating of asphalt mastic.

RE: Considerations for sealing wood beams for ground contact

I remember touring some medieval castle in Germany.

They said the wooden columns were soaked in ox blood.

RE: Considerations for sealing wood beams for ground contact

For what it is worth , I was born and raised in a 400 year old wood framed house, with brick panels or wattle and daub fill ins between the framing. The old builders in that house did not allow the timbers to go below grade. They all rested on clay tiles at ground level.
The timbers were mostly oak, the main frames were about 12 to 14 inches square.
In the 19 60s we discovered that the house had suffered a major beetle attack and had to treat the whole house with Cuprinol wood preservative.
B.E.

You are judged not by what you know, but by what you can do.

RE: Considerations for sealing wood beams for ground contact

(OP)
IT sure looks like Mike and Berkshire have the right idea by avoiding wood/soil contact for obvious reasons. Mike, I really appreciate the link on the concrete columns. I will admit that I am a bit nervous with that system being as stiff and strong as continuous lumber but it fixes two issues I have concerns with. One is the rot, the other is replacement in the event of disaster (tornado alley here).

My brother had done extensive work with polymer modified concrete which might really come in handy here. I was thinking of a custom formed in-ground pier with a dimensional top to attach a custom steel beam mount similar to what was linked. However, it would seem mounting at low as feasible and maybe making the dimensional part a bit wider would better ensure there are no failures there.

Do you guys have any expanded thoughts or ideas on this method of build? I will have to look closer at loads to see how much bending is really on that beam. I seem to remember that uplift is a primary concern but can be easily mitigated with uplift lugs of about any type.

Ron, I did not understand what you meant with "pole embedment but forget the concrete". It sure seems concrete would be the only answer in the ground for lifetime performance? Or stone I guess.

All in all, I would need to devise a slick build style that would be both fast and economical. I have a full machine shop so planned to make the steel connections and such.

Thanks again guys!!! Always get some great ideas here.

RE: Considerations for sealing wood beams for ground contact

Fast line...you don't necessarily need concrete. You can achieve lateral fixity of the poles by appropriate embedment. Many pole barns have no floor other than bare ground. The poles are not usually encased in concrete, just embedded sufficiently to resist lateral loading.

RE: Considerations for sealing wood beams for ground contact

(OP)
Ron, I do agree and have had conflicting thoughts regarding concreting any beams in the ground. Natural contraction of the lumber could cause them to be loose. I had originally intended to concrete and reenforce a floor for each pole, then bed embed with a mixture of gravel and sand for high compaction upon placement. This would also work to drain water but would also easily act as a well for water too.

What are you thinking for a long life pole system? I really like the idea of concrete but setting the lumber in top would seem to build some really high concentrations right at the connection.

RE: Considerations for sealing wood beams for ground contact

Interesting question. I built a pole barn about 17 years ago - 36' X 48', 2 story. I set pressure treated poles directly into the soil about 3 feet deep with a bag of dry concrete mix poured around each before back filling. We get great lakes winters of many freeze/thaws. The soil is mostly heavy clay. So far the poles have held up and the barn is as square and plumb as the day I finished it. But I'm now thinking in the next year or 2 to dig around each and pour a concrete footer for each to give it another 50 + years. Also, the floor is about 6 inches of gravel but I may have a concrete slab poured. It used to house horses and other animals but has been empty for awhile other than some equipment. In retrospect I would have done the concrete at the initial build and set the poles on the concrete.

Have Fun!

James A. Pike
www.xl4sim.com
www.erieztechnologies.com

RE: Considerations for sealing wood beams for ground contact

"Natural contraction of the lumber could cause them to be loose."

Any embedded posts or 2X lumber I've been around have been TIGHT. A few times folks greased up some slightly tapered 2X for removeable formwork and they could not even be chiseled out. Maybe after 15 or 20 years its a different story.

RE: Considerations for sealing wood beams for ground contact

"Natural contraction of the lumber could cause them to be loose."

Any embedded posts or 2X lumber I've been around have been TIGHT. A few times folks greased up some slightly tapered 2X for removeable formwork and they could not even be chiseled out. Maybe after 15 or 20 years its a different story.

RE: Considerations for sealing wood beams for ground contact

My father in law used a copious amount of used motor oil on the sill plate of his garage. This garage is over 60 years of age and to date there were no signs of infestation eventhough abutting the garage was a vegetable garden.

RE: Considerations for sealing wood beams for ground contact

Google Timbersil. Sodium silicate impregnation under pressure for a fairly long time period (days I think), followed by a heat treatment; it was studied/developed at U of Wash. IIRC. Stuff is guaranteed for 40 years, longer than some (most?) plastic/composite decking.

RE: Considerations for sealing wood beams for ground contact

(OP)
Some type of concrete in the ground sure makes more sense so I would never have to worry about lumber in the ground. BUT, this just adds a LOT more complexity in the design and then I need to design and fab specialty splice plates to join to wood above ground. Still just not sure if it is worth all that.

However, I still have to design for tornado failures and rebuilding. The first thought that came to my mind in a pole system is, "when the poles snap off flush with the slab, how do you fix that?" My design originally was to sister additional lumber on each side of the poles up a few ft from the ground to promote failure above ground.

RE: Considerations for sealing wood beams for ground contact

Do not put the posts into the ground but support them on concrete pillars poured into one of the proprietary cardboard tubes like "Sonotube" obtainable from Lowes or Home Depot. Put a 15 inch length of rebar in the top of each post with 8 inches into the post, trowel a slight radius to help shed water, use pressure treated lumber and the barn will last several hundred years. Lay out the location with a transit and string and hire a back hoe with a rotary drill attachment to drill the holes.

Note that your local building code will probably require that either the bare posts or the concrete columns will have to go down four feet to keep them from frost heaving. Mine are only six years old but I suspect my great grand children will have to auction the barn off.

Bob Price



Bob Price
A*G*M

RE: Considerations for sealing wood beams for ground contact

(OP)
Thanks Bob. How do you accommodate the bending loads on the vertical column with only a piece of rebar stuck in the bottom of the wood? I was thinking up something nearly exactly the same as what you propose but with a much more radical connection and a small concrete "post" formed up to get into the dry building space before connecting to wood.

A member above shared a link to concrete posts which gave me some ideas. However, I think the concrete blend will have to be polymerized, possibly add glass, and a good rebar structure just to ensure that area could never fail before the wood poles.

I am also considering that this is getting into a rather complete build design....Pole barns are supposed to be SIMPLE! lol

RE: Considerations for sealing wood beams for ground contact

A wood beam to a concrete pad would still need to be a bolted connection, not simply a piece of re-bar inserted into it. If the project is an engineered beam (glulam or microlam?) are the viability periods for those out past 100 years?

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

RE: Considerations for sealing wood beams for ground contact

Lateral loads on the posts would be taken with beams bolted to the posts just above the concrete similar to a sill plate in a framed house except they are on edge instead of flat. Bending loads induced by wind loads across the barn would be taken by the roof trusses with triangular beams from the trusses to the posts. Lots of triangles are good things in a barn design. We live in upstate NY at an elevation of 1140 ft. MSL and it is frequently very windy: 55 + MPH. Our barn is 25' x 40' with the 25 ft. end facing the westerly winds. So far we have had no problems with the structure including a minor earthquake.

Bob Price
A*G*M

RE: Considerations for sealing wood beams for ground contact

Quote (RBPrice)

Do not put the posts into the ground but support them on concrete pillars poured into one of the proprietary cardboard tubes like "Sonotube" obtainable from Lowes or Home Depot. Put a 15 inch length of rebar in the top of each post with 8 inches into the post, trowel a slight radius to help shed water, use pressure treated lumber and the barn will last several hundred years. Lay out the location with a transit and string and hire a back hoe with a rotary drill attachment to drill the holes.

Note that your local building code will probably require that either the bare posts or the concrete columns will have to go down four feet to keep them from frost heaving. Mine are only six years old but I suspect my great grand children will have to auction the barn off.

Bob Price

That is how (with the exception of the sonotubes) the overhang on my Mother's barn was supported. The house is 200 years old but the barn is newer, probably only ~100 years old. We had to replace one of the corner support posts last year because the gutter downspout had rusted out and was letting the water run down the post. If that had been maintained properly the post would still be as good as the others. Had to jack up that corner of the barn and replace the 12" square by 8' long post. We used solid oak. This post won't take any bending loads.

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RE: Considerations for sealing wood beams for ground contact

Our 1850 pegged oak beam barn rebuild recently used those 36" deep 12" dia sonitube cement supports with short rebar into the 8" sq oak 12' verticals for the extended overhang wall support. But the huge weight of this solid oak beam full size barn w/ 1" thick batten board siding I think allows this above ground cement to wood joint on one side - more like a porch overhang....

But our 40x60'x20'h pole barn with metal siding weighs NOTHING. Such a joint in OH winds would simply blow it away! It is like a sailing ship. There is no way I would ever even contemplate anything less than solid cca treated 8x8 BURIED below frost line timber for the vertical supports. If you any less you will not have to worry about it standing 100yrs!

www.KilroyWasHere<dot>com

RE: Considerations for sealing wood beams for ground contact

Quote:

and then I need to design and fab specialty splice plates to join to wood above ground. Still just not sure if it is worth all tha

Or just use one of the many commercially available connectors that are made exactly for this situation. This one for example: http://www.strongtie.com/products/connectors/cbsq....

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